Ever wonder why software is so slow...?

Because it's all written by retards.

https://github.com/ArtifexSoftware/jbig2dec/blob/master/jbig2_image.c

Scroll down to jbig2_image_compose_unopt()... and then facepalm. It doesn't take a genius to realise that twiddling an image pixel-by-pixel is going to be dead slow.

>>11

jbig2_image_compose_unopt() is, as the name suggests, the UNOPTIMIZED version.

Nice shitpost.

Also that doesn't matter as it's still being called:
int
jbig2_image_compose(Jbig2Ctx *ctx, Jbig2Image *dst, Jbig2Image *src, int x, int y, Jbig2ComposeOp op)
{
[...]

if (op != JBIG2_COMPOSE_OR) {
/* hand off the the general routine */
return jbig2_image_compose_unopt(ctx, dst, src, x, y, op);
}

[...]
}