better StretchBlt/resample Mode?!?

[Hans van den Berg]

Hi,

For downsizing bitmaps I'm always using TCanvas' CopyRect. Before
calling CopyRect I'm used to setting the StretchBltMode with
SetStretchBltMode. This function allows to set the bitmap stretching
mode in the specified device context. However, the number of stretching
modes to choose from for color images are rather limited and the
resizing results not as good as true resampling by certain commercial
programmes.

The choice is between STRETCH_DELETESCANS (a Boolean AND operation using
the color values for the eliminated and existing pixels) or
STRETCH_ANDSCANS (deletes all eliminated lines of pixels without trying
to preserve their information). Though these methods differ I see no
actual difference in the resulting pictures.

Does anyone have a clue how to get a better resampling quality?

Thanks in advance!

Hans van den Berg

[Earl F. Glynn]

Hans van den Berg <vdp...@ccer.nl> wrote in message
news:381D7B98...@ccer.nl...

> Does anyone have a clue how to get a better resampling quality?

Try the "Resampling" links at (in Section C):
http://www.efg2.com/Lab/Library/Delphi/Graphics/Algorithms.htm

___
efg

Earl F. Glynn E-Mail: Earl...@att.net
Overland Park, KS USA

efg's Computer Lab: http://www.efg2.com/Lab