Shifted rows on multiple images

[Shnatsel]

The following image

gets decoded like this

Here's an rchive with 92 more examples showing significant mismatch compared to imagemagick:
https://mega.nz/file/M90XCIwK#cyiSqTo3KhtGCm7Fw6RxKoKH4sfraHEzC6wGA2UqD-8

At least some of them show the same issue, but there may be other issues in there as well.

Tested on commit b923233

[Shnatsel]

Here's the shell script I use for testing:

#!/bin/sh

set -e

input="$1"
output="$(mktemp --tmpdir result_XXXXXXXXXXXXX.ppm)"
trap "rm -f "$output"" EXIT

if ! yes | /home/shnatsel/Code/zune-image/target/release/zune --input "$input" --out "$output" >/dev/null 2>&1; then
    echo "Failed to decode $input" 1>&2
    exit 1
fi
similarity=$(compare -quiet -metric RMSE "$input[0]" "$output" /dev/null 2>&1) || true
echo "$similarity $input"

The compare command is part of imagemagick, make sure you have it installed.

[Shnatsel]

And I have many more images showing mismatches compared to imagemagick, but I'm not sure how many distinct issues there actually are. I'll re-run the test once this batch is fixed.

[etemesi254]

Thank you for the corpus, will look into it

[Shnatsel]

At a glance it seems all these images have the same issue.

[etemesi254]

Yea, it's probably a wrong stride calculation somewhere.