[FFmpeg-trac] #172(undetermined:new): PNG 1bpp grayscale image decodes incorrectly

[FFmpeg]

#172: PNG 1bpp grayscale image decodes incorrectly
--------------------------+--------------------------
 Reporter:  ami_stuff     |        Type:  defect
   Status:  new           |    Priority:  normal
Component:  undetermined  |     Version:  unspecified
 Keywords:                |  Blocked By:
 Blocking:                |  Reproduced:  0
 Analyzed:  0             |
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 Issue 1416

 {{{
 Author: ami_stuff       Date: 2009-09-25.23:20:46

 Attached PNG image is 1bpp grayscale and decodes incorrectly.

 This color mode (1bpp grayscale) seems to to be supported by FFmpeg.

 pngdec.c:
 "else if (s->bit_depth == 1 &&
 s->color_type == PNG_COLOR_TYPE_GRAY) {
 avctx->pix_fmt = PIX_FMT_MONOBLACK;"

 PS. I have also PNG 4bpp color/grayscale images which decodes incorrectly.
 If
 there is a need I can upload.

 --------

 C:\>ffmpeg -i Test_1bpp_grayscale.png
 FFmpeg version SVN-r19926, Copyright (c) 2000-2009 Fabrice Bellard, et al.
   configuration: --enable-memalign-hack --prefix=/mingw --cross-
 prefix=i686-ming
 w32- --cc=ccache-i686-mingw32-gcc --target-os=mingw32 --arch=i686
 --cpu=i686 --e
 nable-avisynth --enable-gpl --enable-zlib --enable-bzlib --enable-libgsm
 --enabl
 e-libfaad --enable-pthreads --enable-libvorbis --enable-libtheora
 --enable-libsp
 eex --enable-libmp3lame --enable-libopenjpeg --enable-libxvid --enable-
 libschroe
 dinger --enable-libx264
   libavutil     50. 3. 0 / 50. 3. 0
   libavcodec    52.35. 0 / 52.35. 0
   libavformat   52.38. 0 / 52.38. 0
   libavdevice   52. 2. 0 / 52. 2. 0
   libswscale     0. 7. 1 /  0. 7. 1
   built on Sep 20 2009 04:03:00, gcc: 4.2.4
 Input #0, image2, from 'Test_1bpp_grayscale.png':
   Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
     Stream #0.0: Video: png, pal8, 1024x768, 25 tbr, 25 tbn, 25 tbc
 At least one output file must be specified
 }}}

 {{{
 Author: kostya  Date: 2009-09-28.05:57:15

 quite probably PNG file says "palettized data with 1 bit per entry"
 and lavc PNG decoder still treats it as 8 bit per entry, so that
 condition you cited is not triggered because of different s-
 >color_type
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/172>
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