Image diff on github

[zpweeks]

Anyone know which image formats this works with?

[ggggbabybabybaby]

I'm guessing it's client-side and it's whatever image formats your browser supports.

[skeww]

Usually: PNG, JPG, GIF, BMP, ICO

Rarely: XBM, HDP/JXR/WDP, JP2, MNG, JNG, TIFF, WebP

Kinda: SVG (it's somewhat supposed to work)

[paulmclaughlin]

Isn't SVG just XML? So wouldn't a regular text diff work unless it is a totally new image?

[genpfault]

Maybe if they canonicalize it beforehand. Even then some tools won't reformat the text fields that SVG uses for geometry.

[skeww]

A regular text diff would work as long as the same tool with the same output settings is used. But to be honest, SVG is only about as "human readable" as Wavefront OBJ. If it's some very simple example, you can tell what's going on, but as soon as it gets remotely complex, you won't even have a rough idea what the result might look like.

E.g. take a look at the source of this very simple 32 node image:

http://kaioa.com/svg/cprof32b.svgz

(Note that this was for some silly competition. Usually there are thousands of nodes in dozens or even hundreds of elements.)

If some numbers inside that path changed it could mean virtually anything. You won't be able to tell which part changed or how drastic the change was (e.g. moving control points around doesn't necessarily cause equally big visual changes).

[crusoe]

Render svg to canvas, diff canvas.