Lossless PNGs optimization upon their appearance in "report" and its subdirectories

[montehurd]

Reduces PNG file sizes by roughly 30%

Monitors "report" and its subdirectories - isn't otherwise coupled with Pixel code

Quick enough that it doesn't appear to interfere with the BackstopJS image comparison process - running it locally I haven't noticed any odd breakage

Optipng performs the optimization, "-o2" level seems a good balance between speed and file size reduction

Restarts itself if the process ever goes down

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EDIT: it's closer to 20%

This calculate the average png size reduction from the pixel-png-optimizer-1 container logs:

docker logs pixel-png-optimizer-1 2>&1 | grep "reduction" | sed 's/.= (.)%/\1/' | sort -nr | awk '{sum+=$1; count++} END {if (count > 0) printf "Average: %.2f\n", sum/count; else print "No matching lines found."}'

[montehurd]

Peter H and I could smoke test this on the Horizon box first if folks prefer that

[montehurd]

I suppose I could also move the three new files into an "optimizePNG" folder 🤔

[montehurd]

The lock file prevents this line from triggering another inotifywait create event

(exiftool is used to write "OptimizedWithOptiPNG" to the image's "Software" metadata so there’s an easy way to check if an image has already been optimized, see line 30)

[montehurd]

An alternative approach to monitoring directories for the appearance of pngs would be to run the optimize_png func periodically on every png recursively found in "report" and its subdirs (optimize_png checks metadata to see if an image was already optimized so it should be safe to call more than once on a given image), but I suspect that approach would spike resource usage pretty hard while it churned through unoptimized pngs. We may still want such a func we could call once to optimize all images from past tests. I can add that pretty easily if needed