Vertical stitch: Take a set of (in this case 598) frames from a phone scroll recording, and rebuild the original list being scrolled

vertstitch.sh

#!/bin/bash
BLOBH=256
BLOBX=0
BLOBY=0

convert az0001.jpg final.png
BLOBW=$(identify -format "%w" final.png)
FULLWIDTH=$(identify -format "%w" final.png)

for filenum in {1..597}; do
    filenun=$(($filenum+1))
    INA=$(printf "az%04d.jpg" $filenum)
    INB=$(printf "az%04d.jpg" $filenun)
    convert $INA -crop ${BLOBW}x+${BLOBX}+0 a.png
    convert $INB -crop ${BLOBW}x${BLOBH}+${BLOBX}+0 b.png

    XHEIGHT=$(identify -format "%h" a.png)
    FULLHEIGHT=$(identify -format "%h" final.png)

    lines=0
    mindiff=1048576
    minlines=0
    while [ 1 == 1 ]; do
        OFFSET=$((XHEIGHT-BLOBH-1-lines))
        if [ $OFFSET -lt 0 ]; then break; fi
        diff=$(convert a.png -crop ${BLOBW}x${BLOBH}+${BLOBX}+${OFFSET} +repage \
            b.png \
            -compose difference -composite \
            \( +clone -evaluate set 0 \) -metric RMSE -compare -format "%[distortion]" info:)
        if [ $(echo "${diff} < ${mindiff}" | bc) == '1' ]; then
            mindiff=$diff
            minlines=$lines
        fi
        echo $diff:$lines
        ((lines++))
    done

    rm a.png b.png
    fulloffs=$((FULLHEIGHT-BLOBH-1-minlines))
    echo $INA:$minlines:$fulloffs
    if [ $fulloffs -gt 0 ]; then
        convert final.png -crop ${FULLWIDTH}x${fulloffs}+0+0 $INB -append final.png
    fi
done