On 17/02/07, Glenn Randers-Pehrson <glennrp comcast.net> wrote:
> pngcrush -bit_depth D -c ColorType input.png
output_ColorType_D.png
>
> However, I just tried making a bit_depth==2 file and
got this:
>
> $ pngcheck -v logo2_pc.png
> File: logo2_pc.png (12920 bytes)
> chunk IHDR at offset 0x0000c, length 13
> 654 x 418 image, 2-bit colormap, non-interlaced
> chunk PLTE at offset 0x00025, length 384: 128 palette
entries
> chunk IDAT at offset 0x001b1, length 12467
> zlib: deflated, 32K window, maximum compression
> chunk IEND at offset 0x03270, length 0
> No errors detected in logo2_pc.png (4 chunks, 81.2%
compression).
Yes, I had a look at pngcrush and manged to completely miss
the '-c'
option. I'll make another attempt with that.
>
> The PLTE chunk should only have 4 entries but it's got
128. Pngcheck
> doesn't detect the error.
>
> >I've tried ImageMagick and Gimp, but unfortunately
they utterly
> >refuse to create less often seen formats such as 2
and 4 bit
> >indexed, 64 bit RGBA etc.
> >
> >The reason I'm looking to generate the set and not
simply
> >download one is that they are to be distributed
along with
> >a public-domain software package as test cases, and
any
> >images I've found online are obviously subject to
copyright.
>
> I believe the "pngsuite" from Willem Schaik
is redistributable.
> Follow the link from the PNG web site.
>
I couldn't see anything about distribution on any of the
pngsuite
pages.
I saw this:
(c) Willem van Schaik
willemschaik.com
Singapore, April 1998
...and this:
PNG Suite images and documentation copyright (c) 1995-1998
Willem van Schaik.
I hope to generate a public domain PNG suite (ideally
without
broken PLTE entries!
thanks,
MC
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I'm not having much luck with pngcrush, unfortunately:
OK: 16_greyscale.png (64x64, 64-bit RGB+alpha,
non-interlaced, 90.5%).
OK: 16_greyscale_alpha.png (64x64, 64-bit RGB+alpha,
non-interlaced, 90.5%).
OK: 16_rgb.png (64x64, 48-bit RGB, non-interlaced, 89.9%).
OK: 16_rgba.png (64x64, 64-bit RGB+alpha, non-interlaced,
90.5%).
OK: 1_indexed.png (64x64, 32-bit RGB+alpha, non-interlaced,
84.7%).
OK: 1_indexed_alpha.png (64x64, 32-bit RGB+alpha,
non-interlaced, 84.7%).
OK: 2_indexed.png (64x64, 32-bit RGB+alpha, non-interlaced,
84.7%).
OK: 2_indexed_alpha.png (64x64, 32-bit RGB+alpha,
non-interlaced, 84.7%).
OK: 3_indexed.png (64x64, 32-bit RGB+alpha, non-interlaced,
84.7%).
OK: 3_indexed_alpha.png (64x64, 32-bit RGB+alpha,
non-interlaced, 84.7%).
OK: 4_greyscale.png (64x64, 32-bit RGB+alpha,
non-interlaced, 84.7%).
OK: 4_greyscale_alpha.png (64x64, 32-bit RGB+alpha,
non-interlaced, 84.7%).
OK: 4_indexed.png (64x64, 32-bit RGB+alpha, non-interlaced,
84.7%).
OK: 4_indexed_alpha.png (64x64, 32-bit RGB+alpha,
non-interlaced, 84.7%).
8_greyscale.png cannot read PNG or MNG signature
ERROR: 8_greyscale.png
8_greyscale_alpha.png cannot read PNG or MNG signature
ERROR: 8_greyscale_alpha.png
OK: 8_indexed.png (64x64, 32-bit RGB+alpha, non-interlaced,
84.7%).
OK: 8_indexed_alpha.png (64x64, 32-bit RGB+alpha,
non-interlaced, 84.7%).
OK: 8_rgb.png (64x64, 24-bit RGB, non-interlaced, 84.2%).
OK: 8_rgba.png (64x64, 32-bit RGB+alpha, non-interlaced,
84.7%).
It managed to generate 4 correct PNG files out of a possible
18, and dumped
core after generating any grayscale image.
It may be a case of loading a baseline TIFF image and
generating the PNGs
using libpng and C directly. I was hoping to avoid that but
it seems that
there's nothing (on my platform at least) that can actually
manage to
carry out instructions...
thanks,
MC
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