在RGB色彩空间进行亮度图像亮度调整的方法步骤：

1)计算像素在R、G、B三个分量上的平均值

2)对三个平均值分别乘以对应的亮度系数brightness，默认为1则表示亮度不变，大于1 表示亮度提高，小于1 表示亮度变暗

3)对每个像素值在R、G、B上的分量，首先减去第一步计算出来的平均值，然后再加上第二步的计算结果。

Pnew = Pold +(brightness -1 )*means

Pnew 处理之后的像素，Pold 处理之前的像素，brightness 亮度系数(取值范围为【0~3】)，means图像像素的平均值

代码如下：

package chapter4;

import java.awt.image.BufferedImage;

/**

* Created by LENOVO on 18-1-29.

*/

public class BrightFilter extends AbstractBufferedImageOp {

private float brightness = 1.2f;//定义亮度系数

public BrightFilter(){

//this(1.2f);

}

public BrightFilter(float brightness){

this.brightness = brightness;

}

public float getBrightness() {

return brightness;

}

public void setBrightness(float brightness) {

this.brightness = brightness;

}

public BufferedImage filter(BufferedImage src,BufferedImage dest){

int width = src.getWidth();

int height = src.getHeight();

if(dest == null){

dest = creatCompatibleDestImage(src,null);

}

int[] inpixels = new int[width*height];

int[] outpixels = new int[width*height];

getRGB(src,0,0,width,height,inpixels);

int index = 0;

int[] rgbmeans = new int[3];

double redSum = 0;double greenSum = 0;double blueSum = 0;

double total = width*height;

for(int row=0;row

int ta = 0,tr = 0,tg = 0,tb = 0;

for(int col=0;col

index = row*width+col;

ta = (inpixels[index] >> 24) & 0xff;

tr = (inpixels[index] >> 16) & 0xff;

tg = (inpixels[index] >> 8) & 0xff;

tb = inpixels[index] & 0xff;

redSum += tr;

greenSum += tg;

blueSum += tb;

}

}

//1、计算RGB各分量平均值

rgbmeans[0] = (int)(redSum/total);

rgbmeans[1] = (int)(greenSum/total);

rgbmeans[2] = (int)(blueSum/total);

for(int row=0;row

int ta = 0,tr = 0,tg = 0,tb = 0;

for(int col=0;col

index = row*width+col;

ta = (inpixels[index] >> 24) & 0xff;

tr = (inpixels[index] >> 16) & 0xff;

tg = (inpixels[index] >> 8) & 0xff;

tb = inpixels[index] & 0xff;

//2、减去平均值

tr -= rgbmeans[0];

tg -= rgbmeans[1];

tb -= rgbmeans[2];

//3、加上平均值乘以亮度系数的值

tr += rgbmeans[0]*brightness;

tg += rgbmeans[1]*brightness;

tb += rgbmeans[2]*brightness;

outpixels[index] = (ta << 24) | (clamp(tr) << 16 ) | (clamp(tg) << 8) | clamp(tb);

}

}

setRGB(dest,0,0,width,height,outpixels);

return dest;

}

public int clamp(int value){

return value>255 ? 255:((value<0) ? 0:value);

}

}

测试代码同上