离散余弦变化图像处理的c语言代码

以下是一个简单的离散余弦变换（DCT）的C语言代码示例，用于对一幅图像进行处理：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define PI 3.14159265358979323846

void dct(float *input, float *output, int size)
{
    int i, j, k;
    float c, dct_sum;
    float *tmp = (float*) malloc(size * sizeof(float));

    for (i = 0; i < size; i++) {
        dct_sum = 0;
        for (j = 0; j < size; j++) {
            c = j == 0 ? sqrt(1.0 / size) : sqrt(2.0 / size);
            dct_sum += c * input[j] * cos((2 * i + 1) * j * PI / (2 * size));
        }
        tmp[i] = dct_sum;
    }

    for (i = 0; i < size; i++) {
        dct_sum = 0;
        for (j = 0; j < size; j++) {
            c = j == 0 ? sqrt(1.0 / size) : sqrt(2.0 / size);
            dct_sum += c * tmp[j] * cos((2 * i + 1) * j * PI / (2 * size));
        }
        output[i] = dct_sum;
    }

    free(tmp);
}

int main()
{
    int i, j, k;
    int width = 8, height = 8;
    float input[8][8] = {
        { 139, 144, 149, 153, 155, 155, 155, 155 },
        { 144, 151, 153, 156, 159, 156, 156, 156 },
        { 150, 155, 160, 163, 158, 156, 156, 156 },
        { 159, 161, 162, 160, 160, 159, 159, 159 },
        { 159, 160, 161, 162, 162, 155, 155, 155 },
        { 161, 161, 161, 161, 160, 157, 157, 157 },
        { 162, 162, 161, 163, 162, 157, 157, 157 },
        { 162, 162, 161, 161, 163, 158, 158, 158 }
    };
    float output[8][8];

    for (i = 0; i < height; i++) {
        for (j = 0; j < width; j++) {
            printf("%6.1f ", input[i][j]);
        }
        printf("\n");
    }

    printf("\n");

    for (i = 0; i < height; i += 8) {
        for (j = 0; j < width; j += 8) {
            float block[8][8];
            for (k = 0; k < 8; k++) {
                for (l = 0; l < 8; l++) {
                    block[k][l] = input[i + k][j + l];
                }
            }
            dct(block, block, 8);
            for (k = 0; k < 8; k++) {
                for (l = 0; l < 8; l++) {
                    output[i + k][j + l] = block[k][l];
                }
            }
        }
    }

    for (i = 0; i < height; i++) {
        for (j = 0; j < width; j++) {
            printf("%6.1f ", output[i][j]);
        }
        printf("\n");
    }

    return 0;
}

这个代码示例使用了一个简单的8x8像素块的DCT变换。输入块被分成8x8的块，并对每个块执行DCT变换。输出是一个与输入图像大小相同的图像，其中每个像素都已被DCT变换。