/*
* Copyright (c) 1997 - 2016
* Actelion Pharmaceuticals Ltd.
* Gewerbestrasse 16
* CH-4123 Allschwil, Switzerland
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. Neither the name of the the copyright holder nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
package com.actelion.research.util;
import java.awt.Color;
public class ColorHelper {
private static final float[] PERCEIVED_BRIGHTNESS = { 0.299f, 0.587f, 0.114f };
// the desired perceived brightness difference between foreground color and background
private static final float MIN_CONTRAST_TO_BACKGROUND = 0.30f;
/**
* Creates an intermediate color between color c1 and color c2
* in the RGB color space.
* @param c1
* @param c2
* @param ratio 0.0 -> returns c1; 1.0 -> returns c2
* @return color in between c1 and c2
*/
public static Color intermediateColor(Color c1, Color c2, float ratio) {
return new Color((int)(c1.getRed()+ratio*(c2.getRed()-c1.getRed())),
(int)(c1.getGreen()+ratio*(c2.getGreen()-c1.getGreen())),
(int)(c1.getBlue()+ratio*(c2.getBlue()-c1.getBlue())));
}
/**
* Creates a new <code>Color</code> that is a brighter version of this
* <code>Color</code>. This is a copy of Color.brighter(), but lets you choose
* the factor.
* @param c the color to be brightened
* @param factor value < 1.0; Color.brighter() uses 0.7
* @return a new <code>Color</code> object that is
* a brighter version of this <code>Color</code>
* with the same {@code alpha} value.
*/
public static Color brighter(Color c, float factor) {
int r = c.getRed();
int g = c.getGreen();
int b = c.getBlue();
int alpha = c.getAlpha();
/* From 2D group:
* 1. black.brighter() should return grey
* 2. applying brighter to blue will always return blue, brighter
* 3. non pure color (non zero rgb) will eventually return white
*/
int i = (int)(1.0/(1.0-factor));
if ( r == 0 && g == 0 && b == 0) {
return new Color(i, i, i, alpha);
}
if ( r > 0 && r < i ) r = i;
if ( g > 0 && g < i ) g = i;
if ( b > 0 && b < i ) b = i;
return new Color(Math.min((int)(r/factor), 255),
Math.min((int)(g/factor), 255),
Math.min((int)(b/factor), 255),
alpha);
}
/**
* Creates a new <code>Color</code> that is a darker version of this
* <code>Color</code>. This is a copy of Color.darker(), but lets you choose
* the factor.
* @param c the color to be darkened
* @param factor value < 1.0; Color.darker() uses 0.7
* @return a new <code>Color</code> object that is
* a darker version of this <code>Color</code>
* with the same {@code alpha} value.
*/
public static Color darker(Color c, float factor) {
return new Color(Math.max((int)(c.getRed() *factor), 0),
Math.max((int)(c.getGreen()*factor), 0),
Math.max((int)(c.getBlue() *factor), 0),
c.getAlpha());
}
/**
* This is a color's perceived brightness by the human eye
* @param c
* @return brightness from 0.0 to 1.0
*/
public static float perceivedBrightness(Color c) {
return (c == null) ? 1.0f : (PERCEIVED_BRIGHTNESS[0]*c.getRed()
+PERCEIVED_BRIGHTNESS[1]*c.getGreen()
+PERCEIVED_BRIGHTNESS[2]*c.getBlue()) / 255f;
}
/**
* Creates a new color with the hue taken from color <code>c</code>, but adjusted
* in brightness to match the desired perceived brightness.
* @param c
* @param perceivedBrightness
* @return
*/
public static Color createColor(Color c, float perceivedBrightness) {
float[] cc = c.getRGBComponents(null);
float pb = perceivedBrightness(c);
if (pb == 0f)
return new Color(pb, pb, pb, cc[3]);
float f = perceivedBrightness / perceivedBrightness(c);
float surplusBrightness = 0f;
float sum = 0f;
for (int i=0; i<3; i++) {
cc[i] *= f;
if (cc[i] < 1f) {
sum += PERCEIVED_BRIGHTNESS[i];
}
else {
surplusBrightness += (cc[i] - 1f) * PERCEIVED_BRIGHTNESS[i];
cc[i] = 1f;
}
}
if (surplusBrightness != 0) {
float remainingBrightness = 0f;
for (int i=0; i<3; i++) {
if (cc[i] < 1f) {
cc[i] += surplusBrightness / sum;
if (cc[i] > 1f) {
remainingBrightness += (cc[i] - 1f) * PERCEIVED_BRIGHTNESS[i];
cc[i] = 1f;
}
}
}
if (remainingBrightness != 0f) {
for (int i=0; i<3; i++) {
if (cc[i] < 1f) {
cc[i] += remainingBrightness / PERCEIVED_BRIGHTNESS[i];
if (cc[i] > 1f) {
cc[i] = 1f;
}
}
}
}
}
return new Color(cc[0], cc[1], cc[2], cc[3]);
}
/**
* Based on the differences of hue and perceived brightness of foreground color
* <code>fg</code> and background color <code>bg</code>, this method checks and
* possibly adjusts the given foreground color <code>fg</code> such that its hue
* stays unchanged, but its brightness is adapted to make it better perceivable
* on the background.
* @param fg foreground color
* @param bg background color
// * @param minContrast the minimum desired contrast (0 to 0.5)
* @return unchanged or adjusted fg
*/
public static Color getContrastColor(Color fg, Color bg) {
float bgb = ColorHelper.perceivedBrightness(bg);
float fgb = ColorHelper.perceivedBrightness(fg);
float contrast = Math.abs(bgb - fgb);
if (contrast > MIN_CONTRAST_TO_BACKGROUND)
return fg;
float[] hsbBG = new float[3];
Color.RGBtoHSB(bg.getRed(), bg.getGreen(), bg.getBlue(), hsbBG);
float[] hsbFG = new float[3];
Color.RGBtoHSB(fg.getRed(), fg.getGreen(), fg.getBlue(), hsbFG);
double hueDif = Math.abs(hsbFG[0] - hsbBG[0]);
if (hueDif > 0.5)
hueDif = 1.0 - hueDif;
float saturationFactor = 1-Math.max(hsbFG[1], hsbBG[1]);
float brightnessFactor = Math.abs(fgb + bgb - 1);
float hueDifferenceFactor = (float)Math.cos(Math.PI*hueDif*3);
float neededContrast = MIN_CONTRAST_TO_BACKGROUND * Math.max(saturationFactor, Math.max(brightnessFactor, hueDifferenceFactor));
if (contrast > neededContrast)
return fg;
boolean darken = (fgb > bgb) ? (fgb + neededContrast > 1f) : (fgb - neededContrast > 0f);
return createColor(fg, darken ? bgb - neededContrast : bgb + neededContrast);
}
}
