pngeq

Overview ¶

Command pngeq says whether the PNG images of two trees hold the same pixels:

pngeq GENERATED REFERENCE

Every .png under GENERATED is decoded, with its counterpart under REFERENCE, to 8-bit non-premultiplied RGBA, and the two are compared channel by channel.

⛔ It exists because byte equality answers the wrong question. A brand kit moved to its own repository and regenerated there differed in 65 of 73 files, byte for byte -- and in none of its 51 PNGs, pixel for pixel: a newer encoder had compressed the same pictures differently. Without this, "the kit does not reproduce" would have been the verdict, and it was false.