BitMap to Bytes - An Attempt

Hi!

A lot of times it has been asked, yours truly inlcuded, how a Bitmap in an app can be serialized into a byte array. Given below is an attempt modifying an example from All-API Guide. Hope this provides a start to all of you. The array is now written to disk. But can be sent directly through Winsock for network tranfer.

VB Code:

'The Sending App, containing a PictureBox and a Command Button
'ScaleMode of the Form and the PictureBox set to Pixels
 
Private Const BI_RGB = 0&
Private Const DIB_RGB_COLORS = 0
Private Type BITMAPINFOHEADER
        biSize As Long
        biWidth As Long
        biHeight As Long
        biPlanes As Integer
        biBitCount As Integer
        biCompression As Long
        biSizeImage As Long
        biXPelsPerMeter As Long
        biYPelsPerMeter As Long
        biClrUsed As Long
        biClrImportant As Long
End Type
Private Type RGBQUAD
        rgbBlue As Byte
        rgbGreen As Byte
        rgbRed As Byte
        rgbReserved As Byte
End Type
Private Type BITMAPINFO
        bmiHeader As BITMAPINFOHEADER
        bmiColors As RGBQUAD
End Type
Private Declare Function CreateCompatibleDC Lib "gdi32" _
(ByVal hdc As Long) As Long
Private Declare Function CreateDIBSection Lib "gdi32" _
(ByVal hdc As Long, pBitmapInfo As BITMAPINFO, _
ByVal un As Long, ByVal lplpVoid As Long, _
ByVal handle As Long, ByVal dw As Long) As Long
Private Declare Function GetDIBits Lib "gdi32" _
(ByVal aHDC As Long, ByVal hBitmap As Long, ByVal nStartScan _
As Long, ByVal nNumScans As Long, lpBits As Any, _
lpBI As BITMAPINFO, ByVal wUsage As Long) As Long
Private Declare Function SelectObject Lib "gdi32" _
(ByVal hdc As Long, ByVal hObject As Long) As Long
Private Declare Function DeleteDC Lib "gdi32" _
(ByVal hdc As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" _
(ByVal hObject As Long) As Long
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 GetDC Lib "user32" _
(ByVal hwnd As Long) As Long
Dim iBitmap As Long, iDC As Long
 
Private Sub Command1_Click()
    Dim bi24BitInfo As BITMAPINFO, bBytes() As Byte
    With bi24BitInfo.bmiHeader
        .biBitCount = 24
        .biCompression = BI_RGB
        .biPlanes = 1
        .biSize = Len(bi24BitInfo.bmiHeader)
        .biWidth = Picture1.Width
        .biHeight = Picture1.Height
    End With
    ReDim bBytes(1 To bi24BitInfo.bmiHeader.biWidth * _
    bi24BitInfo.bmiHeader.biHeight * 3) As Byte
 
    iDC = CreateCompatibleDC(0)
 
    iBitmap = CreateDIBSection(iDC, bi24BitInfo, _
    DIB_RGB_COLORS, ByVal 0&, ByVal 0&, ByVal 0&)
 
    SelectObject iDC, iBitmap
 
    BitBlt iDC, 0, 0, bi24BitInfo.bmiHeader.biWidth, _
    bi24BitInfo.bmiHeader.biHeight, Picture1.hdc, 0, 0, _
    vbSrcCopy
 
    GetDIBits iDC, iBitmap, 0, _
    bi24BitInfo.bmiHeader.biHeight, bBytes(1), _
    bi24BitInfo, DIB_RGB_COLORS
 
        Open App.Path & "\CloudsCopy.BMP" For Binary As #1
            Put #1, 1, CLng(Picture1.Width)
            Put #1, 5, CLng(Picture1.Height)
            Put #1, 9, bBytes
        Close #1
    DeleteDC iDC
    DeleteObject iBitmap
    Client.Show 'Run the client App. I used two forms in the same app
End Sub
 
Private Sub Form_Load()
Me.ScaleMode = vbPixels
With Picture1
    .ScaleMode = vbPixels
    .AutoRedraw = True
    .AutoSize = True
    .Picture = LoadPicture(App.Path & "\Clouds.bmp")
End With
End Sub
 
'The recieving App containing a pictureBox with a command button
'with the form and picturebox scalemode set to Pixels and
'autoredraw, autosize of the pictureBox set to true
 
Private Declare Function SetDIBitsToDevice Lib "gdi32" _
(ByVal hdc As Long, ByVal x As Long, ByVal y As Long, _
ByVal dx As Long, ByVal dy As Long, ByVal SrcX As Long, _
ByVal SrcY As Long, ByVal Scan As Long, ByVal NumScans _
As Long, Bits As Any, BitsInfo As BITMAPINFO, ByVal wUsage _
As Long) As Long
Private Const BI_RGB = 0&
Private Const DIB_RGB_COLORS = 0
Private Type BITMAPINFOHEADER
        biSize As Long
        biWidth As Long
        biHeight As Long
        biPlanes As Integer
        biBitCount As Integer
        biCompression As Long
        biSizeImage As Long
        biXPelsPerMeter As Long
        biYPelsPerMeter As Long
        biClrUsed As Long
        biClrImportant As Long
End Type
Private Type RGBQUAD
        rgbBlue As Byte
        rgbGreen As Byte
        rgbRed As Byte
        rgbReserved As Byte
End Type
Private Type BITMAPINFO
        bmiHeader As BITMAPINFOHEADER
        bmiColors As RGBQUAD
End Type
 
Private Sub Command1_Click()
Dim bi24BitInfo As BITMAPINFO, bmpWidth As Long, _
bmpHeight As Long
Dim bbBytes() As Byte
Open App.Path & "\CloudsCopy.BMP" For Binary As #1
    ReDim bbBytes(1 To (LOF(1) - 8))
        Get #1, 1, bmpWidth
        Get #1, 5, bmpHeight
        Get #1, 9, bbBytes
Close #1
 
    With bi24BitInfo.bmiHeader
        .biBitCount = 24
        .biCompression = BI_RGB
        .biPlanes = 1
        .biSize = Len(bi24BitInfo.bmiHeader)
        .biWidth = bmpWidth
        .biHeight = bmpHeight
    End With
        Picture1.Width = bmpWidth
        Picture1.Height = bmpHeight
    
    SetDIBitsToDevice Picture1.hdc, 0, 0, _
    bi24BitInfo.bmiHeader.biWidth, _
    bi24BitInfo.bmiHeader.biHeight, 0, 0, 0, _
    bi24BitInfo.bmiHeader.biHeight, bbBytes(1), _
    bi24BitInfo, DIB_RGB_COLORS
    
    Picture1.AutoSize = True
    Picture1.Refresh
End Sub
 
Private Sub Form_Load()
Me.ScaleMode = vbPixels
Picture1.ScaleMode = vbPixels
End Sub

you can convert a bitmap to a byte array with the GetBitmapBits API


Add a picturebox with a picture in it, and a command button

VB Code:

Private Declare Function GetBitmapBits Lib "gdi32" (ByVal hBitmap As Long, ByVal dwCount As Long, lpBits As Any) As Long
Private Declare Function SetBitmapBits Lib "gdi32" (ByVal hBitmap As Long, ByVal dwCount As Long, lpBits As Any) As Long
Private Declare Function GetObject Lib "gdi32" Alias "GetObjectA" (ByVal hObject As Long, ByVal nCount As Long, lpObject As Any) As Long
Private Type BITMAP
    bmType As Long
    bmWidth As Long
    bmHeight As Long
    bmWidthBytes As Long
    bmPlanes As Integer
    bmBitsPixel As Integer
    bmBits As Long
 
End Type
 
Private Sub Command1_Click()
    Dim hbm As Long
    Dim bm As BITMAP
    Dim status As Long
    Dim bytes() As Byte
    Dim i As Long
    Dim j As Long
    Dim wid As Long
    Dim hgt As Long
    
    hbm = Picture1.Image
    
    '-- Get status of bitmap
    status = GetObject(hbm, Len(bm), bm)
    
    '-- Get the Bits
    wid = bm.bmWidthBytes
    hgt = bm.bmHeight
    ReDim bytes(1 To wid, 1 To hgt)
    
    status = GetBitmapBits(hbm, wid * hgt, bytes(1, 1))
    '-- We now have the entire bitmap in our Byte Array
    
    
    '-- And if you want to modify the image ( makes it darker )
    For i = 1 To wid
        For j = 1 To hgt
            bytes(i, j) = bytes(i, j) / 2
        Next j
    Next i
    
    '-- Set the Bits
    status = SetBitmapBits(hbm, wid * hgt, bytes(1, 1))
    
    
End Sub

Thanks for that :)

I tried the following

VB Code:

'First App
Picture1.Picture = LoadPicture(App.Path & "\Clouds.bmp")
    Dim hbm As Long
    Dim bm As BITMAP
    Dim status As Long
    Dim bytes() As Byte
    Dim i As Long
    Dim j As Long
    Dim wid As Long
    Dim hgt As Long
    
    hbm = Picture1.Image
    
    '-- Get status of bitmap
    status = GetObject(hbm, Len(bm), bm)
    
    '-- Get the Bits
    wid = bm.bmWidthBytes
    hgt = bm.bmHeight
    ReDim bytes(1 To wid, 1 To hgt)
    
   status = GetBitmapBits(hbm, wid * hgt, bytes(1, 1))
    '-- We now have the entire bitmap in our Byte Array
    
     Open App.Path & "\CloudsCopy.BMP" For Binary As #1
            Put #1, 1, CLng(wid)
            Put #1, 5, CLng(hgt)
            Put #1, 9, bytes
    Close #1
    Client.Show
    
'Second App
Private Sub Command1_Click()
Dim bmpWidth As Long, bmpHeight As Long
Dim bbBytes() As Byte
Dim hbm As Long
hbm = Picture1.Image
Open App.Path & "\CloudsCopy.BMP" For Binary As #1
        Get #1, 1, bmpWidth
        Get #1, 5, bmpHeight
Close #1
Open App.Path & "\CloudsCopy.BMP" For Binary As #1
    ReDim bbBytes(1 To bmpWidth, 1 To bmpHeight)
        Get #1, 9, bbBytes
Close #1
 
status = SetBitmapBits(hbm, bmpWidth * bmpHeight, bbBytes(1, 1))
Picture1.AutoSize = True
Picture1.Refresh

I get just a series of white, green and blue horizontal lines in the second form/app :confused: :confused:

Where am I wrong?

Thanks

hmmm thats interesting, the image gets badly distorted
yet the file contents matches the byte array

I made the byte array to a single dimensional array ( redim bytes(1 to wid*hgt) ) thinking that could be the problem, yet it still distorts

Ive tried removing the width and height ( 8 bytes ) from the start of the file and loading it, still distorts

Ive done a comparison between the file data and the bytes, and its exactly the same

im stumped

Will try some more :) :) and keep you posted

Ta

API Guide to the rescue again!:D
The dimensioning of the array is like so. So says an example from the ALL API Guide.

VB Code:

BytesPerLine = (PicInfo.bmWidth * 3 + 3) And &HFFFFFFFC
    ReDim PicBits(1 To BytesPerLine * PicInfo.bmHeight * 3) As Byte

This one works ok for me.

VB Code:

'Form One
Dim PicBits() As Byte, PicInfo As BITMAP
Dim BytesPerLine As Long
Picture1.Picture = LoadPicture(App.Path & "\Clouds.bmp")
    GetObject Picture1.Image, Len(PicInfo), PicInfo
    BytesPerLine = (PicInfo.bmWidth * 3 + 3) And &HFFFFFFFC
    ReDim PicBits(1 To BytesPerLine * PicInfo.bmHeight * 3) As Byte
    GetBitmapBits Picture1.Image, UBound(PicBits), PicBits(1)
 
     Open App.Path & "\CloudsCopy.BMP" For Binary As #1
            Put #1, 1, CLng(Picture1.Width)
            Put #1, 5, CLng(Picture1.Height)
            Put #1, 9, PicBits
    Close #1
    Client.Show
End Sub
 
'Client Form
Dim bmpWidth As Long, bmpHeight As Long, bbBytes() As Byte
Open App.Path & "\CloudsCopy.BMP" For Binary As #1
        Get #1, 1, bmpWidth
        Get #1, 5, bmpHeight
Close #1
Picture1.Width = bmpWidth
Picture1.Height = bmpHeight
Open App.Path & "\CloudsCopy.BMP" For Binary As #1
    ReDim bbBytes(1 To LOF(1) - 8)
        Get #1, 9, bbBytes
Close #1
SetBitmapBits Picture1.Image, UBound(bbBytes), bbBytes(1)
Picture1.Refresh

Looks all right?

Try this:

VB Code:

' Global Memory Flags
Const GMEM_MOVEABLE = &H2
Const GMEM_ZEROINIT = &H40
 
Const GHND = (GMEM_MOVEABLE Or GMEM_ZEROINIT)
 
Private Declare Function GlobalAlloc Lib "kernel32" ( _
  ByVal wFlags As Long, _
  ByVal dwBytes As Long) As Long
 
Private Declare Function GlobalSize Lib "kernel32" ( _
  ByVal hMem As Long) As Long
 
Private Declare Function GlobalLock Lib "kernel32" ( _
  ByVal hMem As Long) As Long
 
Private Declare Function GlobalUnlock Lib "kernel32" ( _
  ByVal hMem As Long) As Long
 
Const PictureID = &H746C&
 
Private Type PictureHeader
   Magic As Long
   Size As Long
End Type
 
Public Sub Picture2Array(ByVal oObj As StdPicture, aBytes() As Byte)
Dim oIPS As IPersistStream
Dim oStream As IStream
Dim hGlobal As Long
Dim lPtr As Long
Dim lSize As Long
Dim Hdr As PictureHeader
 
   ' Get the IPersistStream interface
   Set oIPS = oObj
   
   ' Create a IStream object
   ' on global memory
   Set oStream = CreateStreamOnHGlobal(0, True)
   
   ' Save the picture in the stream
   oIPS.Save oStream, True
      
   ' Get the global memory handle
   ' from the stream
   hGlobal = GetHGlobalFromStream(oStream)
   
   ' Get the memory size
   lSize = GlobalSize(hGlobal)
   
   ' Get a pointer to the memory
   lPtr = GlobalLock(hGlobal)
   
   If lPtr Then
   
      lSize = lSize - Len(Hdr)
      
      ' Redim the array
      ReDim aBytes(0 To lSize - 1)
   
      ' Copy the data to the array
      MoveMemory aBytes(0), ByVal lPtr + Len(Hdr), lSize
   
   End If
   
   ' Release the pointer
   GlobalUnlock hGlobal
   
   ' Release the IStream object
   Set oStream = Nothing
 
End Sub

cool :cool:

Thanx pal. That project's now over. But this is being added to my arsenal of VBForums Code Snippets.

Cheers and Good Luck :)