灰度图像c语言sauvola算法返回阈值
时间: 2023-08-15 07:10:13 浏览: 54
Sauvola算法是一种自适应阈值处理算法,适用于灰度图像的二值化处理。其核心思想是根据图像局部区域的灰度值分布来确定一个自适应的阈值。
下面是一份C语言代码实现Sauvola算法返回阈值的示例:
```c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define MAX(x, y) ((x) > (y) ? (x) : (y))
#define MIN(x, y) ((x) < (y) ? (x) : (y))
// 计算局部方差
double calcLocalVariance(int* img, int width, int height, int x, int y, int w_size) {
double sum = 0, ssum = 0;
int count = 0;
for (int j = MAX(0, y - w_size); j < MIN(height, y + w_size + 1); j++) {
for (int i = MAX(0, x - w_size); i < MIN(width, x + w_size + 1); i++) {
sum += img[j * width + i];
ssum += img[j * width + i] * img[j * width + i];
count++;
}
}
double mean = sum / count;
double variance = ssum / count - mean * mean;
return variance;
}
// 计算阈值
double calcThreshold(int* img, int width, int height, int w_size, double k) {
double threshold = 0;
int count = 0;
for (int j = 0; j < height; j++) {
for (int i = 0; i < width; i++) {
double variance = calcLocalVariance(img, width, height, i, j, w_size);
double local_threshold = img[j * width + i] * (1 + k * (sqrt(variance) / 128 - 1));
threshold += local_threshold;
count++;
}
}
return threshold / count;
}
int main() {
// 读取灰度图像
FILE* fp = fopen("test.bmp", "rb");
if (!fp) {
fprintf(stderr, "Failed to open image file\n");
return -1;
}
fseek(fp, 10, SEEK_SET);
int offset = 0;
fread(&offset, 4, 1, fp);
fseek(fp, 18, SEEK_SET);
int width = 0, height = 0;
fread(&width, 4, 1, fp);
fread(&height, 4, 1, fp);
fseek(fp, offset, SEEK_SET);
int* img = (int*)malloc(width * height * sizeof(int));
for (int j = height - 1; j >= 0; j--) {
for (int i = 0; i < width; i++) {
unsigned char r, g, b;
fread(&b, 1, 1, fp);
fread(&g, 1, 1, fp);
fread(&r, 1, 1, fp);
img[j * width + i] = (int)(0.299 * r + 0.587 * g + 0.114 * b + 0.5);
}
}
fclose(fp);
// 计算阈值
double threshold = calcThreshold(img, width, height, 20, 0.5);
printf("Threshold: %lf\n", threshold);
free(img);
return 0;
}
```
需要注意的是,上述代码中读取了一个BMP格式的灰度图像,如果需要处理其他格式的图像,则需要根据实际情况进行修改。此外,Sauvola算法中有两个参数:局部窗口大小和k值,这里设置为20和0.5,可以根据实际情况进行调整。