Brixomatic commented on a change in pull request #114:
URL: https://github.com/apache/commons-imaging/pull/114#discussion_r548922568
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File path: src/main/java/org/apache/commons/imaging/color/ColorConversions.java
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@@ -16,44 +16,46 @@
*/
package org.apache.commons.imaging.color;
+import java.awt.Color;
public final class ColorConversions {
- private static final double REF_X = 95.047; // Observer= 2°, Illuminant=
D65
+
+ // White reference
+ /** see:
https://en.wikipedia.org/wiki/CIELAB_color_space#From_CIEXYZ_to_CIELAB[10] */
+ private static final double REF_X = 95.047; // Observer= 2°, Illuminant=
D65
+
+ /** see:
https://en.wikipedia.org/wiki/CIELAB_color_space#From_CIEXYZ_to_CIELAB[10] */
private static final double REF_Y = 100.000;
+
+ /** see:
https://en.wikipedia.org/wiki/CIELAB_color_space#From_CIEXYZ_to_CIELAB[10] */
private static final double REF_Z = 108.883;
+ /** see:
https://en.wikipedia.org/wiki/CIELAB_color_space#From_CIEXYZ_to_CIELAB[10] */
+ private static final double XYZ_m = 7.787037; // match in slope. Note
commonly seen 7.787 gives worse results
+
+ /** see:
https://en.wikipedia.org/wiki/CIELAB_color_space#From_CIEXYZ_to_CIELAB[10] */
+ private static final double XYZ_t0 = 0.008856;
+
private ColorConversions() {
}
public static ColorCieLab convertXYZtoCIELab(final ColorXyz xyz) {
return convertXYZtoCIELab(xyz.X, xyz.Y, xyz.Z);
}
- public static ColorCieLab convertXYZtoCIELab(final double X, final double
Y,
- final double Z) {
+ public static ColorCieLab convertXYZtoCIELab(final double X, final double
Y, final double Z) {
- double var_X = X / REF_X; // REF_X = 95.047 Observer= 2°, Illuminant=
- // D65
+ double var_X = X / REF_X; // REF_X = 95.047 Observer= 2°, Illuminant=
D65
double var_Y = Y / REF_Y; // REF_Y = 100.000
double var_Z = Z / REF_Z; // REF_Z = 108.883
- if (var_X > 0.008856) {
- var_X = Math.pow(var_X, (1 / 3.0));
- } else {
- var_X = (7.787 * var_X) + (16 / 116.0);
- }
- if (var_Y > 0.008856) {
- var_Y = Math.pow(var_Y, 1 / 3.0);
- } else {
- var_Y = (7.787 * var_Y) + (16 / 116.0);
- }
- if (var_Z > 0.008856) {
- var_Z = Math.pow(var_Z, 1 / 3.0);
- } else {
- var_Z = (7.787 * var_Z) + (16 / 116.0);
- }
+ // Pivot XÝZ:
+ var_X = pivotXYZ(var_X);
+ var_Y = pivotXYZ(var_Y);
+ var_Z = pivotXYZ(var_Z);
Review comment:
avoids some copy/paste errors as well, in case there are changes
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