Why does this code display the bitmap in memory only in 2 colors?

594610

Why does this code display the bitmap in memory only in 2 colors?
 void StrectBMP (char * fileSrc, HDC ClientDc, double proportion)
{
BITMAP srcInfo;
HBITMAP HBmpSource = (HBITMAP) LoadImage (0, fileSrc, IMAGE_BITMAP, 0,0, LR_LOADFROMFILE);
      
    HDC hsrc = CreateCompatibleDC (NULL);
HGDIOBJ hold = SelectObject (hsrc, HBmpSource);
GetObject (HBmpSource, sizeof (BITMAP), (LPVOID)&srcInfo);

HDC hDest = CreateCompatibleDC (NULL);
int mode = SetStretchBltMode (hDest, COLORONCOLOR);
// SelectStockObject (hDest, BLACK_BRUSH);
HBITMAP hmemBmp = CreateCompatibleBitmap (hDest, srcInfo.bmWidth,
                            srcInfo.bmHeight);
  HGDIOBJ holdsrc = SelectObject (hDest, hmemBmp);

BOOL b = StretchBlt (hDest, 0,0, srcInfo.bmWidth, srcInfo.bmHeight, hsrc, 0,0,
           srcInfo.bmWidth, srcInfo.bmHeight, SRCCOPY);

    b = BitBlt (ClientDc, 0,0, srcInfo.bmWidth, srcInfo.bmHeight, hDest, 0,0, SRCCOPY);
}

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ClientDc = GetDC (hWnd); // Window display area HDC
fileSrc is the bitmap file path.
Great help from everyone.

feng214

Change to
HBITMAP hmemBmp = CreateCompatibleBitmap (ClientDC, srcInfo.bmWidth,
                            srcInfo.bmHeight);

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Thank youfeng214. When my purpose is to reduce the bitmap in memory first and then get the bitmap data, BitBlt just wants to see the actual effect of memory mapping. I wonder if it can be implemented based on the above code?

594610

The problem has been resolved. Thank you all.