[FFmpeg-trac] #10025(undetermined:new): Skewed png images for certain resolutions when making thumbnail

[FFmpeg]

#10025: Skewed png images for certain resolutions when making thumbnail
-------------------------------------+-------------------------------------
             Reporter:  Kevin        |                    Owner:  (none)
  Sallee                             |
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  unspecified  |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------

Old description:

> Summary of the bug:
> How to reproduce:
> {{{
> % ffmpeg -i skew.png -vf
> "scale=force_original_aspect_ratio=decrease:w=2048:h=2048, thumbnail"
> -frames:v 1 skew_thumb.png
> ffmpeg version 5.1.2
> built on OSX
> }}}
>
> For certain PNG image resolutions, the command results in a skewed
> output. I am attaching examples of a PNG that does not cause the skew,
> and one that causes it.
> Previous versions of ffmpeg were not exhibiting this behavior

New description:

 Summary of the bug:
 How to reproduce:
 {{{
 % ffmpeg -i skew.png -vf
 "scale=force_original_aspect_ratio=decrease:w=2048:h=2048, thumbnail"
 -frames:v 1 skew_thumb.png
 ffmpeg version 5.1.2
 built on OSX
 }}}

 For certain PNG image resolutions, the command results in a skewed output.
 I am attaching examples of a PNG that does not cause the skew, and one
 that causes it.
 Previous versions of ffmpeg were not exhibiting this behavior


 The full output of the command failing:

--
Comment (by Kevin Sallee):

 The full output of the command:

 ffmpeg -y -i skew.png -vf
 "scale=force_original_aspect_ratio=decrease:w=2048:h=2048:flags=fast_bilinear,
 thumbnail" -frames:v 1 skew_thumb.png
 ffmpeg version N-107731-g5cdf4c0bed-tessus Copyright (c) 2000-2022 the
 FFmpeg developers
   built with Apple clang version 11.0.0 (clang-1100.0.33.17)
   configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg --extra-
 version=tessus --enable-avisynth --enable-fontconfig --enable-gpl
 --enable-libaom --enable-libass --enable-libbluray --enable-libdav1d
 --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-
 libmp3lame --enable-libmysofa --enable-libopencore-amrnb --enable-
 libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-
 libopus --enable-librubberband --enable-libshine --enable-libsnappy
 --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame
 --enable-libvidstab --enable-libvmaf --enable-libvo-amrwbenc --enable-
 libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-
 libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-libzmq
 --enable-libzvbi --enable-version3 --pkg-config-flags=--static --disable-
 ffplay
   libavutil      57. 32.101 / 57. 32.101
   libavcodec     59. 42.100 / 59. 42.100
   libavformat    59. 30.100 / 59. 30.100
   libavdevice    59.  8.101 / 59.  8.101
   libavfilter     8. 46.101 /  8. 46.101
   libswscale      6.  8.102 /  6.  8.102
   libswresample   4.  8.100 /  4.  8.100
   libpostproc    56.  7.100 / 56.  7.100
 Input #0, png_pipe, from 'skew.png':
   Duration: N/A, bitrate: N/A
   Stream #0:0: Video: png, rgb24(pc), 3121x1776 [SAR 2835:2835 DAR
 3121:1776], 25 fps, 25 tbr, 25 tbn
 Stream mapping:
   Stream #0:0 -> #0:0 (png (native) -> png (native))
 Press [q] to stop, [?] for help
 [Parsed_thumbnail_1 @ 0x7f9cdb8105c0] frame id #0 (pts_time=0.000000)
 selected from a set of 1 images
 Output #0, image2, to 'skew_thumb.png':
   Metadata:
     encoder         : Lavf59.30.100
   Stream #0:0: Video: png, rgb24(pc, gbr/unknown/unknown, progressive),
 2048x1165 [SAR 3635965:3637248 DAR 3121:1776], q=2-31, 200 kb/s, 25 fps,
 25 tbn
     Metadata:
       encoder         : Lavc59.42.100 png
 [image2 @ 0x7f9cdb804f00] The specified filename 'skew_thumb.png' does not
 contain an image sequence pattern or a pattern is invalid.
 [image2 @ 0x7f9cdb804f00] Use a pattern such as %03d for an image sequence
 or use the -update option (with -frames:v 1 if needed) to write a single
 image.
 frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed=
 0x
 video:1314kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: unknown
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10025#comment:2>
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