用C实现remosaic

以下是使用 C 语言实现的 remosaic 函数示例：

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

// 马赛克单元格大小
#define CELL_SIZE 2

void remosaic(unsigned char* image, int width, int height, const char* mosaic_pattern, unsigned char* remosaic_image) {
    int row, col, channel, cell_row, cell_col;
    int channels[4];
    int channel_vals[4];
    int offset[4][2] = {{0, 0}, {0, 1}, {1, 0}, {1, 1}};
    int R_offset, G_offset, B_offset;
    int mosaic_pattern_len = strlen(mosaic_pattern);

    // 根据马赛克模式设置颜色通道顺序
    if (strcmp(mosaic_pattern, "RGGB") == 0) {
        channels[0] = 0;
        channels[1] = 1;
        channels[2] = 2;
        channels[3] = 1;
        R_offset = 0;
        G_offset = 1;
        B_offset = 2;
    } else if (strcmp(mosaic_pattern, "GBRG") == 0) {
        channels[0] = 1;
        channels[1] = 0;
        channels[2] = 1;
        channels[3] = 2;
        R_offset = 2;
        G_offset = 1;
        B_offset = 0;
    } else if (strcmp(mosaic_pattern, "GRBG") == 0) {
        channels[0] = 1;
        channels[1] = 2;
        channels[2] = 0;
        channels[3] = 1;
        R_offset = 1;
        G_offset = 2;
        B_offset = 0;
    } else if (strcmp(mosaic_pattern, "BGGR") == 0) {
        channels[0] = 2;
        channels[1] = 1;
        channels[2] = 1;
        channels[3] = 0;
        R_offset = 2;
        G_offset = 0;
        B_offset = 1;
    } else {
        printf("Invalid mosaic pattern!\n");
        return;
    }

    // 逐个马赛克单元格处理
    for (row = 0; row < height; row += CELL_SIZE) {
        for (col = 0; col < width; col += CELL_SIZE) {
            // 获取该单元格的颜色通道值
            for (channel = 0; channel < 4; channel++) {
                cell_row = row + offset[channel][0];
                cell_col = col + offset[channel][1];
                channel_vals[channel] = image[(cell_row * width + cell_col) * 3 + channels[channel]];
            }
            // 按照马赛克模式重新排列颜色通道值
            for (channel = 0; channel < 4; channel++) {
                channel_vals[channel] = channel_vals[channels[channel]];
            }
            // 将颜色通道值反映到输出图像对应的像素中
            for (cell_row = row; cell_row < row + CELL_SIZE; cell_row++) {
                for (cell_col = col; cell_col < col + CELL_SIZE; cell_col++) {
                    remosaic_image[(cell_row * width + cell_col) * 3 + R_offset] = channel_vals[0];
                    remosaic_image[(cell_row * width + cell_col) * 3 + G_offset] = channel_vals[1];
                    remosaic_image[(cell_row * width + cell_col) * 3 + B_offset] = channel_vals[2];
                }
            }
        }
    }
}

int main() {
    // 读取原始图像
    FILE* fp = fopen("image.raw", "rb");
    int width = 640;
    int height = 480;
    unsigned char* image = (unsigned char*)malloc(width * height * 3);
    fread(image, 1, width * height * 3, fp);
    fclose(fp);

    // 执行 remosaic 操作
    char mosaic_pattern[] = "RGGB";
    unsigned char* remosaic_image = (unsigned char*)malloc(width * height * 3);
    remosaic(image, width, height, mosaic_pattern, remosaic_image);

    // 写入输出图像
    fp = fopen("remosaic.raw", "wb");
    fwrite(remosaic_image, 1, width * height * 3, fp);
    fclose(fp);

    free(image);
    free(remosaic_image);

    return 0;
}

该示例使用了一个 `remosaic` 函数来执行 remosaic 操作，其输入参数包括原始图像、图像宽度、图像高度、马赛克模式和输出图像。函数的实现方式与 Python 版本类似，也是逐个马赛克单元格处理，获取其颜色通道值并按照马赛克模式重新排列颜色通道值，最后将颜色通道值反映到输出图像对应的像素中。注意，在 C 语言中，需要通过指针来传递数组参数。