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Martijn
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 Posted: Tue Nov 23, 2004 7:53 am Post subject: StretchBlt doesn't do half-toning |
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Hi,
I have the following problem: I use a TPaintBox on a ScrollBox
to display document pages. Each page is rendered to an in-
memory bitmap (1 bit per pixel, approx 600 dpi). When I use
BitBlt to copy the pixels to the PaintBox' Canvas->Handle all
looks good (but very BIG).
However, when I use StretchBlt to view a compressed version of
the (large) bitmap in the PaintBox, it looks awful. When I
preceed the StretchBlt with this call
SetStretchBltMode(PaintBox->Canvas->Handle, STRETCH_HALFTONE);
I would expect the image to show shades of grey (anti-aliasing),
but it doesn't.
What am I doing wrong?
NOTE: I use BCB6 on WinXP
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Bruce Salzman
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| Posted: Tue Nov 23, 2004 5:16 pm Post subject: Re: StretchBlt doesn't do half-toning |
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| Quote: | I have the following problem: I use a TPaintBox on a ScrollBox
to display document pages. Each page is rendered to an in-
memory bitmap (1 bit per pixel, approx 600 dpi). When I use
BitBlt to copy the pixels to the PaintBox' Canvas->Handle all
looks good (but very BIG).
However, when I use StretchBlt to view a compressed version of
the (large) bitmap in the PaintBox, it looks awful. When I
preceed the StretchBlt with this call
SetStretchBltMode(PaintBox->Canvas->Handle, STRETCH_HALFTONE);
I would expect the image to show shades of grey (anti-aliasing),
but it doesn't.
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I wouldn't expect STRETCH_HALFTONE to work with a monochrome (1bpp)
bitmap. What happens if you use one of the other modes?
Regards,
Bruce
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