图像处理之调整亮度与饱和度
什么是亮度：
简单点说一幅图像的亮度属性是图像的RGB值的大小，RGB各个值越大亮度越高RGB
分量取值范围为0～255之间。调整图像亮度。
什么是饱和度：
饱和度是是指颜色的强度，调整饱和度可以修正过度曝光或者未充分曝光的图片。使
图像看上去更加自然。
基本思想：
通常在RGB色彩空间调整亮度与饱和度不是很直观，而HSL彩色空可以很直观表示出
每个像素的饱和度与亮度。所以首先读取图像的像素RGB值然后再转换到HSL空间得
到饱和度与亮度值，调整以后再从HSL空间转换到RGB空间的RGB值，对每个像素完
成这样的调整就完成图像的亮度与饱和度调整。关于RGB与HSL色彩空间的转换
看这里：http://en.wikipedia.org/wiki/HSL_color_space
程序效果：
滤镜源代码：
package com.gloomyfish.filter.study;
import java.awt.image.BufferedImage;
/**
* http://en.wikipedia.org/wiki/HSL_color_space
* @author gloomy fish
* @date 2012-09-26
*
*/
public class HSLFilter extends AbstractBufferedImageOp {
public final static double c1o60 = 1.0 / 60.0;
public final static double c1o255 = 1.0 / 255.0;
private double hue;
private double saturation;
private double lightness;
public HSLFilter() {
System.out.println("Hue Filter");
}
public double getHue() {
return hue;
}
public void setHue(double hue) {
while (hue < 0.0) {
this.hue += 360;
}
while (hue >= 360.0) {
this.hue -= 360;
}
}
public double getSaturation() {
return saturation;
}
public void setSaturation(double saturation) {
if((saturation >= -100.0) && (saturation <= 100.0)) {
this.saturation = saturation;
}
}
public double getLightness() {
return lightness;
}
public void setLightness(double lightness) {
if((lightness >= -100.0) && (lightness <= 100.0)) {
this.lightness = lightness;
}
}
@Override
public BufferedImage filter(BufferedImage src, BufferedImage dest) {
int width = src.getWidth();
int height = src.getHeight();
double sat = 127.0d * saturation / 100.0d;
double lum = 127.0d * lightness / 100.0d;
if ( dest == null )
dest = createCompatibleDestImage( src, null );
int[] inPixels = new int[width*height];
int[] outPixels = new int[width*height];
getRGB( src, 0, 0, width, height, inPixels );
double min, max, dif, sum;
double f1, f2;
int index = 0;
double h, s, l;
double v1, v2, v3, h1;
for(int row=0; row<height; row++) {
int ta = 0, tr = 0, tg = 0, tb = 0;
for(int col=0; col<width; col++) {
index = row * width + col;
ta = (inPixels[index] >> 24) & 0xff;
tr = (inPixels[index] >> 16) & 0xff;
tg = (inPixels[index] >> 8) & 0xff;
tb = inPixels[index] & 0xff;
// convert to HSL space
min = tr;
if (tg < min)
min = tg;
if (tb < min)
min = tb;
max = tr;
f1 = 0.0;
f2 = tg - tb;
if (tg > max) {
max = tg;
f1 = 120.0;
f2 = tb - tr;
}
if (tb > max) {
max = tb;
f1 = 240.0;
f2 = tr - tg;
}
dif = max - min;
sum = max + min;
l = 0.5 * sum;
if (dif == 0) {
h = 0.0;
s = 0.0;
}
else if(l < 127.5) {
s = 255.0 * dif / sum;
}
else {
s = 255.0 * dif / (510.0 - sum);
}
h = (f1 + 60.0 * f2 / dif);
if (h < 0.0) {
h += 360.0;
}
if (h >= 360.0) {
h -= 360.0;
}
// Apply transformation.
h = h + hue;
if( h >= 360.0) {
h = h - 360.0;
}
s = s + sat;
if( s < 0.0) {
s = 0.0;
}
if( s > 255.0) {
s = 255.0;
}
l = l + lum;
if( l < 0.0) {
l = 0.0;
}
if( l > 255.0) {
l = 255.0;
}
// conversion back to RGB space here!!
if (s == 0) {
tr = (int)l;
tg = (int)l;
tb = (int)l;
} else {
if (l < 127.5) {
v2 = c1o255 * l * (255 + s);
} else {
v2 = l + s - c1o255 * s * l;
}
v1 = 2 * l - v2;
v3 = v2 - v1;
h1 = h + 120.0;
if (h1 >= 360.0)
h1 -= 360.0;
if (h1 < 60.0) {
tr = (int)(v1 + v3 * h1 * c1o60);
}
else if (h1 < 180.0) {
tr = (int)v2;
}
else if (h1 < 240.0) {
tr = (int)(v1 + v3 * (4 - h1 * c1o60));
}
else {
tr = (int)v1;
}
h1 = h;
if (h1 < 60.0) {
tg = (int)(v1 + v3 * h1 * c1o60);
}
else if (h1 < 180.0) {
tg = (int)v2;
}
else if (h1 < 240.0) {
tg = (int)(v1 + v3 * (4 - h1 * c1o60));
}
else {
tg = (int)v1;
}
h1 = h - 120.0;
if (h1 < 0.0) {
h1 += 360.0;
}
if (h1 < 60.0) {
tb = (int)(v1 + v3 * h1 * c1o60);
}
else if (h1 < 180.0) {
tb = (int)v2;
}
else if (h1 < 240.0) {
tb = (int)(v1 + v3 * (4 - h1 * c1o60));
}
else {
tb = (int)v1;
}
}
outPixels[index] = (ta << 24) | (tr << 16) | (tg << 8) | tb;
}
}
setRGB( dest, 0, 0, width, height, outPixels );
return dest;
}
}
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