[RESOLVED] StretchDIBits Memory Leak??

[OrangeBlaze]

Hello all! I have code to retrieve a byte array from winsock and then I call StretchDIBits to take byte array into DC of my DIB section. I have never used StretchDIBits, only GetDIBits. After this, I BitBlt the DC onto Form1.

However, when I run the code, a big memory leak occurs! (up to 1.8 GB!!) I commented out StretchDIBits call and it did not leak.
Here is the code for Winsock_DataArrival

Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)

    Winsock1.GetData RecvBMP
    
    StretchDIBits BufferDC, 0, 0, Form1.ScaleWidth, Form1.ScaleHeight, 0, 0, 1280, 768, RecvBMP(6), bi24BitInfo, 0, vbSrcCopy
    
    'Draw buffer to form DC
    BitBlt Form1.hDC, 0, 0, Form1.ScaleWidth, Form1.ScaleHeight, BufferDC, 0, 0, vbSrcCopy

End Sub

Thanks in advance!!!

[VanGoghGaming]

Probably you need to switch the form's ScaleMode to pixels or otherwise convert twips to pixels before passing the values to "StretchDIBits".

Also you don't need a BufferDC, you could put it directly onto the form's hDC.

If the source and destination rectangles are wildly different, you can obtain a higher quality stretching with:

Private Declare Function SetStretchBltMode Lib "gdi32" (ByVal hDC As Long, ByVal nStretchMode As Long) As Long
Private Const HALFTONE As Long = 4

SetStretchBltMode Form1.hDC, HALFTONE

[VanGoghGaming]

You didn't provide more details about your "RecvBMP" array and what does it contain but since you seem to use a "bi24BitInfo" structure you need to add padding to the array's width if it's not a multiple of 4.

[OrangeBlaze]

Probably you need to switch the form's ScaleMode to pixels or otherwise convert twips to pixels before passing the values to "StretchDIBits".

Also you don't need a BufferDC, you could put it directly onto the form's hDC.

If the source and destination rectangles are wildly different, you can obtain a higher quality stretching with:

Private Declare Function SetStretchBltMode Lib "gdi32" (ByVal hDC As Long, ByVal nStretchMode As Long) As Long
Private Const HALFTONE As Long = 4

SetStretchBltMode Form1.hDC, HALFTONE

Thanks. I will check when I can but I believe I have set ScaleMode to pixels, and I know that I am passing ScaleWidth and ScaleHeight. What would I pass for BITMAPINFO parameter of StretchDIBits if I am placing it directly onto the form?

[OrangeBlaze]

You didn't provide more details about your "RecvBMP" array and what does it contain but since you seem to use a "bi24BitInfo" structure you need to add padding to the array's width if it's not a multiple of 4.

I think the problem may be in the padding.

Sender calls GetDIBits to put it into SendBMP. the first 6 bytes are 4 bytes for length descriptor, and 2 to indentify what kind of data it is. To make room for these, I put SendBMP(6) for lpBits parameter. GetDIBits seems to be fine. However, it is true that I think I padded array size, then added 6 to it AFTER the padding, so it was 2 bytes off.
I wonder if the missing 2 bytes in the array is what is causing StretchDIBits to leak? (even though I put RecvBMP(6) for the lpBits parameter)

[OrangeBlaze]

OK, I fixed the issue with 4 byte. It no longer leaks but now I have to make code for accounting that it does not all arrive in one piece. Will report back later if it works