IFACEMETHODIMP PreviewBase::GetThumbnail(UINT cx, HBITMAP *phbmp, WTS_ALPHATYPE *pdwAlpha)
{
BaseEngine *engine = GetEngine();
if (!engine)
return E_FAIL;
RectD page = engine->Transform(engine->PageMediabox(1), 1, 1.0, 0);
float zoom = min(cx / (float)page.dx, cx / (float)page.dy) - 0.001f;
RectI thumb = RectD(0, 0, page.dx * zoom, page.dy * zoom).Round();
BITMAPINFO bmi = { 0 };
bmi.bmiHeader.biSize = sizeof(bmi.bmiHeader);
bmi.bmiHeader.biHeight = thumb.dy;
bmi.bmiHeader.biWidth = thumb.dx;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biCompression = BI_RGB;
unsigned char *bmpData = NULL;
HBITMAP hthumb = CreateDIBSection(NULL, &bmi, DIB_RGB_COLORS, (void **)&bmpData, NULL, 0);
if (!hthumb)
return E_OUTOFMEMORY;
page = engine->Transform(thumb.Convert<double>(), 1, zoom, 0, true);
RenderedBitmap *bmp = engine->RenderBitmap(1, zoom, 0, &page);
HDC hdc = GetDC(NULL);
if (bmp && GetDIBits(hdc, bmp->GetBitmap(), 0, thumb.dy, bmpData, &bmi, DIB_RGB_COLORS)) {
// cf. http://msdn.microsoft.com/en-us/library/bb774612(v=VS.85).aspx
for (int i = 0; i < thumb.dx * thumb.dy; i++)
bmpData[4 * i + 3] = 0xFF;
*phbmp = hthumb;
if (pdwAlpha)
*pdwAlpha = WTSAT_RGB;
}
else {
DeleteObject(hthumb);
hthumb = NULL;
}
ReleaseDC(NULL, hdc);
delete bmp;
return hthumb ? S_OK : E_NOTIMPL;
}
