Standardising colorspaces

[OrangeDog]

Right, here are the ones starting with the CMYK original: http://postimage.org/image/dvwkfrxz5/

And here is the opposite problem, starting from an sRGB original (iPhone screenshot in Safari): http://postimage.org/image/5ybr18ltz/

As an aside, you can see Safari has done a horrible job, which is why I need to do this standardization.

[snibgo]

Okay. Looking at those, and examining the pixels with Gimp's eyedropper, of the first group:

(1) orig.jpg has a blue cast. The man's sweater, child's hat and sweater, pushchair footrest, the dog and tree shadows across the path all show this. Skin tones are grey.

(2) profile.jpg compared to orig.jpg: The white/gray objects are more neutral; skin is more natural. IMO, a vast improvement.

(3) rgb.jpg seems the same as orig.jpg.

(4) srgb.jpg has the gamma too high. It may also have a blue colour cast.



Of the second group:

(1) orig.png blue cast; no detail in shadows.

(2) rgb.png even worse colour cast, which might be caused by the downshift in tones, which might be a gamma problem. I don't know what processing you did here. Perhaps "-colorspace RGB", which would downshift the tones. If the original is sRGB, you don't need any colour conversion.

So, profile.jpg seems the best version, giving the more neutral colour to objects that I suppose were neutral in real life. I suspect (but have no way of knowing) this is the most technically accurate image. However, you might prefer the blue colour cast, which gives a "chillier" feel.

[OrangeDog]

There's the problem - I have no idea what the uploader intends, and am trying to not change it from what they're likely to think it looks like.

[snibgo]

Then I suggest you aim for technical correctness, rather than what it looks like. If an uploader sends an image with purple grass and green sky, that's what you need to deal with. If it's already sRGB, just leave it. If it has a profile that isn't sRGB, change the profile to sRGB. If it has no profile but the colorspace is CMYK or anything other than sRGB, change the colorspace.

[OrangeDog]

Me trying to do that is what this whole thread's about, but changing CMYK to sRGB changes the appearance!

[snibgo]

And round we go again...

I think I've offered all the help I can.