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sRGB or RGB


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Does PDN use internally sRGB or RGB color coding? For example, when I scan an image from within PDN and use the default Windows color profile (sRGB), is then the image in PDN sRGB-encoded or not?

I'd say that it is sRGB encoded. But almost all PDN tools and plugins do not bother to decode it before manipulating it, am I correct? The correct processing sequence should be

sRGB -> RGB -> image manipulation -> RGB -> sRGB

while most tools manipulate the sRGB image directly:

sRGB -> manipulation -> sRGB.

Am I right?

Martin.

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I know that PDN has no explicit means to work with color profiles. But it cannot avoid working with color profiles implicitly - because scanners, printers, image files (when loading/saving) and Windows itself do use them. Thus I expect that when scanning, PDN receives sRGB encoded image. when printing, it sends the sRGB image to the printer without decoding it (the Windows do the decoding then, I suppose). But what does PDN do when loading/saving an image from/to disk? In particular, when a loaded image uses different color space, does PDN convert the image to RGB, or to sRGB? And does PDN do that consistently, or is the result sometimes RGB, and sometimes sRGB?

I am asking because I needed to perfor some a little more complex calculations on scanned images using the CodeLab, and the results were not satisfactory. The results improved when I considered the image sRGB encoded, but they were still far from perfect.

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I guess you know color management is a complex thing. You can not do a calculation from sRGB to RGB because RGB alone means nothing. You always have to define the interpretation of the RGB values (i.e. sRGB or Adobe RGB). The minimal additional information to the RGB values is the definition of the white point and the primaries.

If your image does not provide additional information the assumption that it contains sRGB values is standard nowadays else you should provide your deivce driver the color profile (but Paint.NET does not do this).

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Yes and no, it depends on which kind of calculation you are doing. The basic thing in which sRGB and RGB differ is that RGB is "linear", while sRGB is not. Moreover, the conversion formulas for most pixel characteristics like saturation, HSV value, chroma, luminance use RGB colors, not sRGB encoded (gamma corrected) colors (see Wikipedia).

It seems that PDN has some internal knowledge about sRGB. Because when you e.g. make a printscreen, paste it into PDN and save it as .png, the saved image contains the sRGB flag (ancillary chunk, see Wikipedia). But if you create and edit a new image in PDN and save it as .png, it does NOT contain this sRGB flag, meaning that the image is RGB encoded, not sRGB. (And this is correct behavior, in my opinion.)

And thus I repeat my original question: When I scan an image with PDN, is the image sRGB encoded or not? It should be, I suppose.

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