BrightnessContrastFilter.java
/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * 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.
*
* * Neither the name of 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 HOLDER 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 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.twelvemonkeys.image;
import java.awt.image.RGBImageFilter;
/**
* Adjusts the contrast and brightness of an image.
* <p>
* For brightness, the valid range is {@code -2.0,..,0.0,..,2.0}.
* A value of {@code 0.0} means no change.
* Negative values will make the pixels darker.
* Maximum negative value ({@code -2}) will make all filtered pixels black.
* Positive values will make the pixels brighter.
* Maximum positive value ({@code 2}) will make all filtered pixels white.
* </p>
* <p>
* For contrast, the valid range is {@code -1.0,..,0.0,..,1.0}.
* A value of {@code 0.0} means no change.
* Negative values will reduce contrast.
* Maximum negative value ({@code -1}) will make all filtered pixels grey
* (no contrast).
* Positive values will increase contrast.
* Maximum positive value ({@code 1}) will make all filtered pixels primary
* colors (either black, white, cyan, magenta, yellow, red, blue or green).
* </p>
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @author last modified by $Author: haku $
*
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/image/BrightnessContrastFilter.java#1 $
*/
// TODO: consider doing something similar to http://archives.java.sun.com/cgi-bin/wa?A2=ind0302&L=jai-interest&F=&S=&P=15947
public class BrightnessContrastFilter extends RGBImageFilter {
// TODO: Replace with RescaleOp?
// This filter can filter IndexColorModel, as it is does not depend on
// the pixels' location
{
canFilterIndexColorModel = true;
}
// Use a pre-calculated lookup table for performance
private final int[] LUT;
/**
* Creates a BrightnessContrastFilter with default values
* ({@code brightness=0.3, contrast=0.3}).
* <p>
* This will slightly increase both brightness and contrast.
* </p>
*/
public BrightnessContrastFilter() {
this(0.3f, 0.3f);
}
/**
* Creates a BrightnessContrastFilter with the given values for brightness
* and contrast.
* <p>
* For brightness, the valid range is {@code -2.0,..,0.0,..,2.0}.
* A value of {@code 0.0} means no change.
* Negative values will make the pixels darker.
* Maximum negative value ({@code -2}) will make all filtered pixels black.
* Positive values will make the pixels brighter.
* Maximum positive value ({@code 2}) will make all filtered pixels white.
* </p>
* <p>
* For contrast, the valid range is {@code -1.0,..,0.0,..,1.0}.
* A value of {@code 0.0} means no change.
* Negative values will reduce contrast.
* Maximum negative value ({@code -1}) will make all filtered pixels grey
* (no contrast).
* Positive values will increase contrast.
* Maximum positive value ({@code 1}) will make all filtered pixels primary
* colors (either black, white, cyan, magenta, yellow, red, blue or green).
* </p>
*
* @param pBrightness adjust the brightness of the image, in the range
* {@code -2.0,..,0.0,..,2.0}.
* @param pContrast adjust the contrast of the image, in the range
* {@code -1.0,..,0.0,..,1.0}.
*/
public BrightnessContrastFilter(float pBrightness, float pContrast) {
LUT = createLUT(pBrightness, pContrast);
}
private static int[] createLUT(float pBrightness, float pContrast) {
int[] lut = new int[256];
// Hmmm.. This approximates Photoshop values.. Not good though..
double contrast = pContrast > 0 ? Math.pow(pContrast, 7.0) * 127.0 : pContrast;
// Convert range [-1,..,0,..,1] -> [0,..,1,..,2]
double brightness = pBrightness + 1.0;
for (int i = 0; i < 256; i++) {
lut[i] = clamp((int) (127.5 * brightness + (i - 127) * (contrast + 1.0)));
}
// Special case, to ensure only primary colors for max contrast
if (pContrast == 1f) {
lut[127] = lut[126];
}
return lut;
}
private static int clamp(int i) {
if (i < 0) {
return 0;
}
if (i > 255) {
return 255;
}
return i;
}
/**
* Filters one pixel, adjusting brightness and contrast according to this
* filter.
*
* @param pX x
* @param pY y
* @param pARGB pixel value in default color space
*
* @return the filtered pixel value in the default color space
*/
public int filterRGB(int pX, int pY, int pARGB) {
// Get color components
int r = pARGB >> 16 & 0xFF;
int g = pARGB >> 8 & 0xFF;
int b = pARGB & 0xFF;
// Scale to new contrast
r = LUT[r];
g = LUT[g];
b = LUT[b];
// Return ARGB pixel, leave transparency as is
return (pARGB & 0xFF000000) | (r << 16) | (g << 8) | b;
}
}