JPEGMIN (Bash Script).
The script uses the ImageMagick to determine the best indicator of quality when converting lossless images to jpeg. For calculations using BC.
As a criterion for visual quality using correlation analysis of the state borders:
convert -quality $q "$src" "$tmpfile"
convert -edge 3 "$tmpfile" "$tmpfileedge"
cmppct=`compare -metric NCC "$srcfileedge" "$tmpfileedge" /dev/null 2>&1
In terms of the correlation A correlation is based sigmoid:
NCCsigma=`echo "1-sqrt(1-$cmppct)" | bc`
Avoiding the correlation sigmoid from linearity well characterizes the state borders. In this particular case, the maximum deviation interested in q=60-100.
cmppct=`echo "$q*0.01-1+sqrt(1-$cmppct)" | bc`
It characterizes the beginning of the process avoidance of artifacts at the borders.
PS: State borders - is not the only factor that determines the visual quality. Possible combined application and other filters for activating factors unrelated to the boundaries.
jpegmin-zt-test:
bash jpegmin-zt.sh lena.png
lena-png
result:
lena-jpegmin.jpg
88 -> .342574
Before:462KB After:58KB Saved:404KB(87%)
index:
bash jpemin-zt-test.sh lena.png
lena-jpegmin.csv