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图24 灰度图像
3．灰度图像处理
【例12】改善对比度。
算法说明：本例根据特定的输入输出灰度转换关系，增强了图像灰度，处理后图像的中等灰度值增大，图像变亮。
注意：本例中描述对比度改善的输入、输出灰度值对应关系的程序段为：
lev= 80; wid =100;
for (x=0;x<256;x+=1) {
lut[x]=255; }
for (x=lev;x<(lev+wid);x++) {
dm =((double)(x-lev)/(double)wid)*255f; lut [x] =(int)(dm); }
（1）在窗体上添加一个“对比度”命令按钮。 （2）双击“对比度”命令按钮，编辑代码如下：
private void button5_Click(object sender, EventArgs e) {
Color c = new Color();
Bitmap box1 = new Bitmap(pictureBox1.Image); Bitmap box2 = new Bitmap(pictureBox1.Image); int rr, x, m, lev, wid; int[] lut = new int[256];
int [,,]pic=new int[600,600,3]; double dm; lev = 80; .
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wid = 100;
for (x = 0; x < 256; x += 1) {
lut[x] = 255; }
for (x = lev; x < (lev + wid); x++) {
dm = ((double)(x - lev) / (double)wid) * 255f; lut[x] = (int)dm; }
for (int i = 0; i < pictureBox1.Image.Width - 1; i++) {
for (int j = 0; j < pictureBox1.Image.Height; j++) {
c = box1.GetPixel(i, j); pic[i, j, 0] = c.R; pic[i, j, 1] = c.G; pic[i, j, 2] = c.B; } }
for (int i = 0; i < pictureBox1.Image.Width - 1; i++) {
for (int j = 0; j < pictureBox1.Image.Height; j++) {
m = pic[i, j, 0]; rr=lut[m];
Color c1 = Color.FromArgb(rr, rr, rr); box2.SetPixel(i,j,c1); }
pictureBox2.Refresh(); pictureBox2.Image = box2; } }
（3）运行程序，运行结果如图25所示。
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图25 改善对比度
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C# - GDI+编程教程
