Devisualization.Image
Marco Leise via Digitalmars-d-announce
digitalmars-d-announce at puremagic.com
Tue Nov 18 15:53:53 PST 2014
Am Wed, 19 Nov 2014 00:35:09 +0100
schrieb Marco Leise <Marco.Leise at gmx.de>:
> > I have working PNG export in my image processing package, part of dlib:
> > https://github.com/gecko0307/dlib
> > There're also importers for BMP and TGA.
>
> I also just wrote a TGA importer and found RLE and 16-bit in
> particular badly supported on Linux. E.g. eye-of-gnome
> (Gnome's picture viewer) doesn't correctly restore the last
> pixel's color in an RLE image and most software doesn't handle
> 16-bit at all. Add to that, that the specs are not very
> specific as to what allowed values are and you get all
> sorts of funny implementations quirks.
For example:
- the original Targa paint software TIPS used to store a
palette even for TrueColor images, meaning you should
actually calculate the data offset as header + id + palette
even for 24- and 32-bit images.
- the number of channels for a TrueColor TGA is always 3, plus
as many attribute bits as given in the descriptor.
If you only support 8-bits per color channel, you should check
if bitsPerPixel is >= 24. Otherwise, bitsPerPixel == 16 would
be interpreted as a two color channel image instead of three
channels à 5-bits. And bitsPerPixel == 15 would become a one
channel image. :p
The 15-/16-bit variants were used quite a bit in the early
days of 3D games, like in the menu graphics for "Trespasser".
They are the same except that 16-bit allows for an additional
attribute bit that could be used for a transparency mask.
--
Marco
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