[VB6] - About GetDIBits()

[joaquim]

i know that GetDIBits() converts RGB to BGR colors(it's how they work).
but for work with coordinates theres any diference??
or do i need convert them for compare them(using '+' or '-')?
i always do:

For Y = 0 To Height - 1
    For X = 0 To Width - 1
             '..........
    next X
next y

but i can use pixel(x+2, y+3) for compare the colors(converted to BGR) or i must convert the coordenates too?

[Mikle]

Function GetDIBits() and SetDIBitsToDevice() work with the parameter BITMAPINFOHEADER, Y coordinate is from bottom to top, to change it from top to bottom, you need to BITMAPINFOHEADER.biHeight write a negative number, for example:

  With bi32BitInfo.bmiHeader
    .biBitCount = 32
    .biPlanes = 1
    .biSize = Len(bi32BitInfo.bmiHeader)
    .biWidth = pic.ScaleWidth
    .biHeight = -pic.ScaleHeight
    .biSizeImage = 4 * pic.ScaleWidth * pic.ScaleHeight
  End With

To convert RGB to BGR, the coordinates do not need to change, that the transformation function RGB to BGR and BGR to RGB the same way:

Private Function SwapRGB(ByVal c As Long) As Long
  SwapRGB = (c And &HFF&) * &H10000 Or (c And &HFF00&) Or (c And &HFF0000) \ &H10000
End Function

i know that GetDIBits() converts RGB to BGR colors(it's how they work).

It is not, on the contrary, in VB6 color components are mixed for compatibility with older versions of BASIC, I recommend not to use functions RGB(), PSet(), Point() and constants, such vbRed, vbBlack ..., instead PSet() and Point() to use the SetPixel() and GetPixel().

[joaquim]

Function GetDIBits() and SetDIBitsToDevice() work with the parameter BITMAPINFOHEADER, Y coordinate is from bottom to top, to change it from top to bottom, you need to BITMAPINFOHEADER.biHeight write a negative number, for example:

  With bi32BitInfo.bmiHeader
    .biBitCount = 32
    .biPlanes = 1
    .biSize = Len(bi32BitInfo.bmiHeader)
    .biWidth = pic.ScaleWidth
    .biHeight = -pic.ScaleHeight
    .biSizeImage = 4 * pic.ScaleWidth * pic.ScaleHeight
  End With

To convert RGB to BGR, the coordinates do not need to change, that the transformation function RGB to BGR and BGR to RGB the same way:

Private Function SwapRGB(ByVal c As Long) As Long
  SwapRGB = (c And &HFF&) * &H10000 Or (c And &HFF00&) Or (c And &HFF0000) \ &H10000
End Function

It is not, on the contrary, in VB6 color components are mixed for compatibility with older versions of BASIC, I recommend not to use functions RGB(), PSet(), Point() and constants, such vbRed, vbBlack ..., instead PSet() and Point() to use the SetPixel() and GetPixel().

thanks

inWidth = Picture.ScaleWidth
    inHeight = Picture.ScaleHeight
    ReDim OriginalImage(inWidth - 1, inHeight - 1)
    With bi32BitInfo.bmiHeader
        .biBitCount = 32
        .biPlanes = 1
        .biSize = Len(bi32BitInfo.bmiHeader)
        .biWidth = inWidth
        .biHeight = inHeight
        .biSizeImage = 4 * inWidth * inHeight
    End With
   
    GetDIBits Picture.hdc, Picture.Image.Handle, 0, inHeight, OriginalImage(0, 0), bi32BitInfo, 0

like you see the size is, always positive. but someone tell me that DIB's works upside down. maybe is why my code is ignored or inverted on Y

[joaquim]

but if the Y is inverted, how can i work with it?

[Mikle]

I wrote:

Y coordinate is from bottom to top, to change it from top to bottom, you need to BITMAPINFOHEADER.biHeight write a negative number

Change

.biHeight = inHeight

to

.biHeight = -inHeight

[joaquim]

I wrote:

Change

.biHeight = inHeight

to

.biHeight = -inHeight

if i change that, i must change the way the image is drawed, right?

[Mikle]

You need change it for GetDiBits and for SetDiBitsToDevice simultaneously. Then you no longer need to change.

[joaquim]

ok... i know that i must change the StretchDIBits() for draw the image.
but i still having problems with Y
because TempY = Y + lngShadowY
and if lngShadowY >=0 the shadow is ignored
if i use it positive, the problem is inversed and the lngShadowY accept >=0 values correctly
and i don't understand why
can you advice me?

[joaquim]

SetDiBitsToDevice () is for draw it. but don't help me on Transparent and stretch draw

[Mikle]

Give me you working code where you have problem.

[joaquim]

sorry the late. didn't see it
heres how you use the class:

Dim GRP As Graphics
Private Sub Command1_Click()
    Set GRP = New Graphics
    Form1.Cls
    GRP.GetImageData Picture1 'get the image from a control
    GRP.ShadowColor = Picture6.BackColor
    GRP.ShadowX = Val(Text2.Text)
    GRP.ShadowY = Val(Text3.Text)
    GRP.DrawImage Form1 'draw the image on control
  
End Sub

on class you have the getimagedata() sub, changeimage() sub(here we do all effects). on changeimage() sub see the comments for catch the shadow effect.
the drawimage() sub is for draw the image and see how i do the mirror and tiles\stretch.

[joaquim]

after some tests i found these:
with: TempY = Y - lngShadowY
if ShadowY=0 then the ShadowX must be negative(don't make sence using the 0, in these sample);
if ShadowY>0 then ShadowX can be any number;
if ShadowY<0 then the shadow isn't showed. the values are ignored
can anyone advice me?

[Mikle]

You're in the loop will be overwritten by the new color previously drawn shadow. Replace in the Sub ChangeImage() the line:

    For Y = 0 To outHeight - 1

to fragment:

    Dim y_for As Long, y_to As Long, y_step As Long
    If lngShadowY > 0 Then
      y_for = outHeight - 1
      y_to = 0
      y_step = -1
    Else
      y_for = 0
      y_to = outHeight - 1
      y_step = 1
    End If
    For Y = y_for To y_to Step y_step

And for the cycle on X similarly.

[joaquim]

sorry, but the results are a black image(black color with image size)
see the class. if you want, give me your mail and i send you the entire project

[joaquim]

hehehe i put the shadow working hehehe
what i did?
well i create a second array for put the shadow image and other for it's mask(for do the transparency) and works fine. and for draw it i can choose the place, because, here, i don't use the Y coordenate
now i must complete my selection effect(is show 1 line arrow the image(image without backcolor).. like in games):

'Selection Color(needs more work)
            If lngSelectionWidth <> 0 And lngSelectionColor <> lngBackColor Then
                clrOldColor = RGBValues(lngBackColor)
                TempColor = RGB(clrOldColor.Blue, clrOldColor.Green, clrOldColor.Red)
                clrOldColor = RGBValues(lngSelectionColor)
                TempColor1 = RGB(clrOldColor.Blue, clrOldColor.Green, clrOldColor.Red)
                If (ChangedImage(X, Y) = TempColor And blnLeft = True) Then
                    For i = 1 To SelectionWidth
                        ChangedImage(X - i, Y) = TempColor1
                        MaskImage(X - i, Y) = vbBlack
                    Next i
                    
                    blnLeft = False
                ElseIf (ChangedImage(X, Y) <> TempColor And blnLeft = False) Then
                    For i = 1 To SelectionWidth
                        ChangedImage(X - i, Y) = TempColor1
                        MaskImage(X - i, Y) = vbBlack
                    Next i
                    blnLeft = True
                End If
            End If

these code works fine for X(left-right), but i don't know how can i put it working for Y(up-down).
any advices?

[joaquim]

now i understand why the shadow effects wasn't workin with some values: because without any data\pixel we can't compare values lol