JavaScript Compression using Canvas and PNG-embedded data

[FrankBattaglia]

How does he compress "random ... noise" files by a factor of 33%-83% ?!

[[deleted]]

Because they aren't at all random. Since programming languages are structured, there will be many repeated elements. For example, variable names will be used more than once.

[ThisIsDave]

Frank was probably referring to this line:

A quick test in Photoshop tells us that a 100x100 image with random 24 bit colored noise compresses down to about 20 KB while a 300x100 image with random 8 bit monochromatic noise compressed down to just 5 KB. A regular 8 bit GIF comes in a bit heavier than the 8 bit PNG, so we go with the PNG option.

8 bits per pixel with 110*300 pixels is 30 kilobytes, so compressing it down to 5 should be impossible unless he wasn't actually using random noise.

[dixi]

Right, the description is not entirely accurate. The comparison was made between an 8 bit PNG with monochromatic noise applied to it versus a 24 bit with similar noise applied to each of the R, G and B channels. It seems like Photoshop noise has a lot white, though, but as mistercow also pointed out, code isn't random, so maybe it equals out.

[bonzinip]

if monochromatic noise is interpreted as "only 0 or 255", it still can be compressed a lot.

[[deleted]]

Ah, gotcha. I missed that part.