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Fixed fallback code for StretchBlt on RLE DIBs with gaps.

This commit is contained in:
Eric Pouech 2000-09-10 03:13:41 +00:00 committed by Alexandre Julliard
parent bd6a0394f5
commit 26501596da
1 changed files with 36 additions and 5 deletions
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41
objects/dib.c
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@ -145,15 +145,46 @@ INT WINAPI StretchDIBits(HDC hdc, INT xDst, INT yDst, INT widthDst,
HBITMAP hBitmap, hOldBitmap; HBITMAP hBitmap, hOldBitmap;
HDC hdcMem; HDC hdcMem;
hBitmap = CreateDIBitmap( hdc, &info->bmiHeader, CBM_INIT,
bits, info, wUsage );
hdcMem = CreateCompatibleDC( hdc ); hdcMem = CreateCompatibleDC( hdc );
hOldBitmap = SelectObject( hdcMem, hBitmap ); if (info->bmiHeader.biCompression == BI_RLE4 ||
info->bmiHeader.biCompression == BI_RLE8) {
/* when RLE compression is used, there may be some gaps (ie the DIB doesn't
* contain all the rectangle described in bmiHeader, but only part of it.
* This mean that those undescribed pixels must be left untouched.
* So, we first copy on a memory bitmap the current content of the
* destination rectangle, blit the DIB bits on top of it - hence leaving
* the gaps untouched -, and blitting the rectangle back.
* This insure that gaps are untouched on the destination rectangle
* Not doing so leads to trashed images (the gaps contain what was on the
* memory bitmap => generally black or garbage)
* Unfortunately, RLE DIBs without gaps will be slowed down. But this is
* another speed vs correctness issue. Anyway, if speed is needed, then the
* pStretchDIBits function shall be implemented.
* ericP (2000/09/09)
*/
hBitmap = CreateCompatibleBitmap(hdc, info->bmiHeader.biWidth,
info->bmiHeader.biHeight);
hOldBitmap = SelectObject( hdcMem, hBitmap );
/* copy existing bitmap from destination dc */
StretchBlt( hdcMem, xSrc, abs(info->bmiHeader.biHeight) - heightSrc - ySrc,
widthSrc, heightSrc, hdc, xDst, yDst, widthDst, heightDst,
dwRop );
SetDIBits(hdcMem, hBitmap, 0, info->bmiHeader.biHeight, bits,
info, DIB_RGB_COLORS);
} else {
hBitmap = CreateDIBitmap( hdc, &info->bmiHeader, CBM_INIT,
bits, info, wUsage );
hOldBitmap = SelectObject( hdcMem, hBitmap );
}
/* Origin for DIBitmap may be bottom left (positive biHeight) or top /* Origin for DIBitmap may be bottom left (positive biHeight) or top
left (negative biHeight) */ left (negative biHeight) */
StretchBlt( hdc, xDst, yDst, widthDst, heightDst, StretchBlt( hdc, xDst, yDst, widthDst, heightDst,
hdcMem, xSrc, abs(info->bmiHeader.biHeight) - heightSrc - ySrc, hdcMem, xSrc, abs(info->bmiHeader.biHeight) - heightSrc - ySrc,
widthSrc, heightSrc, dwRop ); widthSrc, heightSrc, dwRop );
SelectObject( hdcMem, hOldBitmap ); SelectObject( hdcMem, hOldBitmap );
DeleteDC( hdcMem ); DeleteDC( hdcMem );
DeleteObject( hBitmap ); DeleteObject( hBitmap );