sRGB conversions to and from CIE XYZ incorrect

Name: jk109818 Date: 10/08/2002


FULL PRODUCT VERSION :
java version "1.4.1"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.1-b21)
Java HotSpot(TM) Client VM (build 1.4.1-b21, mixed mode)

FULL OPERATING SYSTEM VERSION :
Microsoft Windows 2000 [Version 5.00.2195]

A DESCRIPTION OF THE PROBLEM :
The methods toCIEXYZ and fromCIEXYZ should when used on the
sRGB color space should take you from an sRGB color to the
XYZ equivalent and then back (approximately) to the color
you started with. Unfortunately the resulting color differs
substantially from the initial color.
As sRGB is an invertible color space, one or both of the
transformations must be erroneous.

Running the same test with a colour space such as
AdobeRGB98 works successfully. This color space is
specified using a gamma instead of lookup tables. This
suggests that something is wrong with the handling of the
lookup tables.

Tests on color spaces derived from the profile for an Epson
Stylus Photo 2100 (2200 in the US?) printer, produce much
larger anomalies.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Run the attached code.
2.
3.

EXPECTED VERSUS ACTUAL BEHAVIOR :
The colour on the right of each line should be a close
match to that at the beginning of the same line.

Color 0.0 1.0 0.0 ==> XYZ 0.395813 0.71173096 0.08981323
==> color 0.10215915 0.9881895 0.02839704
Color 0.0 0.8 0.0 ==> XYZ 0.23876953 0.42974854 0.05419922
==> color 0.059632257 0.7904631 0.022186618
Color 0.0 0.6 0.0 ==> XYZ 0.1260376 0.22677612 0.028656006
==> color 0.041290913 0.5931945 0.013351644

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.color.ColorSpace;

class TestColorSpace
{
public static void main(String[] args)
{
ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_sRGB);
float[] rgb = new float[3];
float[] g = new float[] {1.0f, 0.8f, 0.6f};
rgb[0] = 0;
rgb[2] = 0;
for (int i=0; i<g.length; i++)
{
rgb[1] = g[i];
float[] xyz = cs.toCIEXYZ(rgb);
float[] inv = cs.fromCIEXYZ(xyz);
System.out.println("Color "+toString(rgb)+" ==>
XYZ "+toString(xyz)+
" ==>
color "+toString(inv));
}
}

private static String toString(float[] color)
{
StringBuffer buffer = new StringBuffer();
for (int i=0; i<color.length; i++)
{
if (i > 0)
buffer.append(' ');
buffer.append(color[i]);
}
return buffer.toString();
}
}
---------- END SOURCE ----------
(Review ID: 165411)
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