C / C++ / MFC

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

int dst_width = <width>
int dst_height = <height>
CBitmap src_bitmap; // this should already exist
CBitmap dst_bitmap; // we'll create this one
// get source bitmap dimensions
BITMAP src_info;
src_bitmap.GetBitmap(&src_info);
// create memory device contexts and destination bitmap
CDC src_DC,dst_DC,screen_DC;
screen_DC.Attach(::GetDC(NULL));
dst_bitmap.CreateCompatibleBitmap(&screen_DC,dst_width,dst_height);
src_DC.CreateCompatibleDC(NULL);
dst_DC.CreateCompatibleDC(NULL);
dst_DC.SetStretchBltMode(HALFTONE); // you may or may not want to do this
// perform StretchBlt from source to destination (copies image)
CBitmap *src_previous = src_DC.SelectObject(&src_bitmap);
CBitmap *dst_previous = dst_DC.SelectObject(&dst_bitmap);
dst_DC.StretchBlt(0,0,dst_width,dst_height,
                  &src_DC,0,0,src_info.bmWidth,src_info.bmHeight,
                  SRCCOPY);
// cleanup
src_DC.SelectObject(src_previous);
dst_DC.SelectObject(dst_previous);
// at this point, dst_bitmap contains your resized bitmap

void CLabeledBitmap::CopyBitmapSection(CBitmap &bmpSrc, CBitmap &bmpDest, CRect &rectSection, CDC* pDC)
{
    int nWidth = rectSection.Width();
    int nHeight = rectSection.Height();
 	
    CDC destDC, srcDC;
 	
    CBitmap *pOldBmp = NULL;
    CBitmap *pOldSrcBmp = NULL;
 
    // Create two device contexts, one for the destination bitmap and one for the source bitmap.
    destDC.CreateCompatibleDC(pDC);
    srcDC.CreateCompatibleDC(pDC);
 
    // Make sure that the destination bitmap is empty.
    bmpDest.DeleteObject();

    // Create a bitmap that is compatible with the current device context.
    bmpDest.CreateCompatibleBitmap(pDC, nWidth, nHeight);
 
    // Select the bitmaps into the device contexts.
    pOldSrcBmp = srcDC.SelectObject(&bmpSrc);
    pOldBmp = destDC.SelectObject(&bmpDest);
 
    // Transfer the section of the source bitmap into the destination bitmap.
    destDC.StretchBlt(0, 0, nWidth, nHeight, &srcDC, rectSection.left, rectSection.top,
                      rectSection.Width(), rectSection.Height(), SRCCOPY);
 
    // Set the dimensions of the bitmap so that they can be used later.
    // Otherwise, they will be invalid.
    bmpDest.SetBitmapDimension(nWidth, nHeight);
 
    // Clean up the device contexts.
    destDC.SelectObject(pOldBmp);
    srcDC.SelectObject(pOldSrcBmp);
}