JPEG loading color difference FPReadJPEG

[ttomas]

@circular Yes i play with AdobeRGBAToXYZA. Is StdRGB same as sRGB? I think we need AdobeRGBA -> XYZA -> sRGB transformation.
In extendedcolorspaces.inc is missing function XYZAToStdRGBA. I copy code from XYZAToAdobeRGBA to XYZAToStdRGBA and change matrix for sRGB from
http://brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
Then try p^ := XYZAToStdRGBA(AdobeRGBAToXYZA(p^)).ToBGRAPixel;
Result is corrupted image, need some help.

Code: Pascal  [Select][+][-]

1. function XYZAToStdRGBA(const AXYZA: TXYZA; const AReferenceWhite: TXYZReferenceWhite): TStdRGBA;
2. var R,G,B: single;
3.   ad: TXYZA;
4. begin
5.   ad := AXYZA;
6.   if AReferenceWhite.Illuminant = 'D50' then
7.   begin
8.     ad.ChromaticAdapt(AReferenceWhite, ReferenceWhite2D50);
9.     with ad do
10.     begin
11.       R := Clamp(3.1338561*X - 1.6168667*Y - 0.4906146*Z,0,1);
12.       G := Clamp(-0.9787684*X + 1.9161415*Y + 0.0334540*Z,0,1);
13.       B := Clamp(0.0719453*X - 0.2289914*Y + 1.4052427*Z,0,1);
14.     end;
15.   end else
16.   begin
17.     ad.ChromaticAdapt(AReferenceWhite, ReferenceWhite2D65);
18.     with ad do
19.     begin
20.       R := Clamp(3.2404542*X - 1.5371385*Y - 0.4985314*Z,0,1);
21.       G := Clamp(-0.9692660*X + 1.8760108*Y + 0.0415560*Z,0,1);
22.       B := Clamp(0.0556434*X - 0.2040259*Y + 1.0572252*Z,0,1);
23.     end;
24.   end;
25.   result.red := GammaCompressionTab[round(R*65535)];
26.   result.green := GammaCompressionTab[round(G*65535)];
27.   result.blue := GammaCompressionTab[round(B*65535)];
28.   result.alpha := ClampInt(round(AXYZA.alpha*255),0,255);
29. end;  

[ttomas]

I change result to

Code: Pascal  [Select][+][-]

1.   result.red := R;
2.   result.green := G;
3.   result.blue := B;
4.  

Now I have correct image, but colors are same as using TAdobeRGBA.New(p^.red, p^.green, p^.blue);

[circular]

Yes StdRGB stands for sRGB (s means standard).

Ok so you find the same result.

[ttomas]

Yes without correction just open and save image result is noticeable lot darker.
TAdobeRGBA and XYZAToStdRGBA(AdobeRGBAToXYZA(p^)) visually have same result, little lighter then original. Maybe client will not notice :-).

[torumyax]

I'm also interested in this since I developed an image viewer. Recently I noticed a color difference too. When I display a image in a browser or some other windows viewer developed in C#, it looks a lot different. After some googling, I learned about the ICC profile. Any progress? Thank you!