Is it possible to smooth a scaled TBitmap in Delphi?

I am using Stretched=True on a TImage with a 256x256 bitmap. This gets scaled down by 1,2,4 or 8. As expected, text on the bitmap gets more horrible the more I de开发者_StackOverflowpart from '1'. I notice though that Windows 7 explorer renders a scaled down version of the bitmap 'softer' and more pleasing. Is it possible to 'blur' a TBitmap in this way?

I suppose you mean Stretched = True on a TImage, not on A TBitmap.

Unfortunately TImage has no resamplers built in, when it comes to resizing images in it. My recommendation would be to use Graphics32 as it supports a variety of resamplers (some are better for increasing size others for reducing size)

By using the HALFTONE StretchBltMode, you will get smoother results than the normal stretchdraw. This will only work in windows 2000 and later

procedure SmoothResize();
var pt:TPoint;
    h: HDC;
begin
  h := imgMainPicture.Canvas.Handle;
  // Previous call to StretchDraw
  // imgMainPicture.Canvas.StretchDraw(Rect(0, 0, imgMainPicture.Width - 1,
  // imgMainPicture.Height - 1), curPicture.AnnotatedBitmap);
  // Normal StretchDraw uses STRETCH_DELETESCANS as StretchBltMode , HALFTONE should give better results
  GetBrushOrgEx(h, pt);
  SetStretchBltMode(h, HALFTONE);
  SetBrushOrgEx(h, pt.x, pt.y, @pt);
  StretchBlt(h, 0, 0, imgMainPicture.Width - 1,
    imgMainPicture.Height - 1, curPicture.AnnotatedBitmap.Canvas.Handle,
    0, 0, curPicture.Width,curPicture.Height,SRCCOPY);
end;