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Some PNG images get corrupted
Posted: 2012-05-13T18:15:24-07:00
by Jason S
Here's a small 16-bit RGB PNG image with binary transparency:
Run it through "convert", with no options. Using the Cygwin 6.7.6-3 release, the top row gets corrupted:
With 6.7.6-9 on Cygwin, I get similar but not identical corruption. With a Linux 6.7.6-9 Q16 build, just two pixels near the top incorrectly become transparent. With a native Windows build, I haven't seen any corruption.
The same problem occurs with other (all?) small (under about 750 pixels?) images of the same type.
Re: Some PNG images get corrupted
Posted: 2012-05-13T18:22:35-07:00
by fmw42
I don't see any corruption of your input or output image. Repeating
convert ctest.png ctest2.png
Still no corruption.
compare -metric rmse ctest.png ctest2.png null:
0 (0)
I am using IM 6.7.6.10 beta (doing some testing of other issues), Mac OSX Snow Leopard.
If I compare your two images, I see some colorization differences. This may(?) be due to the recent changes in how IM handles sRGB especially in PNG from sRGB with rendering intent=undefined to sRGB with rendering intent=perceptual. However, it should not affect the actual pixel data, only the viewing of the images. So I am not sure why you get this much difference.
compare -metric rmse ctest.png ctest-cygwin-6.7.6-3.png null:
1406.47 (0.0214614)
You could try upgrading as I don't see that issue.
I will defer to the IM developers on this one, if it is not caused by the change in rendering intent and possible bugs along the way.
Re: Some PNG images get corrupted
Posted: 2012-05-13T21:04:40-07:00
by Jason S
There is some unknown factor that determines whether this problem occurs, so I don't expect everyone to be able to reproduce it.
But if you're suggesting the two images in my report are visually identical to you, I don't really know what to say.
Note that 'compare' appears to also be affected by the problem, so its calculations on these images should not be trusted.
Re: Some PNG images get corrupted
Posted: 2012-05-13T22:13:39-07:00
by fmw42
Jason S wrote:There is some unknown factor that determines whether this problem occurs, so I don't expect everyone to be able to reproduce it.
But if you're suggesting the two images in my report are visually identical to you, I don't really know what to say.
Note that 'compare' appears to also be affected by the problem, so its calculations on these images should not be trusted.
Sorry if I was not clear. I said there was a slight visual color difference and that the compare shows a significant difference, but only with the images you presented. I could not reproduce the situation as my own processing and compare showed no difference visually or in the pixel data.
Re: Some PNG images get corrupted
Posted: 2012-05-16T17:41:39-07:00
by Jason S
Using valgrind, I get dozens of "uninitialised value" warnings that I don't get with other types of PNG images.
For example,
Code: Select all
Use of uninitialised value of size 8
at 0x4C2A291: memcpy (mc_replace_strmem.c:635)
by 0x5296466: ??? (in /lib/x86_64-linux-gnu/libz.so.1.2.3.4)
by 0x5296937: ??? (in /lib/x86_64-linux-gnu/libz.so.1.2.3.4)
by 0x5297B49: deflate (in /lib/x86_64-linux-gnu/libz.so.1.2.3.4)
by 0x5078F65: ??? (in /lib/x86_64-linux-gnu/libpng12.so.0.46.0)
by 0x50793DA: ??? (in /lib/x86_64-linux-gnu/libpng12.so.0.46.0)
by 0x507D025: png_write_row (in /lib/x86_64-linux-gnu/libpng12.so.0.46.0)
by 0x4FB609: WriteOnePNGImage (png.c:10487)
by 0x4FF8B5: WritePNGImage (png.c:11576)
by 0x540298: WriteImage (constitute.c:1228)
by 0x540B4F: WriteImages (constitute.c:1377)
by 0x5DB9A4: ConvertImageCommand (convert.c:3026)
Re: Some PNG images get corrupted
Posted: 2012-05-17T04:32:59-07:00
by glennrp
Jasom, I'm not sure this is relevant but from the traceback you seem to be using an old libpng (1.2.46) and zlib (1.2.3.4)
That should be OK but you never know... I don't see anything in the libpng CHANGES file that would explain a
change in behavior from 1.2.46 to the current 1.2.49 though.
Does "convert -list format | grep PNG" say the same?
Re: Some PNG images get corrupted
Posted: 2012-05-17T05:10:55-07:00
by glennrp
It may be due to png.c doing things like
- quantum_info->format=UndefinedQuantumFormat;
quantum_info->depth=image_depth;
instead of using
- SetQuantumDepth(...) and SetQuantumFormat(...)
It's possible that some members of quantum_info are not being
set this way. I will look into this more later.
Re: Some PNG images get corrupted
Posted: 2012-05-17T13:31:47-07:00
by Jason S
I was using an old version version of libpng and zlib in that case (because I used what was provided by the Ubuntu distribution managers). Sorry for the lack of details, but I didn't expect this to be hard for others to reproduce.
I've had a chance to try it with the latest libpng, and it didn't help.
Code: Select all
PNG* rw- Portable Network Graphics (libpng 1.5.10)
"valgrind --track-origins=yes" gives more details, such as
Code: Select all
Conditional jump or move depends on uninitialised value(s)
at 0x6A3CCE: png_write_find_filter (pngwutil.c:2620)
by 0x6A0D13: png_write_row (pngwrite.c:814)
by 0x533118: WriteOnePNGImage (png.c:10487)
by 0x536ADF: WritePNGImage (png.c:11576)
by 0x576FD2: WriteImage (constitute.c:1228)
by 0x5793D0: WriteImages (constitute.c:1377)
by 0x63C838: ConvertImageCommand (convert.c:3026)
by 0x657AA5: MagickCommandGenesis (mogrify.c:159)
by 0x40AC24: main (convert.c:81)
Uninitialised value was created by a heap allocation
at 0x4C2415D: malloc (vg_replace_malloc.c:195)
by 0x555B2E: OpenPixelCache (cache.c:3913)
by 0x55876A: GetImagePixelCache (cache.c:2092)
by 0x5589B1: QueueAuthenticPixelCacheNexus (cache.c:4367)
by 0x5568B0: QueueAuthenticPixels (cache.c:4530)
by 0x528819: ReadOnePNGImage (png.c:2888)
by 0x529140: ReadPNGImage (png.c:3670)
by 0x577967: ReadImage (constitute.c:590)
by 0x578B4A: ReadImages (constitute.c:903)
by 0x63A725: ConvertImageCommand (convert.c:598)
by 0x657AA5: MagickCommandGenesis (mogrify.c:159)
by 0x40AC24: main (convert.c:81)
which suggests a patch that is probably overkill, but does seem to work.
Code: Select all
--- magick/cache.c.orig 2012-05-06 14:59:24.000000000 -0400
+++ magick/cache.c 2012-05-17 15:26:03.143246372 -0400
@@ -3912,6 +3912,7 @@
cache_info->mapped=MagickFalse;
cache_info->pixels=(PixelPacket *) AcquireMagickMemory((size_t)
cache_info->length);
+ if (cache_info->pixels) ResetMagickMemory(cache_info->pixels,0,cache_info->length);
if (cache_info->pixels == (PixelPacket *) NULL)
{
cache_info->mapped=MagickTrue;