image/draw: Draw is slow on Paletted images

[nicks]

I've been investigating an issue where drawing Paletted images seems much slower than other types of image conversion.

AFAIK, it's drawing the image twice?

go/src/image/draw/draw.go

Line 178 in f9ed2f7

drawPaletted(dst0, r, src, sp, false)

It executes the "fast" drawPaletted image, then falls into the default case, and executes the "slow" drawing path? I think there's supposed to be a return there?

[bradfitz]

@nigeltao?

[nigeltao]

You're absolutely right. I'll send out a fix.

[gopherbot]

CL https://golang.org/cl/11858 mentions this issue.

[nicks]

thanks Nigel! that was quick 💨