convert translates upside down some picture when converting from jpg to tga

[Thomas Debesse]

When I convert some jpg image to tga format, the tga image is upside down.

The bug only appears with some jpg images, not all. I can convert thousands of jpg images without problems but in some rare images the bug occurs.

You can find three jpg images that are known to fail there:
https://dl.illwieckz.net/b/imagemagick/bugs/convert-jpg-to-tga-upside-down/convert-jpg-to-tga-upside-down-samples.zip
I also attach to this bug report the smallest sample I have.

If I convert from jpg to png, the png is ok
If I convert from jpg to png then from png to tga, the tga is ok
If I convert from jpg to tga, the tga is upside down

You can reproduce by downloading the samples, then run this code in the directory containing the samples:

for i in *.jpg
do
    n="$(basename "${i}" '.jpg')"
    convert "${i}" "${n}.png"
    convert "${i}" "${n}.tga"
done

You can have a look of the result there:
https://dl.illwieckz.net/b/imagemagick/bugs/convert-jpg-to-tga-upside-down/convert-jpg-to-tga-upside-down.png

You can also download this script there:
https://dl.illwieckz.net/b/imagemagick/bugs/convert-jpg-to-tga-upside-down/convert-jpg-to-tga-upside-down.sh

ProblemType: Bug
DistroRelease: Ubuntu 19.04
Package: imagemagick-6.q16 8:6.9.10.14+dfsg-7ubuntu2.2
ProcVersionSignature: Ubuntu 5.0.0-21.22-generic 5.0.15
Uname: Linux 5.0.0-21-generic x86_64
ApportVersion: 2.20.10-0ubuntu27.1
Architecture: amd64
CurrentDesktop: GNOME
Date: Sun Aug 4 01:59:00 2019
SourcePackage: imagemagick
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.default.apport: [modified]
mtime.conffile..etc.default.apport: 2018-06-16T17:39:00.798346

[Thomas Debesse (illwieckz)]

Bad news, sometime the converted png from jpg displays properly but is then set upside-down when converting from png to tga.

I updated the screenshot of the bug:
https://dl.illwieckz.net/b/imagemagick/bugs/convert-jpg-to-tga-upside-down/convert-jpg-to-tga-upside-down.png

And the script to reproduce:
https://dl.illwieckz.net/b/imagemagick/bugs/convert-jpg-to-tga-upside-down/convert-jpg-to-tga-upside-down.sh

Which now looks like this:

for i in *.jpg
do
    n="$(basename "${i}" '.jpg')"
    convert "${i}" "${n}.png"
    convert "${i}" "${n}.tga"
    convert "${n}.png" "${n}.png.tga"
done

When I said converting from jpg to png to tga worked, in fact I had only tested with one file. It's not always true. With the provided "noships.jpg" file, the bug is carried over the png.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.