[VB6] - animated gif function errors:(

[jmsrickland]

What do you mean by aren't correct? If the GIF images has an images (by double clicking on it in your folder) then it's a correct GIF image. Give me an example of one that isn't correct

[joaquim]

What do you mean by aren't correct? If the GIF images has an images (by double clicking on it in your folder) then it's a correct GIF image. Give me an example of one that isn't correct

if is, always, '1', how i know that from frame #1 to frame#2 isn't changed?
these example have 5 frames:
0 - normal frame;
1 - need the last one for be completed;
2 and 3 - new frames(it's completed, don't need the last frame);
4 and 5 - need the last frame.

[jmsrickland]

I don't understand your numbers 0, 1, 2, 3, 4, 5

There are only four disposal codes: 0, 1, 2, and 3.

The image I tested has all frames with a disposal value of 1 = LEAVE

[joaquim]

sorry... i will express better:

frame #0 -> don't need the disposal value, because it's the 1st frame;
frame #1 ->needs the last frame to be completed... disposal value is '1'(correct). Frame #0 + transparent Frame #1;
frame #2 -> it's a new frame. don't needs a disposal method, but we recive '1'... it's incorrect!!!;
frame #3 -> it's a new frame. don't needs a disposal method, but we recive '1'... it's incorrect!!!;
frame #4 ->needs the last frame to be completed... disposal value is '1'(correct). Frame #3 + transparent Frame #4;
frame #5 ->needs the last frame to be completed... disposal value is '1'(correct). Frame #4(now that these frame is completed) + transparent Frame #5.

sorry if my english is bad, but now i think that you know what i mean(using the halloween image for the test).

[joaquim]

i'm testing the disposal values:

TotalFrames = aImg.Count - 1
    LoadGif = True
    Load aImg(imgCount - 1)
    For i = 1 To TotalFrames
        If intDisposed(i) = 0 Then
            'do nothing
        ElseIf intDisposed(i) = 1 Then
            aImg(aImg.Count - 1).Picture = aImg(i - 1).Image
            Debug.Print TransparentBlt(aImg(aImg.Count - 1).hdc, 0, 0, aImg(i - 1).ScaleWidth, aImg(i - 1).ScaleHeight, aImg(i).hdc, 0, 0, aImg(i - 1).ScaleWidth, aImg(i - 1).ScaleHeight, GetPixel(aImg(i).hdc, 0, 0))
            aImg(i).Picture = aImg(aImg.Count - 1).Image
            aImg(aImg.Count - 1).Cls
        End If
    Next i
    aImg(aImg.Count - 1) = Nothing
    'Unload aImg.Count - 1
    Debug.Print aImg.Count - 1
    Exit Function

but i see some errors:
1 - the transparentblt() api function don't do the job(i think is the Load method), because i recive false;
2 - i can't unload the last image control that i create for these test
any advice my friend?
thanks

[joaquim]

ok... now works

If aImg.Count >= 2 Then
        Load aImg(aImg.Count)
        For i = 1 To aImg.Count - 2
            If i = 0 Then
                'nothing
            ElseIf intDisposed(i) = 1 Then
                'previous frame + actual frame(transparent) = result frame
                aImg(aImg.Count - 1).Picture = Nothing
                aImg(aImg.Count - 1).Picture = aImg(i - 1).Image
                TransparentBlt aImg(aImg.Count - 1).hdc, aImg(0).ScaleWidth \ 2 - aImg(i).ScaleWidth \ 2, aImg(0).ScaleHeight \ 2 - aImg(i).ScaleHeight \ 2, aImg(i).ScaleWidth, aImg(i).ScaleHeight, aImg(i).hdc, 0, 0, aImg(i).ScaleWidth, aImg(i).ScaleHeight, GetPixel(aImg(i).hdc, 0, 0)
                aImg(i).Picture = Nothing
                aImg(i).Picture = aImg(aImg.Count - 1).Image
            End If
        Next i
        Unload aImg(aImg.Count - 1)
    End If

my problem is the TransparentBlt () destionation position: aImg(0).ScaleWidth \ 2 - aImg(i).ScaleWidth \ 2, aImg(0).ScaleHeight \ 2 - aImg(i).ScaleHeight \ 2, aImg(i).ScaleWidth (X,Y). because i can't put it on center

[jmsrickland]

sorry... i will express better:

frame #0 -> don't need the disposal value, because it's the 1st frame;
frame #1 ->needs the last frame to be completed... disposal value is '1'(correct). Frame #0 + transparent Frame #1;
frame #2 -> it's a new frame. don't needs a disposal method, but we recive '1'... it's incorrect!!!;
frame #3 -> it's a new frame. don't needs a disposal method, but we recive '1'... it's incorrect!!!;
frame #4 ->needs the last frame to be completed... disposal value is '1'(correct). Frame #3 + transparent Frame #4;
frame #5 ->needs the last frame to be completed... disposal value is '1'(correct). Frame #4(now that these frame is completed) + transparent Frame #5.

sorry if my english is bad, but now i think that you know what i mean(using the halloween image for the test).

I dissagree. I think they are correct.

If you think they are incorrect then tell me what you think the value should be.

[jmsrickland]

i'm testing the disposal values:

TotalFrames = aImg.Count - 1
    LoadGif = True
    Load aImg(imgCount - 1)
    For i = 1 To TotalFrames
        If intDisposed(i) = 0 Then
            'do nothing
        ElseIf intDisposed(i) = 1 Then
            aImg(aImg.Count - 1).Picture = aImg(i - 1).Image
            Debug.Print TransparentBlt(aImg(aImg.Count - 1).hdc, 0, 0, aImg(i - 1).ScaleWidth, aImg(i - 1).ScaleHeight, aImg(i).hdc, 0, 0, aImg(i - 1).ScaleWidth, aImg(i - 1).ScaleHeight, GetPixel(aImg(i).hdc, 0, 0))
            aImg(i).Picture = aImg(aImg.Count - 1).Image
            aImg(aImg.Count - 1).Cls
        End If
    Next i
    aImg(aImg.Count - 1) = Nothing
    'Unload aImg.Count - 1
    Debug.Print aImg.Count - 1
    Exit Function

but i see some errors:
1 - the transparentblt() api function don't do the job(i think is the Load method), because i recive false;
2 - i can't unload the last image control that i create for these test
any advice my friend?
thanks

I don't see any TransparentBlt API in that code you sent me. Are you now using some other code?

[joaquim]

I don't see any TransparentBlt API in that code you sent me. Are you now using some other code?

now, in same function, i'm use the disposal values

If aImg.Count >= 2 Then
        Load aImg(aImg.Count)
        aImg(imgCount - 1).Width = aImg(imgCount - 2).Width
        aImg(imgCount - 1).Height = aImg(imgCount - 2).Height
        For i = 1 To aImg.Count - 2
            If i = 0 Then
                'nothing
            ElseIf intDisposed(i) = 1 Then
                'previous frame + actual frame(transparent) = result frame
                aImg(aImg.Count - 1).Picture = Nothing
                aImg(aImg.Count - 1).Picture = aImg(i - 1).Image
                TransparentBlt aImg(aImg.Count - 1).hdc, aImg(i - 1).Width / 2 - aImg(i).Width / 2, aImg(i - 1).Height / 2 - aImg(i).Height / 2, aImg(i - 1).Width, aImg(i - 1).Height, aImg(i).hdc, 0, 0, aImg(i).ScaleWidth, aImg(i).ScaleHeight, GetPixel(aImg(i).hdc, 0, 0)
                aImg(i).Picture = Nothing
                aImg(i).Picture = aImg(aImg.Count - 1).Image
            End If
        Next i
        Unload aImg(aImg.Count - 1)
    End If

but i have 1 position error here:

TransparentBlt aImg(aImg.Count - 1).hdc, aImg(i - 1).Width / 2 - aImg(i).Width / 2, aImg(i - 1).Height / 2 - aImg(i).Height / 2, aImg(i - 1).Width, aImg(i - 1).Height, aImg(i).hdc, 0, 0, aImg(i).ScaleWidth, aImg(i).ScaleHeight, GetPixel(aImg(i).hdc, 0, 0)

i must put all frames on middle of last one for be drawed correctly. but my code isn't right... can you advice me?

[jmsrickland]

I can't because that code your are posting is not in the code you sent me, That's what I asked you before but you didn't respond .

[joaquim]

I can't because that code your are posting is not in the code you sent me, That's what I asked you before but you didn't respond .

 'Method Values :
             '0 -   No disposal specified. The decoder is _
                    not required to take any action.
                    
             '1 -   Do not dispose. The graphic is to be left _
                    in place.
                    
             '2 -   Restore to background color. The area used by the _
                    graphic must be restored to the background color.
                    
             '3 -   Restore to previous. The decoder is required to _
                    restore the area overwritten by the graphic with _
                    what was there prior to rendering the graphic.
            '4-7 -  To be defined.

Option Explicit

Public Enum GifType
    GIF87A = 0
    GIF89A = 1
End Enum

Private Declare Function TransparentBlt Lib "msimg32.dll" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal nSrcWidth As Long, ByVal nSrcHeight As Long, ByVal crTransparent As Long) As Boolean
Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long) As Long

Public RepeatTimes As Long 'This one calculates,
' but don't use in this sample. If You need, You
' can add simple checking at Timer1_Timer Procedure
Public TotalFrames As Long
Public GifTypeFile As GifType

Public Function LoadGif(sFile As String, aImg As Variant) As Boolean
    If Dir$(sFile) = "" Or sFile = "" Then
       MsgBox "File " & sFile & " not found", vbCritical
       Exit Function
    End If
    
    If Mid$(UCase(sFile), Len(sFile) - 2, 3) <> "GIF" Then Exit Function
    
    'On Error GoTo ErrHandler
    'On Error Resume Next
    Dim fNum As Integer
    Dim imgHeader As String, fileHeader As String
    Dim buf$, picbuf$
    Dim imgCount As Integer
    Dim i&, j&, xOff&, yOff&, TimeWait&
    Dim GifEnd As String
    Dim intDisposed() As Integer
    Dim intHeight As Integer
    Dim intWidth As Integer
    
    GifEnd = Chr(0) & Chr(33) & Chr(249) '<---only for animated GIF's
    
    For i = 1 To aImg.Count - 1
        Unload aImg(i)
    Next i
    
    fNum = FreeFile
    Open sFile For Binary Access Read As fNum
        buf = String(LOF(fNum), Chr(0))
        Get #fNum, , buf 'Get GIF File into buffer
    Close fNum
    
    i = 1
    imgCount = 0
    
    j = InStr(1, buf, GifEnd) + 1   '<---  j = 1 or 0 if not a animated gif ---- j > 1 if it is an animated gif
    
    If j < 2 Then
      aImg(0).Picture = LoadPicture(sFile)
      TotalFrames = aImg.Count - 1
      aImg(0).Tag = 0
      LoadGif = True
      Exit Function
    End If
    
    fileHeader = Left(buf, j)
    
    If Left$(fileHeader, 1) <> "G" Then
       MsgBox "This file is not a *.gif file", vbCritical
       Exit Function
    End If
    
    'Get gif type
    'intWidth = Asc(Mid$(fileHeader, 7, 4))
    'intHeight = Asc(Mid$(fileHeader, 9, 4))
    frmTest.BackColor = Asc(Mid$(fileHeader, 12, 1))
    If Left$(fileHeader, 6) = "GIF89a" Then
        GifTypeFile = GIF89A
    Else
        GifTypeFile = GIF87A
    End If
        
    LoadGif = True
    i = j + 2
    If Len(fileHeader) >= 127 Then
        RepeatTimes& = Asc(Mid(fileHeader, 126, 1)) + (Asc(Mid(fileHeader, 127, 1)) * 256&)
    Else
        RepeatTimes = 0
    End If

    Do ' Split GIF Files at separate pictures
       ' and load them into Image Array
        imgCount = imgCount + 1
        j = InStr(i, buf, GifEnd) + 3
        If j > Len(GifEnd) Then
            fNum = FreeFile
            Open "temp.gif" For Binary As fNum
                picbuf = String(Len(fileHeader) + j - i, Chr(0))
                picbuf = fileHeader & Mid(buf, i - 1, j - i)
                Put #fNum, 1, picbuf
                imgHeader = Left(Mid(buf, i - 1, j - i), 16)
            Close fNum
            TimeWait = ((Asc(Mid(imgHeader, 4, 1))) + (Asc(Mid(imgHeader, 5, 1)) * 256&)) * 10&
            If imgCount > 1 Then
                xOff = Asc(Mid(imgHeader, 9, 1)) + (Asc(Mid(imgHeader, 10, 1)) * 256&)
                yOff = Asc(Mid(imgHeader, 11, 1)) + (Asc(Mid(imgHeader, 12, 1)) * 256&)
                Load aImg(imgCount - 1)
                'aImg(imgCount - 1).Width = intWidth '\ Screen.TwipsPerPixelX
                'aImg(imgCount - 1).Height = intHeight '\ Screen.TwipsPerPixelY
                'aImg(imgCount - 1).Left = aImg(0).Left + (xOff * Screen.TwipsPerPixelX)
                'aImg(imgCount - 1).Top = aImg(0).Top + (yOff * Screen.TwipsPerPixelY)
            End If
            ' Use .Tag Property to save TimeWait interval for separate Image
            aImg(imgCount - 1).Tag = TimeWait
            aImg(imgCount - 1).Picture = LoadPicture("temp.gif")
            ReDim Preserve intDisposed(aImg.Count - 1)
            intDisposed(aImg.Count - 1) = Asc(Mid(imgHeader, 3, 1)) / 4 And 3

            Kill ("temp.gif")
            i = j
        End If
        'DoEvents
    Loop Until j = 3
    
    ' If there are one more Image - Load it
    If i < Len(buf) Then
        fNum = FreeFile
        Open "temp.gif" For Binary As fNum
            picbuf = String(Len(fileHeader) + Len(buf) - i, Chr(0))
            picbuf = fileHeader & Mid(buf, i - 1, Len(buf) - i)
            Put #fNum, 1, picbuf
            imgHeader = Left(Mid(buf, i - 1, Len(buf) - i), 16)
        Close fNum
        TimeWait = ((Asc(Mid(imgHeader, 4, 1))) + (Asc(Mid(imgHeader, 5, 1)) * 256)) * 10
        If imgCount > 1 Then
            xOff = Asc(Mid(imgHeader, 9, 1)) + (Asc(Mid(imgHeader, 10, 1)) * 256)
            yOff = Asc(Mid(imgHeader, 11, 1)) + (Asc(Mid(imgHeader, 12, 1)) * 256)
            Load aImg(imgCount - 1)
            'aImg(imgCount - 1).Width = intWidth '\ Screen.TwipsPerPixelX
            'aImg(imgCount - 1).Height = intHeight '\ Screen.TwipsPerPixelY
            'aImg(imgCount - 1).Left = aImg(0).Left + (xOff * Screen.TwipsPerPixelX)
            'aImg(imgCount - 1).Top = aImg(0).Top + (yOff * Screen.TwipsPerPixelY)
        End If
        aImg(imgCount - 1).Tag = TimeWait
        aImg(imgCount - 1).Picture = LoadPicture("temp.gif")
        ReDim Preserve intDisposed(aImg.Count - 1)
        intDisposed(aImg.Count - 1) = Asc(Mid(imgHeader, 3, 1)) / 4 And 3
        Kill ("temp.gif")
    End If
    TotalFrames = aImg.Count - 1
    LoadGif = True
    If aImg.Count >= 2 Then
        Load aImg(aImg.Count)
        aImg(imgCount - 1).Width = aImg(imgCount - 2).Width
        aImg(imgCount - 1).Height = aImg(imgCount - 2).Height
        For i = 1 To aImg.Count - 2
            If i = 0 Then
                'nothing
            ElseIf intDisposed(i) = 1 Then
                'previous frame + actual frame(transparent) = result frame
                aImg(aImg.Count - 1).Picture = Nothing
                aImg(aImg.Count - 1).Picture = aImg(i - 1).Image
                TransparentBlt aImg(aImg.Count - 1).hdc, aImg(0).Width / 2 - aImg(i).Width / 2, aImg(0).Height / 2 - aImg(i).Height / 2, aImg(i - 1).Width, aImg(i - 1).Height, aImg(i).hdc, 0, 0, aImg(i).ScaleWidth, aImg(i).ScaleHeight, GetPixel(aImg(i).hdc, 0, 0)
                aImg(i).Picture = Nothing
                aImg(i).Picture = aImg(aImg.Count - 1).Image
            End If
        Next i
        Unload aImg(aImg.Count - 1)
    End If
    
    Exit Function
ErrHandler:
 MsgBox "Error No. " & Err.Number & " when reading file", vbCritical
 LoadGif = False
 On Error GoTo 0
End Function

[jmsrickland]

Why are you messing around with the TransparentBLT API? Doesn't loading the Image controls already support transparency?

[jmsrickland]

All frames have their own positioning control codes. Look at the format I posted in post #23

Each frame has the following header

Y Pos of frame --------------------------+
X Pos of frame --------------------+     | 
                                   |     |
21 F9 | 04 | 05 32 00 09 00 | 2C | 00 00 00 00 | 13 00 | 19 00 |

[joaquim]

Why are you messing around with the TransparentBLT API? Doesn't loading the Image controls already support transparency?

i don't miss. i'm building a complete frame on same picturebox(fro show the correct frame)
let me ask you 1 thing:
like you know, i can see the image size correctly... the values are in pixel. then how can i change the picturebox size from container scalemode?

[jmsrickland]

You want the picturebox to have the size of the container's scalemode? Am I understanding you correctly?

I'm assuming the container is the Form on which the picturebox is.

Picture1.ScaleMode = Form1.ScaleMode
Picture1.ScaleWidth = Form1.ScaleWidth
Picture1.ScaleHeight = Form1.ScaleHeight

[jmsrickland]

I have question for you

If you are trying to make this GIF application on a regular Form and you are using the Image control to show the different frames then the Image control already has transparency so I don't understand why you need to deal with the TransparentBlt API. If you are trying to do this on a User Control then you are not going to get any transparency at all using Image or Picture controls; it won't work even if you use the TransparentBlt API. The only way to get transparency on a User Control is to draw the pictures directly on the UC window. Is this what you are doing?

[joaquim]

I have question for you

If you are trying to make this GIF application on a regular Form and you are using the Image control to show the different frames then the Image control already has transparency so I don't understand why you need to deal with the TransparentBlt API. If you are trying to do this on a User Control then you are not going to get any transparency at all using Image or Picture controls; it won't work even if you use the TransparentBlt API. The only way to get transparency on a User Control is to draw the pictures directly on the UC window. Is this what you are doing?

i will try express me
my last for..next is for compare the disposal values, like you have seen. but thinking in these way: if the frame#1=frame#0 + transparent frame#1, why not show it completed in same picturebox(i have change it)!?! is what i do in last for..next loop
then, when you show the images, you don't need to horry about disposal values

[joaquim]

You want the picturebox to have the size of the container's scalemode? Am I understanding you correctly?

I'm assuming the container is the Form on which the picturebox is.

Picture1.ScaleMode = Form1.ScaleMode
Picture1.ScaleWidth = Form1.ScaleWidth
Picture1.ScaleHeight = Form1.ScaleHeight

sorry no. think in these way:
form1.scalemode=vbtwips
picture1.scalemode=vbpixels
you know that image size is in pixels
then how you can resize the picture1(i always have these problem)?
imagine:
imagewidth=100 pixels
imageheight=50 pixels
you can't do:
picture1.width=100
picture1.height=50
because the picture size is more small than image size
i need convert the values to form(container) scalemode.
i'm trying correct the transparentblt() destination position

[jmsrickland]

sorry no. think in these way:
form1.scalemode=vbtwips
picture1.scalemode=vbpixels
you know that image size is in pixels
then how you can resize the picture1(i always have these problem)?
imagine:
imagewidth=100 pixels
imageheight=50 pixels
you can't do:
picture1.width=100
picture1.height=50
because the picture size is more small than image size
i need convert the values to form(container) scalemode.
i'm trying correct the transparentblt() destination position

First, The Form ScaleMode has nothing to do with your Picture box ScaleMode but just for convenience sake then change your FormScaleMode = vbPixels. Why are you even using Twips?

Second, Your Picture box is already in Pixels and how you deal with it has nothing to do with the Form or the Form's ScaleMode.

If you are putting a picture in a Picture box by loading it (LoadPicture for example) then if your Picture box has it's AutoSize = True it will resize for you. If you are putting a picture in the Picture use BitBlt then you need to do your own resizing. So, you say the image itself is 100 by 50 pixels, right. Change your Picture box to have no border around it; Picture1.Appearance = 0 and Picture1.BorderStyle = 0. Now you can make your changes

Picture1.Width=100
Picture1.Height=50

[jmsrickland]

i will try express me
my last for..next is for compare the disposal values, like you have seen. but thinking in these way: if the frame#1=frame#0 + transparent frame#1, why not show it completed in same picturebox(i have change it)!?! is what i do in last for..next loop
then, when you show the images, you don't need to horry about disposal values

This one I don't understand what you are doing. Why are you using Picture boxes? They don't have transparency.

[joaquim]

This one I don't understand what you are doing. Why are you using Picture boxes? They don't have transparency.

i know my friend. my objective is combine the frames(for show the corrected frame).
but my big objective is use these code for update my sprite control. i'm update it for read more gif files, and make the graphics effects more faster(i'm building the Graphic class too hehehe
can you just advice on transparentblt() api function?
i know that works fine, but the positions aren't correct

[jmsrickland]

I don't know which project you are working on so send me the project that you are currently working on with the TransparentBlt problem and only the gif file you are trying to position. I see what I can do.

[joaquim]

heres the code updated:

'Method Values :
             '0 -   No disposal specified. The decoder is _
                    not required to take any action.
                    
             '1 -   Do not dispose. The graphic is to be left _
                    in place.
                    
             '2 -   Restore to background color. The area used by the _
                    graphic must be restored to the background color.
                    
             '3 -   Restore to previous. The decoder is required to _
                    restore the area overwritten by the graphic with _
                    what was there prior to rendering the graphic.
            '4-7 -  To be defined.

Option Explicit

Private Type DisposedValues
    Disposed As Integer
    FrameXPos As Long
    FrameYPos As Long
End Type

Public Enum GifType
    GIF87A = 0
    GIF89A = 1
End Enum

Private Declare Function TransparentBlt Lib "msimg32.dll" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal nSrcWidth As Long, ByVal nSrcHeight As Long, ByVal crTransparent As Long) As Boolean
Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long
Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long) As Long

Public RepeatTimes As Long 'This one calculates,
' but don't use in this sample. If You need, You
' can add simple checking at Timer1_Timer Procedure
Public TotalFrames As Long
Public GifTypeFile As GifType
Public Dispose() As DisposedValues

Public Function LoadGif(sFile As String, aImg As Variant) As Boolean
    If Dir$(sFile) = "" Or sFile = "" Then
       MsgBox "File " & sFile & " not found", vbCritical
       Exit Function
    End If
    
    If Mid$(UCase(sFile), Len(sFile) - 2, 3) <> "GIF" Then Exit Function
    
    'On Error GoTo ErrHandler
    'On Error Resume Next
    Dim fNum As Integer
    Dim imgHeader As String, fileHeader As String
    Dim buf$, picbuf$
    Dim imgCount As Integer
    Dim i&, j&, FrameX&, FrameY&, TimeWait&
    Dim GifEnd As String
    Dim intDisposed() As Integer
    Dim intHeight As Integer
    Dim intWidth As Integer
    
    GifEnd = Chr(0) & Chr(33) & Chr(249) '<---only for animated GIF's
    
    'unload all pictureboxes\images
    For i = 1 To aImg.Count - 1
        Unload aImg(i)
    Next i
    
    'Get GIF File into buffer
    fNum = FreeFile
    Open sFile For Binary Access Read As fNum
        buf = String(LOF(fNum), Chr(0))
        Get #fNum, , buf
    Close fNum
    
    i = 1
    imgCount = 0
    
    j = InStr(1, buf, GifEnd) + 1   '<---  j = 1 or 0 if not a animated gif ---- j > 1 if it is an animated gif
    
    'if the Gif isn't animated
    'then just show the image
    If j < 2 Then
      aImg(0).Picture = LoadPicture(sFile)
      TotalFrames = aImg.Count - 1
      aImg(0).Tag = 0
      LoadGif = True
      Exit Function
    End If
    
    fileHeader = Left(buf, j)
    
    'if the file is gif structure
    If Left$(fileHeader, 1) <> "G" Then
       MsgBox "This file is not a *.gif file", vbCritical
       Exit Function
    End If
    LoadGif = True
    
    'Get gif type
    'intWidth = Asc(Mid$(fileHeader, 7, 4))
    'intHeight = Asc(Mid$(fileHeader, 9, 4))
    'BackColor = Asc(Mid$(fileHeader, 11, 1))
    
    'Gif Type
    If Left$(fileHeader, 6) = "GIF89a" Then
        GifTypeFile = GIF89A
    Else
        GifTypeFile = GIF87A
    End If
        
    
    i = j + 2
    
    'how many times the animation is repeated
    If Len(fileHeader) >= 127 Then
        RepeatTimes& = Asc(Mid(fileHeader, 126, 1)) + (Asc(Mid(fileHeader, 127, 1)) * 256&)
    Else
        RepeatTimes = 0
    End If

    Do
        ' Split GIF Files at separate pictures
        ' and load them into Image Array
        imgCount = imgCount + 1
        j = InStr(i, buf, GifEnd) + 3
        If j > Len(GifEnd) Then
            fNum = FreeFile
            Open "temp.gif" For Binary As fNum
                picbuf = String(Len(fileHeader) + j - i, Chr(0))
                picbuf = fileHeader & Mid(buf, i - 1, j - i)
                Put #fNum, 1, picbuf
                imgHeader = Left(Mid(buf, i - 1, j - i), 16)
            Close fNum
            
            'frame delay time
            TimeWait = ((Asc(Mid(imgHeader, 4, 1))) + (Asc(Mid(imgHeader, 5, 1)) * 256&)) * 10&
            
            If imgCount > 1 Then
                'Get frame position
                FrameX = Asc(Mid(imgHeader, 9, 1)) + (Asc(Mid(imgHeader, 10, 1)) * 256&)
                FrameY = Asc(Mid(imgHeader, 11, 1)) + (Asc(Mid(imgHeader, 12, 1)) * 256&)
                
                'load control for show the image
                Load aImg(imgCount - 1)
                
                'change the control position
                'for show the image in right position
                aImg(imgCount - 1).Left = FrameX * Screen.TwipsPerPixelX
                aImg(imgCount - 1).Top = FrameY * Screen.TwipsPerPixelY
            End If
            ' Use .Tag Property to save TimeWait interval for separate Image
            aImg(imgCount - 1).Tag = TimeWait
            aImg(imgCount - 1).Picture = LoadPicture("temp.gif")
            
            'Get the disposal values and positions from frames
            ReDim Preserve Dispose(aImg.Count - 1)
            Dispose(aImg.Count - 1).Disposed = Asc(Mid(imgHeader, 3, 1)) / 4 And 3
            Dispose(aImg.Count - 1).FrameXPos = FrameX
            Dispose(aImg.Count - 1).FrameYPos = FrameY
            
            'kill temp file
            Kill ("temp.gif")
            i = j
        End If
        'DoEvents
    Loop Until j = 3
    
    ' If there are one more Image - Load it
    If i < Len(buf) Then
        fNum = FreeFile
        Open "temp.gif" For Binary As fNum
            picbuf = String(Len(fileHeader) + Len(buf) - i, Chr(0))
            picbuf = fileHeader & Mid(buf, i - 1, Len(buf) - i)
            Put #fNum, 1, picbuf
            imgHeader = Left(Mid(buf, i - 1, Len(buf) - i), 16)
        Close fNum
        TimeWait = ((Asc(Mid(imgHeader, 4, 1))) + (Asc(Mid(imgHeader, 5, 1)) * 256)) * 10
        If imgCount > 1 Then
            FrameX = Asc(Mid(imgHeader, 9, 1)) + (Asc(Mid(imgHeader, 10, 1)) * 256)
            FrameY = Asc(Mid(imgHeader, 11, 1)) + (Asc(Mid(imgHeader, 12, 1)) * 256)
            Load aImg(imgCount - 1)
            aImg(imgCount - 1).Left = FrameX * Screen.TwipsPerPixelX
            aImg(imgCount - 1).Top = FrameY * Screen.TwipsPerPixelY
        End If
        aImg(imgCount - 1).Tag = TimeWait
        aImg(imgCount - 1).Picture = LoadPicture("temp.gif")
        ReDim Preserve Dispose(aImg.Count - 1)
        Dispose(aImg.Count - 1).Disposed = Asc(Mid(imgHeader, 3, 1)) / 4 And 3
        Dispose(aImg.Count - 1).FrameXPos = FrameX
        Dispose(aImg.Count - 1).FrameYPos = FrameY
        Kill ("temp.gif")
    End If
    TotalFrames = aImg.Count - 1
    LoadGif = True
    If aImg.Count >= 2 Then
        Load aImg(aImg.Count)
        aImg(aImg.Count - 1).Width = aImg(0).Width
        aImg(aImg.Count - 1).Height = aImg(0).Height
        For i = 1 To aImg.Count - 2
            If Dispose(i).Disposed = 0 Then
                'nothing
            ElseIf Dispose(i).Disposed = 1 Then
                'previous frame + actual frame(transparent) = result frame
                aImg(aImg.Count - 1).Picture = aImg(i - 1).Image
                Debug.Print TransparentBlt(aImg(aImg.Count - 1).hdc, Dispose(i).FrameXPos, Dispose(i).FrameYPos, aImg(i).ScaleWidth, aImg(i).ScaleHeight, aImg(i).hdc, 0, 0, aImg(i).ScaleWidth, aImg(i).ScaleHeight, GetPixel(aImg(i).hdc, 0, 0))
                aImg(i).Picture = aImg(aImg.Count - 1).Image
                aImg(i).Left = FrameX * Screen.TwipsPerPixelX
                aImg(i).Top = FrameY * Screen.TwipsPerPixelY
                aImg(aImg.Count - 1).Cls
            End If
        Next i
        Unload aImg(aImg.Count - 1)
    End If
    LoadGif = True
    Exit Function
ErrHandler:
 MsgBox "Error No. " & Err.Number & " when reading file", vbCritical
 LoadGif = False
 On Error GoTo 0
End Function

the frame 0 position isn't correct. how can i get it?

[jmsrickland]

heres the code updated:
the frame 0 position isn't correct. how can i get it?

Here's what you do

1) Set Form ScaleMode = vbPixels
2) Change Image1(0) to appearance flat and BorderStyle none
3) Add another Picture box control (Picture2)
4) Set it's ScaleMode to vbPixels
5) Cut and Paste Image1(0) inside of Picture2
6) Change code as below

Private Sub Command1_Click()
  Timer1.Enabled = False
  CommonDialog1.ShowOpen
  If LoadGif(CommonDialog1.FileName, image1) = False Then Exit Sub
    
  Picture2.Width = image1(0).Width + 4
  Picture2.Height = image1(0).Height + 4
     
     FrameCount = 0
     Timer1.Interval = image1(0).Tag
     Timer1.Enabled = True
  image1(0).Visible = True
End Sub

In the .BAS module change code

'Method Values :
             '0 -   No disposal specified. The decoder is _
                    not required to take any action.
                    
             '1 -   Do not dispose. The graphic is to be left _
                    in place.
                    
             '2 -   Restore to background color. The area used by the _
                    graphic must be restored to the background color.
                    
             '3 -   Restore to previous. The decoder is required to _
                    restore the area overwritten by the graphic with _
                    what was there prior to rendering the graphic.
            '4-7 -  To be defined.

Option Explicit

Private Type DisposedValues
    Disposed As Integer
    FrameXPos As Long
    FrameYPos As Long
End Type

Public Enum GifType
    GIF87A = 0
    GIF89A = 1
End Enum

Private Declare Function TransparentBlt Lib "msimg32.dll" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal nSrcWidth As Long, ByVal nSrcHeight As Long, ByVal crTransparent As Long) As Boolean
Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long
Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long) As Long

Public RepeatTimes As Long 'This one calculates,
' but don't use in this sample. If You need, You
' can add simple checking at Timer1_Timer Procedure
Public TotalFrames As Long
Public GifTypeFile As GifType
Public Dispose() As DisposedValues

Public Function LoadGif(sFile As String, aImg As Variant) As Boolean
    If Dir$(sFile) = "" Or sFile = "" Then
       MsgBox "File " & sFile & " not found", vbCritical
       Exit Function
    End If
    
    If Mid$(UCase(sFile), Len(sFile) - 2, 3) <> "GIF" Then Exit Function
    
    'On Error GoTo ErrHandler
    'On Error Resume Next
    Dim fNum As Integer
    Dim imgHeader As String, fileHeader As String
    Dim buf$, picbuf$
    Dim imgCount As Integer
    Dim i&, j&, FrameX&, FrameY&, TimeWait&
    Dim GifEnd As String
    Dim intDisposed() As Integer
    Dim intHeight As Integer
    Dim intWidth As Integer
    
    GifEnd = Chr(0) & Chr(33) & Chr(249) '<---only for animated GIF's
    
    'unload all pictureboxes\images
    For i = 1 To aImg.Count - 1
        Unload aImg(i)
    Next i
    
    'Get GIF File into buffer
    fNum = FreeFile
    Open sFile For Binary Access Read As fNum
        buf = String(LOF(fNum), Chr(0))
        Get #fNum, , buf
    Close fNum
    
    i = 1
    imgCount = 0
    
    j = InStr(1, buf, GifEnd) + 1   '<---  j = 1 or 0 if not a animated gif ---- j > 1 if it is an animated gif
    
    'if the Gif isn't animated
    'then just show the image
    If j < 2 Then
      aImg(0).Picture = LoadPicture(sFile)
      TotalFrames = aImg.Count - 1
      aImg(0).Tag = 0
      LoadGif = True
      Exit Function
    End If
    
    fileHeader = Left(buf, j)
    
    'if the file is gif structure
    If Left$(fileHeader, 1) <> "G" Then
       MsgBox "This file is not a *.gif file", vbCritical
       Exit Function
    End If
    LoadGif = True
    
    'Get gif type
    'intWidth = Asc(Mid$(fileHeader, 7, 4))
    'intHeight = Asc(Mid$(fileHeader, 9, 4))
    'BackColor = Asc(Mid$(fileHeader, 11, 1))
    
    'Gif Type
    If Left$(fileHeader, 6) = "GIF89a" Then
        GifTypeFile = GIF89A
    Else
        GifTypeFile = GIF87A
    End If
        
    
    i = j + 2
    
    'how many times the animation is repeated
    If Len(fileHeader) >= 127 Then
        RepeatTimes& = Asc(Mid(fileHeader, 126, 1)) + (Asc(Mid(fileHeader, 127, 1)) * 256&)
    Else
        RepeatTimes = 0
    End If

    Do
        ' Split GIF Files at separate pictures
        ' and load them into Image Array
        imgCount = imgCount + 1
        j = InStr(i, buf, GifEnd) + 3
        If j > Len(GifEnd) Then
            fNum = FreeFile
            Open "temp.gif" For Binary As fNum
                picbuf = String(Len(fileHeader) + j - i, Chr(0))
                picbuf = fileHeader & Mid(buf, i - 1, j - i)
                Put #fNum, 1, picbuf
                imgHeader = Left(Mid(buf, i - 1, j - i), 16)
            Close fNum
            
            'frame delay time
            TimeWait = ((Asc(Mid(imgHeader, 4, 1))) + (Asc(Mid(imgHeader, 5, 1)) * 256&)) * 10&
            
            If imgCount > 1 Then
                'Get frame position
                FrameX = Asc(Mid(imgHeader, 9, 1)) + (Asc(Mid(imgHeader, 10, 1)) * 256&)
                FrameY = Asc(Mid(imgHeader, 11, 1)) + (Asc(Mid(imgHeader, 12, 1)) * 256&)
                
                'load control for show the image
                Load aImg(imgCount - 1)
                
                'change the control position
                'for show the image in right position
                aImg(imgCount - 1).Left = FrameX '* Screen.TwipsPerPixelX
                aImg(imgCount - 1).Top = FrameY '* Screen.TwipsPerPixelY
            End If
            ' Use .Tag Property to save TimeWait interval for separate Image
            aImg(imgCount - 1).Tag = TimeWait
            aImg(imgCount - 1).Picture = LoadPicture("temp.gif")
            
            'Get the disposal values and positions from frames
            ReDim Preserve Dispose(aImg.Count - 1)
            Dispose(aImg.Count - 1).Disposed = Asc(Mid(imgHeader, 3, 1)) / 4 And 3
            Dispose(aImg.Count - 1).FrameXPos = FrameX
            Dispose(aImg.Count - 1).FrameYPos = FrameY
            
            'kill temp file
            Kill ("temp.gif")
            i = j
        End If
        'DoEvents
    Loop Until j = 3
    
    ' If there are one more Image - Load it
    If i < Len(buf) Then
        fNum = FreeFile
        Open "temp.gif" For Binary As fNum
            picbuf = String(Len(fileHeader) + Len(buf) - i, Chr(0))
            picbuf = fileHeader & Mid(buf, i - 1, Len(buf) - i)
            Put #fNum, 1, picbuf
            imgHeader = Left(Mid(buf, i - 1, Len(buf) - i), 16)
        Close fNum
        TimeWait = ((Asc(Mid(imgHeader, 4, 1))) + (Asc(Mid(imgHeader, 5, 1)) * 256)) * 10
        If imgCount > 1 Then
            FrameX = Asc(Mid(imgHeader, 9, 1)) + (Asc(Mid(imgHeader, 10, 1)) * 256)
            FrameY = Asc(Mid(imgHeader, 11, 1)) + (Asc(Mid(imgHeader, 12, 1)) * 256)
            Load aImg(imgCount - 1)
            aImg(imgCount - 1).Left = FrameX '* Screen.TwipsPerPixelX
            aImg(imgCount - 1).Top = FrameY '* Screen.TwipsPerPixelY
        End If
        aImg(imgCount - 1).Tag = TimeWait
        aImg(imgCount - 1).Picture = LoadPicture("temp.gif")
        ReDim Preserve Dispose(aImg.Count - 1)
        Dispose(aImg.Count - 1).Disposed = Asc(Mid(imgHeader, 3, 1)) / 4 And 3
        Dispose(aImg.Count - 1).FrameXPos = FrameX
        Dispose(aImg.Count - 1).FrameYPos = FrameY
        Kill ("temp.gif")
    End If
    TotalFrames = aImg.Count - 1
    LoadGif = True
    If aImg.Count >= 2 Then
        Load aImg(aImg.Count)
        aImg(aImg.Count - 1).Width = aImg(0).Width
        aImg(aImg.Count - 1).Height = aImg(0).Height
        For i = 1 To aImg.Count - 2
            If Dispose(i).Disposed = 0 Then
                'nothing
            ElseIf Dispose(i).Disposed = 1 Then
                'previous frame + actual frame(transparent) = result frame
                aImg(aImg.Count - 1).Picture = aImg(i - 1).Image
                Debug.Print TransparentBlt(aImg(aImg.Count - 1).hdc, Dispose(i).FrameXPos, Dispose(i).FrameYPos, aImg(i).ScaleWidth, aImg(i).ScaleHeight, aImg(i).hdc, 0, 0, aImg(i).ScaleWidth, aImg(i).ScaleHeight, GetPixel(aImg(i).hdc, 0, 0))
                aImg(i).Picture = aImg(aImg.Count - 1).Image
                aImg(i).Left = 0 'FrameX * Screen.TwipsPerPixelX
                aImg(i).Top = 0 'FrameY * Screen.TwipsPerPixelY
                aImg(aImg.Count - 1).Cls
            End If
        Next i
        Unload aImg(aImg.Count - 1)
    End If
    LoadGif = True
    Exit Function
ErrHandler:
 MsgBox "Error No. " & Err.Number & " when reading file", vbCritical
 LoadGif = False
 On Error GoTo 0
End Function

[jmsrickland]

OK, here is another BAS module

BTW: You are not using the correct value for the background color

      +------+----+----+--+--+--+-----------------------
      |GIF89a|1400|1900|F7|04|00|<--- Start of GCT --->
      +------+----+----+--+--+--+-----------------------
                        |  |
    If high bit is 1 ---+  |
    then use this byte ----+
    as index into Global 
    Color Table for the 
    background color

[joaquim]

OK, here is another BAS module

BTW: You are not using the correct value for the background color

      +------+----+----+--+--+--+-----------------------
      |GIF89a|1400|1900|F7|04|00|<--- Start of GCT --->
      +------+----+----+--+--+--+-----------------------
                        |  |
    If high bit is 1 ---+  |
    then use this byte ----+
    as index into Global 
    Color Table for the 
    background color

i see 1 error that sometimes i do... instead start with '1', i start with '0'. the 1st byte is '1' and not '0'
i need ask 2 things:
1 - all bytes are in hexadecimal values?
2 - if so. when we see the Logical Screen Descriptor(for sample) the Packed Field(2 bytes). we need convert it to binary and then catch the bits that we need, right? or theres another calculation\formula more easy?

[jmsrickland]

'There is no error you just need to know how to read the bits of the bytes

The Format Is this:

Bit Position  = 7 6 5 4 3 2 1 0
          F7  = 1 1 1 1 0 1 1 1

You can see that the high bit is set to 1
                                        |
                                        |
                                        1 1 1 1  0 1 1 1
                                           F        7

Which means you use the next byte 04 an the index into the Global Color Table. The 04 does not mean to use the 5th byte as the color. It means you need to multiply the index by 3 and add that value the the base address of the color table

The table has 3-bytes per color, like this:

  <--------------- Global Color Table (up to 768 Bytes) -------------------->
  Color 0    Color 1    Color 2    Color 3    Color 4                Color 254  Color 255
| 00 00 00 | 80 00 00 | 00 80 00 | 80 80 00 | XX XX XX | ......... | 00 FF FF | FF FF FF |

Keep in mind that there may not even be a Global Color Table. If this is the case then all
frames use their own Local Color Table if they have one.

Also, even if there is a Global Color Table it may or may not be used.

[jmsrickland]

i see 1 error that sometimes i do... instead start with '1', i start with '0'. the 1st byte is '1' and not '0'
i need ask 2 things:
1 - all bytes are in hexadecimal values?
2 - if so. when we see the Logical Screen Descriptor(for sample) the Packed Field(2 bytes). we need convert it to binary and then catch the bits that we need, right? or theres another calculation\formula more easy?

What 2-byte packed field are you referring to? A packed field is only 1-byte

You don't convert to binary, you convert to Ascii. For example, if you want to test the Global Color Table bit (in the above example it is the byte that has the &HF7 = 11110111 ) you AND that byte with 128(= &H80 = 10000000) and if it equals 128 then the bit is set on and that means there is a Global Color Table

In VB you would do it this way:

If Asc(Mid(GifBuffer, 11, 1)) And 128 = 128 Then
  '
  ' Here if there is a Global Color Table
  '
End If

[joaquim]

What 2-byte packed field are you referring to? A packed field is only 1-byte

You don't convert to binary, you convert to Ascii. For example, if you want to test the Global Color Table bit (in the above example it is the byte that has the &HF7 = 11110111 ) you AND that byte with 128(= &H80 = 10000000) and if it equals 128 then the bit is set on and that means there is a Global Color Table

In VB you would do it this way:

If Asc(Mid(GifBuffer, 11, 1)) And 128 = 128 Then
  '
  ' Here if there is a Global Color Table
  '
End If

Logical Screen Descriptor -> Packed Byte i see '91', then it's 2 digits are 1 byte.. after see your nice table... thanks.
you give me for Global Color Table, but i still don't understand for others values
can you give me the formula?

[jmsrickland]

                                      +---- GIF Header ---+
                                      |                   |
 Packed byte -------------------------|--------------+    | 
 Logical Screen Height ---------------|------------+ |    |
 Logical Screen Width ----------------|---------+  | |    |
                                      |         |  | |    |
                                      +---+---+--+--+-+-+-+
                                      |GIF|89a|  |  | | | |
                                      +---+---+--+--+-+-+-+    
                                                     | | | 
                                                     | | + -- Pixel Aspect Ratio 
                                                     | + ---- Background Color Index
                                                     |
 Global Color Table Size ----------------------+     |
 Sort Flag --------------------------------+   |     |
 Color Resolution ---------------------+   |   |     |
 Global Color Table Flag ----------+   |   |   |     |
                                   |   |   |   |     |
                                   |   |   |   |     |
                                   7 6 5 4 3 2 1 0   |                                              
                                  +-+-----+-+-----+  |                                                              
                                  | |     | |     | -+
                                  +-+-----+-+-----+
                                   |       |
                                   |       + --- 0 Table not sorted
                                   |             1 Table is sorted decreasing importance, most important color first.
                                   |
                                   + 
                                   1 = Global Color Table - Use next byte as index for Background Color
                                   0 = No Global Color Table - Next byte is meaningless                                     

  Size of Global Color Table       3 * (2 ^ ((Value of bits 2 1 0) + 1))

You say you are looking at a 91. Now is that a Decimal 91 (same as Ascii) or is it &H91?

Assuming it is &H91 then you have this:

91 = 1000 0001

Now look at above table I posted and you can see that the high bit is on so therefore you have a Global Color Table and because the last three bit are 001 that says you color table is only 1 which doesn't make sense.

Now if it is Ascii 91 then that means it is &H5B and 5B = 0101 1011

And that says the high bit is off so there is no Global Color Table

Which GIF file are you looking at?

[joaquim]

                                      +---- GIF Header ---+
                                      |                   |
 Packed byte -------------------------|--------------+    | 
 Logical Screen Height ---------------|------------+ |    |
 Logical Screen Width ----------------|---------+  | |    |
                                      |         |  | |    |
                                      +---+---+--+--+-+-+-+
                                      |GIF|89a|  |  | | | |
                                      +---+---+--+--+-+-+-+    
                                                     | | | 
                                                     | | + -- Pixel Aspect Ratio 
                                                     | + ---- Background Color Index
                                                     |
 Global Color Table Size ----------------------+     |
 Sort Flag --------------------------------+   |     |
 Color Resolution ---------------------+   |   |     |
 Global Color Table Flag ----------+   |   |   |     |
                                   |   |   |   |     |
                                   |   |   |   |     |
                                   7 6 5 4 3 2 1 0   |                                              
                                  +-+-----+-+-----+  |                                                              
                                  | |     | |     | -+
                                  +-+-----+-+-----+
                                   |       |
                                   |       + --- 0 Table not sorted
                                   |             1 Table is sorted decreasing importance, most important color first.
                                   |
                                   + 
                                   1 = Global Color Table - Use next byte as index for Background Color
                                   0 = No Global Color Table - Next byte is meaningless                                     

  Size of Global Color Table       3 * (2 ^ ((Value of bits 2 1 0) + 1))

You say you are looking at a 91. Now is that a Decimal 91 (same as Ascii) or is it &H91?

Assuming it is &H91 then you have this:

91 = 1000 0001

Now look at above table I posted and you can see that the high bit is on so therefore you have a Global Color Table and because the last three bit are 001 that says you color table is only 1 which doesn't make sense.

Now if it is Ascii 91 then that means it is &H5B and 5B = 0101 1011

And that says the high bit is off so there is no Global Color Table

Which GIF file are you looking at?

so you did:

asc(91)=5B
then you convert 5B(hexadecimal) to binary that is 0101 1011.
now we need the last 3 digits: 011
3 * (2 ^ ((011) + 1))=12288
"Which GIF file are you looking at?"
what i'm trying to do is learn how read the bits

[jmsrickland]

You are not paying attention to what I am saying to you.

First: Asc(91) does not equal 5B. It the other way around; Asc(Chr(&H5B)) = 91. To get the hexadecimal you simply do this Hex(91) = 5B

If it is decimal 91 (which means the byte is 5B then there is no Global Color Table so it is meaningless to try and to find it's size.

Second, you do not use the last 3-bits like you are doing. Do not do this:

3 * (2 ^ ((011) + 1))=12288

because you are using the last 3-bits as the value and that is not what you should do. 011 = 3 so you math would be this:

3 * (2 ^ 3) + 1 = 25

Your VB code for this is this:

3 * (2 ^ (Asc(Mid(GifBuffer, 11, 1)) And 3)) + 1

But remember, &H5B says there is no global color table which means that the frame(s) have their own

[jmsrickland]

You are not paying attention to what I am saying to you.

First: Asc(91) does not equal 5B. It the other way around; Asc(Chr(&H5B)) = 91. To get the hexadecimal you simply do this Hex(91) = 5B

If it is decimal 91 (which means the byte is 5B then there is no Global Color Table so it is meaningless to try and to find it's size.

Second, you do not use the last 3-bits like you are doing. Do not do this:

3 * (2 ^ ((011) + 1))=12288

because you are using the last 3-bits as the value and that is not what you should do. 011 = 3 so you math would be this:

3 * (2 ^ 3) + 1 = 25

3 * (2 ^ (Asc(Mid(buf, 11, 1)) And 3)) + 1

But remember, &H5B says there is no global color table which means that the frame(s) have their own

[joaquim]

You are not paying attention to what I am saying to you.

First: Asc(91) does not equal 5B. It the other way around; Asc(Chr(&H5B)) = 91. To get the hexadecimal you simply do this Hex(91) = 5B

If it is decimal 91 (which means the byte is 5B then there is no Global Color Table so it is meaningless to try and to find it's size.

Second, you do not use the last 3-bits like you are doing. Do not do this:

3 * (2 ^ ((011) + 1))=12288

because you are using the last 3-bits as the value and that is not what you should do. 011 = 3 so you math would be this:

3 * (2 ^ 3) + 1 = 25

But remember, &H5B says there is no global color table which means that the frame(s) have their own

ok... thanks for correct me.
i know that 011(binary)=3(decimal). the vb6 have something for convert the binary to decimal or i must build a function?
"But remember, &H5B says there is no global color table which means that the frame(s) have their own"
it's a const value?

[jmsrickland]

You are not paying attention to what I am saying to you.

First: Asc(91) does not equal 5B. It the other way around; Asc(Chr(&H5B)) = 91. To get the hexadecimal you simply do this Hex(91) = 5B

If it is decimal 91 (which means the byte is 5B then there is no Global Color Table so it is meaningless to try and to find it's size.

Second, you do not use the last 3-bits like you are doing. Do not do this:

3 * (2 ^ ((011) + 1))=12288

because you are using the last 3-bits as the value and that is not what you should do. 011 = 3 so you math would be this:

3 * (2 ^ 3) + 1 = 25

Your VB code is this:

3 * (2 ^ (Asc(Mid(GifBuffer, 11, 1)) And 3)) + 1

But remember, &H5B says there is no global color table which means that the frame(s) have their own so the above calculation would be meaningless in this case but you would use this when there is a global color table or use it for a local color table except the offset 11 would be a different number

3 * (2 ^ (Asc(Mid(GifBuffer, ??, 1)) And 3)) + 1

where ?? is the string position for the byte that is used for a local color table

To extract the values from this byte use the following

7654 3210
xxxx xxxx

And 128 to get x000 0000 = Global Color Table Flag
And 48 to get 0xxx 0000 = Color Resolution
And 8 to get 0000 x000 = Sort Flag
And 3 to get 0000 0xxx = Global Color Table Size

[joaquim]

"3 * (2 ^ (Asc(Mid(GifBuffer, 11, 1)) And 3)) + 1"
then it's:
3 * (2 ^ (Asc(Mid(GifBuffer, 11, 1)) And BinaryConvertedToDecimal)) + 1
right?

[joaquim]

You are not paying attention to what I am saying to you.

First: Asc(91) does not equal 5B. It the other way around; Asc(Chr(&H5B)) = 91. To get the hexadecimal you simply do this Hex(91) = 5B

If it is decimal 91 (which means the byte is 5B then there is no Global Color Table so it is meaningless to try and to find it's size.

Second, you do not use the last 3-bits like you are doing. Do not do this:

3 * (2 ^ ((011) + 1))=12288

because you are using the last 3-bits as the value and that is not what you should do. 011 = 3 so you math would be this:

3 * (2 ^ 3) + 1 = 25

Your VB code is this:

3 * (2 ^ (Asc(Mid(GifBuffer, 11, 1)) And 3)) + 1

But remember, &H5B says there is no global color table which means that the frame(s) have their own so the above calculation would be meaningless in this case but you would use this when there is a global color table or use it for a local color table except the offset 11 would be a different number

3 * (2 ^ (Asc(Mid(GifBuffer, ??, 1)) And 3)) + 1

where ?? is the string position for the byte that is used for a local color table

To extract the values from this byte use the following

7654 3210
xxxx xxxx

And 128 to get x000 0000
And 48 to get 0xxx 0000
And 8 to get 0000 x000
And 3 to get 0000 0111

3 * (2 ^ (Asc(Mid(GifBuffer, 11, 1)) And 8)) + 1
and i have the short flag
i understand, but i still have the question: but the Graphics Control Extension - > Packed Field have a diferent configuraction, right?

[jmsrickland]

The calculation 3 * (2 ^ (Asc(Mid(GifBuffer, 11, 1)) And 3)) + 1 is for the color table size only, not the other fields.

Global Color Table Flag = Asc(Mid(GifBuffer, 11, 1)) And 128
Color Resolution = Asc(Mid(GifBuffer, 11, 1)) And 48
Sort Flag = Asc(Mid(GifBuffer, 11, 1)) And 8
Global Color Table Size = 3 * (2 ^ (Asc(Mid(GifBuffer, 11, 1)) And 3)) + 1

[jmsrickland]

3 * (2 ^ (Asc(Mid(GifBuffer, 11, 1)) And 8)) + 1
and i have the short flag
i understand, but i still have the question: but the Graphics Control Extension - > Packed Field have a diferent configuraction, right?

Yes

It is this:

       
                                  End of 
                                  GCE Data
                 4 Bytes of          |
                  GCE Data           |                    
                   |                 |                          
        GCE        | Byte:           |  
        Indicator  |    X1 X2 X3 X4  |     
             |     |    |  |  |  |   |    
         | 21 F9 | 04 | 05 32 00 09 00

[jmsrickland]

Here is a complete description of the GCE

"Extension Introducer"
Identifies beginning          
of an extension Block ----------+                            Block Terminator
                                |                                  |
                                |                                  |
                              +----+----+----+----+----+----+----+----+       
                              | 21 | F9 | 04 | X1 | X2 | X3 | X4 | 00 |
                              +----+----+----+----+----+----+----+----+ 
                                     |    |  |                   |
                                     |    |  |<- Control Block ->|
Graphic Control Label ---------------+    |
                                          +---- Block Size (Fixed Value)


            block. This field contains the fixed value 0x21.

            ii) Graphic Control Label - Identifies the current block as a
            Graphic Control Extension. This field contains the fixed value
            0xF9.

            iii) Block Size - Number of bytes in the block, after the Block
            Size field and up to but not including the Block Terminator.  This
            field contains the fixed value 4.

            iv) Disposal Method - Indicates the way in which the graphic is to
            be treated after being displayed.
             |    
             +-----------------------+
                                     |
                              +----+----+----+----+----+
                              | 04 | X1 | X2 | X3 | X4 |
                              +----+----+----+----+----+
                                     |
                        +------------+
                        |
                        |
                        ---------------
                   X1 = 7 6 5 4 3 2 1 0
                        ---------------
                        x x x x 0 0 x x   
                        x x x x 0 1 x x   
                        x x x x 1 0 x x   
                        x x x x 1 1 x x   
                                 |                            
                                 |                            
                       +---------+     
                       |                         
                       00   0  No disposal specified 
                       01   1  Do not dispose - Leave
                       10   2  Restore Background
                       11   3  Restore Previous

                       Bits 7 6 5 3 To be defined 

            v) User Input Flag - Indicates whether or not user input is
            expected before continuing. If the flag is set, processing will
            continue when user input is entered. The nature of the User input
            is determined by the application (Carriage Return, Mouse Button
            Click, etc.).
             |    
             +------------------------+ 
                                      |
                  X1 =    7 6 5 4 3 2 1 0
                          ---------------
                          x x x x d d 0 x 
                          x x x x d d 1 x 

            Values :    0 -   User input is not expected.
                        1 -   User input is expected.

            When a Delay Time is used and the User Input Flag is set,
            processing will continue when user input is received or when the
            delay time expires, whichever occurs first.


            vi) Transparency Flag - Indicates whether a transparency index is
            given in the Transparent Index field. (This field is the least
            significant bit of the byte.)
             |    
             +--------------------------+ 
                                        |
                  X1 =    7 6 5 4 3 2 1 0
                          ---------------
                          x x x x x x x 0
                          x x x x d d u 1   

            Values :    0 -   Transparent Index is not given.
                        1 -   Transparent Index is given.


            vii) Delay Time - If not 0, this field specifies the number of
            hundredths (1/100) of a second to wait before continuing with the
            processing of the Data Stream. The clock starts ticking immediately
            after the graphic is rendered. This field may be used in
            conjunction with the User Input Flag field.
             |    
             +----------------------------+----+  2-byte value 
                                          |    |
                     +---+----+----+----+----+----+----+----+
                     |21 | F9 | 04 | X1 | X2 | X3 | X4 | 00 |
                     +---+----+----+----+----+----+----+----+

            viii) Transparency Index - The Transparency Index is such that when
            encountered, the corresponding pixel of the display device is not
            modified and processing goes on to the next pixel. The index is
            present if and only if the Transparency Flag is set to 1.
             |    
             +--------------------------------------+
                                                    |
                     +---+----+----+----+----+----+----+----+
                     |21 | F9 | 04 | X1 | X2 | X3 | X4 | 00 |
                     +---+----+----+----+----+----+----+----+


            ix) Block Terminator - This [1 byte] zero-length data block marks the end of the 
             |                     Graphic Control Extension.
             |    
             +-------------------------------------------+
                                                         |
                     +---+----+----+----+----+----+----+----+
                     |21 | F9 | 04 | X1 | X2 | X3 | X4 | 00 |
                     +---+----+----+----+----+----+----+----+