/*******************************************************************************
* Copyright (c) 2004, 2015 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.ui.internal.themes;
import java.util.Hashtable;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExecutableExtension;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.ui.themes.ColorUtil;
import org.eclipse.ui.themes.IColorFactory;
/**
* A <code>IColorFactory</code> that may be used to select a colour with
* a higher contrast. The colors to blend are specified as per method
* number two in {@link org.eclipse.core.runtime.IExecutableExtension}.
* <p>
* Example usage:
* <br/>
* <code>
* <colorDefinition
* label="Red/Blue Contrast"
* id="example.redblueblend">
* <colorFactory
* plugin="org.eclipse.ui"
* class="org.eclipse.ui.internal.themes.RGBContrastFactory">
* <parameter name="foreground" value="0,0,0" />
* <parameter name="background1" value="COLOR_RED" />
* <parameter name="background2" value="COLOR_BLUE" />
* </colorFactory>
* </colorDefinition>
* </code>
* </p>
*
* <p>
* This will select whichever of Red or Blue has a higher contrst with black.
* The color values may be specified as RGB triples or as SWT constants.
* </p>
*
* @see org.eclipse.swt.SWT
* @since 3.0
*/
public class RGBContrastFactory implements IColorFactory, IExecutableExtension {
private String fg, bg1, bg2;
/**
* Returns the intensity of an RGB component using the
* sRGB gamma function.
*
* @param val Value to convert.
* @return Light intensity of the component.
*/
double voltage_to_intensity_srgb(double val) {
/* Handle invalid values before doing a gamma transform. */
if (val < 0.0) {
return 0.0;
}
if (val > 1.0) {
return 1.0;
}
if (val <= 0.04045) {
return val / 12.92;
}
return Math.pow((val + 0.055) / 1.055, 2.4);
}
/**
* Returns a measure of the lightness in the perceptual colourspace
* IPT.
*
* @param color The colour in sRGB
* @return Lightness in IPT space.
*/
double lightness(RGB color) {
double r = voltage_to_intensity_srgb(color.red / 255.0);
double g = voltage_to_intensity_srgb(color.green / 255.0);
double b = voltage_to_intensity_srgb(color.blue / 255.0);
double l = (0.3139 * r) + (0.6395 * g) + (0.0466 * b);
double m = (0.1516 * r) + (0.7482 * g) + (0.1000 * b);
double s = (0.0177 * r) + (0.1095 * g) + (0.8729 * b);
double lp, mp, sp;
if (l < 0.0) {
lp = -Math.pow(-l, 0.43);
} else {
lp = Math.pow(l, 0.43);
}
if (m < 0.0) {
mp = -Math.pow(-m, 0.43);
} else {
mp = Math.pow(m, 0.43);
}
if (s < 0.0) {
sp = -Math.pow(-s, 0.43);
} else {
sp = Math.pow(s, 0.43);
}
return (0.4000 * lp) + (0.4000 * mp) + (0.2000 * sp);
}
@Override
public RGB createColor() {
/**
* Determine which pair has a higher contrast by selecting
* the colour with the furthest distance in lightness.
*/
RGB cfg, cbg1, cbg2;
if (fg != null) {
cfg = ColorUtil.getColorValue(fg);
} else {
cfg = new RGB(255, 255, 255);
}
if (bg1 != null) {
cbg1 = ColorUtil.getColorValue(bg1);
} else {
cbg1 = new RGB(0, 0, 0);
}
if (bg2 != null) {
cbg2 = ColorUtil.getColorValue(bg2);
} else {
cbg2 = new RGB(0, 0, 0);
}
double lfg = lightness(cfg);
double lbg1 = lightness(cbg1);
double lbg2 = lightness(cbg2);
if (Math.abs(lbg1 - lfg) > Math.abs(lbg2 - lfg)) {
return cbg1;
} else {
return cbg2;
}
}
/**
* This executable extension requires parameters to be explicitly declared
* via the second method described in the <code>IExecutableExtension</code>
* documentation. This class expects that there will be three parameters,
* <code>foreground</code>, <code>background1</code> and
* <code>background2</code>, that describe the two colors to be blended.
* These values may either be RGB triples or SWT constants.
*
* @see org.eclipse.core.runtime.IExecutableExtension#setInitializationData(org.eclipse.core.runtime.IConfigurationElement, java.lang.String, java.lang.Object)
*/
@Override
public void setInitializationData(IConfigurationElement config,
String propertyName, Object data) throws CoreException {
if (data instanceof Hashtable) {
Hashtable table = (Hashtable) data;
fg = (String) table.get("foreground"); //$NON-NLS-1$
bg1 = (String) table.get("background1"); //$NON-NLS-1$
bg2 = (String) table.get("background2"); //$NON-NLS-1$
}
}
}