Color Loss

[sosso]

Noticing that many of my images are experiencing color loss, even without lowering the quality or doing any resizing. Any idea what's causing it? Additionally, the proxied is about 200KB larger in this first instance:

Original:

Proxied:

[willnorris]

If you're not changing the quality or resizing, what options are you passing to the proxy?

[jacobbudin]

@sosso The original image has an embedded ICC color management profile, while the proxy output image does not. This absence explains the visual difference.

[datasage]

The cause here is that image/jpeg sends every APPn marker except APP0 and APP14 to decoder.ignore, and Encode writes no APP segments at all — so the source's embedded ICC profile can't survive Decode → Encode, and the untagged result gets rendered as sRGB. That's why a wide-gamut original comes back desaturated even with no resize and no quality change, as in the images above.

Measured at /x80/ against a correct color-managed render: a Display P3 source is 3.64% RMSE off, an Adobe RGB source 4.93%.

I've opened #505 with a passthroughICC flag (off by default) that carries the profile over, which brings both to ~0.3% — JPEG quantization noise. Happy to move the design discussion back here if that's preferred.