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clahe_simple.cpp
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143 lines (142 loc) · 6.52 KB
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Mat claheGO(Mat src,int _step = 8)
{
Mat CLAHE_GO = src.clone();
int block = _step;//pblock
int width = src.cols;
int height= src.rows;
int width_block = width/block; //每个小格子的长和宽
int height_block = height/block;
//存储各个直方图
int tmp2[8*8][256] ={0};
float C2[8*8][256] = {0.0};
//分块
int total = width_block * height_block;
for (int i=0;i<block;i++)
{
for (int j=0;j<block;j++)
{
int start_x = i*width_block;
int end_x = start_x + width_block;
int start_y = j*height_block;
int end_y = start_y + height_block;
int num = i+block*j;
//遍历小块,计算直方图
for(int ii = start_x ; ii < end_x ; ii++)
{
for(int jj = start_y ; jj < end_y ; jj++)
{
int index =src.at<uchar>(jj,ii);
tmp2[num][index]++;
}
}
//裁剪和增加操作，也就是clahe中的cl部分
//这里的参数 对应《Gem》上面 fCliplimit = 4 , uiNrBins = 255
int average = width_block * height_block / 255;
//关于参数如何选择，需要进行讨论。不同的结果进行讨论
//关于全局的时候，这里的这个cl如何算，需要进行讨论
int LIMIT = 40 * average;
int steal = 0;
for(int k = 0 ; k < 256 ; k++)
{
if(tmp2[num][k] > LIMIT){
steal += tmp2[num][k] - LIMIT;
tmp2[num][k] = LIMIT;
}
}
int bonus = steal/256;
//hand out the steals averagely
for(int k = 0 ; k < 256 ; k++)
{
tmp2[num][k] += bonus;
}
//计算累积分布直方图
for(int k = 0 ; k < 256 ; k++)
{
if( k == 0)
C2[num][k] = 1.0f * tmp2[num][k] / total;
else
C2[num][k] = C2[num][k-1] + 1.0f * tmp2[num][k] / total;
}
}
}
//计算变换后的像素值
//根据像素点的位置，选择不同的计算方法
for(int i = 0 ; i < width; i++)
{
for(int j = 0 ; j < height; j++)
{
//four coners
if(i <= width_block/2 && j <= height_block/2)
{
int num = 0;
CLAHE_GO.at<uchar>(j,i) = (int)(C2[num][CLAHE_GO.at<uchar>(j,i)] * 255);
}else if(i <= width_block/2 && j >= ((block-1)*height_block + height_block/2)){
int num = block*(block-1);
CLAHE_GO.at<uchar>(j,i) = (int)(C2[num][CLAHE_GO.at<uchar>(j,i)] * 255);
}else if(i >= ((block-1)*width_block+width_block/2) && j <= height_block/2){
int num = block-1;
CLAHE_GO.at<uchar>(j,i) = (int)(C2[num][CLAHE_GO.at<uchar>(j,i)] * 255);
}else if(i >= ((block-1)*width_block+width_block/2) && j >= ((block-1)*height_block + height_block/2)){
int num = block*block-1;
CLAHE_GO.at<uchar>(j,i) = (int)(C2[num][CLAHE_GO.at<uchar>(j,i)] * 255);
}
//four edges except coners
else if( i <= width_block/2 )
{
//线性插值
int num_i = 0;
int num_j = (j - height_block/2)/height_block;
int num1 = num_j*block + num_i;
int num2 = num1 + block;
float p = (j - (num_j*height_block+height_block/2))/(1.0f*height_block);
float q = 1-p;
CLAHE_GO.at<uchar>(j,i) = (int)((q*C2[num1][CLAHE_GO.at<uchar>(j,i)]+ p*C2[num2][CLAHE_GO.at<uchar>(j,i)])* 255);
}else if( i >= ((block-1)*width_block+width_block/2)){
//线性插值
int num_i = block-1;
int num_j = (j - height_block/2)/height_block;
int num1 = num_j*block + num_i;
int num2 = num1 + block;
float p = (j - (num_j*height_block+height_block/2))/(1.0f*height_block);
float q = 1-p;
CLAHE_GO.at<uchar>(j,i) = (int)((q*C2[num1][CLAHE_GO.at<uchar>(j,i)]+ p*C2[num2][CLAHE_GO.at<uchar>(j,i)])* 255);
}else if( j <= height_block/2 ){
//线性插值
int num_i = (i - width_block/2)/width_block;
int num_j = 0;
int num1 = num_j*block + num_i;
int num2 = num1 + 1;
float p = (i - (num_i*width_block+width_block/2))/(1.0f*width_block);
float q = 1-p;
CLAHE_GO.at<uchar>(j,i) = (int)((q*C2[num1][CLAHE_GO.at<uchar>(j,i)]+ p*C2[num2][CLAHE_GO.at<uchar>(j,i)])* 255);
}else if( j >= ((block-1)*height_block + height_block/2) ){
//线性插值
int num_i = (i - width_block/2)/width_block;
int num_j = block-1;
int num1 = num_j*block + num_i;
int num2 = num1 + 1;
float p = (i - (num_i*width_block+width_block/2))/(1.0f*width_block);
float q = 1-p;
CLAHE_GO.at<uchar>(j,i) = (int)((q*C2[num1][CLAHE_GO.at<uchar>(j,i)]+ p*C2[num2][CLAHE_GO.at<uchar>(j,i)])* 255);
}
//双线性插值
else{
int num_i = (i - width_block/2)/width_block;
int num_j = (j - height_block/2)/height_block;
int num1 = num_j*block + num_i;
int num2 = num1 + 1;
int num3 = num1 + block;
int num4 = num2 + block;
float u = (i - (num_i*width_block+width_block/2))/(1.0f*width_block);
float v = (j - (num_j*height_block+height_block/2))/(1.0f*height_block);
CLAHE_GO.at<uchar>(j,i) = (int)((u*v*C2[num4][CLAHE_GO.at<uchar>(j,i)] +
(1-v)*(1-u)*C2[num1][CLAHE_GO.at<uchar>(j,i)] +
u*(1-v)*C2[num2][CLAHE_GO.at<uchar>(j,i)] +
v*(1-u)*C2[num3][CLAHE_GO.at<uchar>(j,i)]) * 255);
}
//smooth
CLAHE_GO.at<uchar>(j,i) = CLAHE_GO.at<uchar>(j,i) + (CLAHE_GO.at<uchar>(j,i) << 8) + (CLAHE_GO.at<uchar>(j,i) << 16);
}
}
return CLAHE_GO;
}