Images get darker when resized

[GHF]

I had some issues with images getting darker when downsampled, which I suspected (and mostly confirmed) was due to sharp's default pipeline being non-colorspace/gamma-aware.

Downsampling the Eric Brasseur test image from this:

to 50% produces this:

when I enable sharp's linear 16-bit depth color pipeline, I get very minor changes. But when I also use the gamma() call with default parameters, I get this result, which looks much better:

My experience is that performing additional de-gammaing should not be needed after the colors have already been transformed from the input colorspace to linear RGB. So the fact that the gamma() call is required seems fishy because it suggests sharp's input pipeline isn't doing that colorspace conversion.

[zachleat]

I think this is probably something that we’ll extend via #52 to allow folks to do custom Sharp processing pre-output.

Independently, it might be good to file this upstream on the Sharp repository. Is this related? lovell/sharp#3273

Please subscribe to #52!