Linuxc语言用标准io给一个bmp图片变成马赛克

以下是一个简单的示例代码，可以实现将一个BMP图片转换为马赛克：

#include <stdio.h>
#include <stdint.h>

#define MOSAIC_SIZE 8

int main(int argc, char *argv[]) {
    if (argc != 3) {
        printf("Usage: %s input.bmp output.bmp\n", argv[0]);
        return 1;
    }

    FILE *input_file = fopen(argv[1], "rb");
    if (!input_file) {
        printf("Failed to open input file: %s\n", argv[1]);
        return 1;
    }

    FILE *output_file = fopen(argv[2], "wb");
    if (!output_file) {
        printf("Failed to open output file: %s\n", argv[2]);
        fclose(input_file);
        return 1;
    }

    // 读取BMP文件头
    uint8_t header[54];
    if (fread(header, 1, sizeof(header), input_file) != sizeof(header)) {
        printf("Failed to read BMP header\n");
        fclose(input_file);
        fclose(output_file);
        return 1;
    }

    // 验证BMP文件格式
    if (header[0] != 'B' || header[1] != 'M') {
        printf("Invalid BMP format\n");
        fclose(input_file);
        fclose(output_file);
        return 1;
    }

    // 读取BMP图片数据
    uint32_t width = *(uint32_t *)(header + 18);
    uint32_t height = *(uint32_t *)(header + 22);
    uint16_t bpp = *(uint16_t *)(header + 28) / 8;

    uint8_t *image_data = (uint8_t *)malloc(width * height * bpp);
    if (!image_data) {
        printf("Failed to allocate memory\n");
        fclose(input_file);
        fclose(output_file);
        return 1;
    }

    if (fread(image_data, 1, width * height * bpp, input_file) != width * height * bpp) {
        printf("Failed to read BMP image data\n");
        free(image_data);
        fclose(input_file);
        fclose(output_file);
        return 1;
    }

    // 将BMP图片数据转换为马赛克
    uint32_t x, y;
    uint8_t *src, *dst;
    uint32_t mosaic_width = width / MOSAIC_SIZE;
    uint32_t mosaic_height = height / MOSAIC_SIZE;

    for (y = 0; y < mosaic_height; y++) {
        for (x = 0; x < mosaic_width; x++) {
            uint32_t i, j;
            uint32_t r = 0, g = 0, b = 0;

            for (j = 0; j < MOSAIC_SIZE; j++) {
                for (i = 0; i < MOSAIC_SIZE; i++) {
                    src = image_data + ((y * MOSAIC_SIZE + j) * width + x * MOSAIC_SIZE + i) * bpp;
                    r += src[2];
                    g += src[1];
                    b += src[0];
                }
            }

            dst = image_data + ((y * MOSAIC_SIZE) * width + x * MOSAIC_SIZE) * bpp;
            dst[2] = r / (MOSAIC_SIZE * MOSAIC_SIZE);
            dst[1] = g / (MOSAIC_SIZE * MOSAIC_SIZE);
            dst[0] = b / (MOSAIC_SIZE * MOSAIC_SIZE);

            for (j = 0; j < MOSAIC_SIZE; j++) {
                for (i = 0; i < MOSAIC_SIZE; i++) {
                    if (i == 0 && j == 0) {
                        continue;
                    }

                    dst = image_data + ((y * MOSAIC_SIZE + j) * width + x * MOSAIC_SIZE + i) * bpp;
                    dst[2] = dst[-bpp * MOSAIC_SIZE + 2];
                    dst[1] = dst[-bpp * MOSAIC_SIZE + 1];
                    dst[0] = dst[-bpp * MOSAIC_SIZE + 0];
                }
            }
        }
    }

    // 写入BMP文件头
    if (fwrite(header, 1, sizeof(header), output_file) != sizeof(header)) {
        printf("Failed to write BMP header\n");
        free(image_data);
        fclose(input_file);
        fclose(output_file);
        return 1;
    }

    // 写入马赛克数据
    if (fwrite(image_data, 1, width * height * bpp, output_file) != width * height * bpp) {
        printf("Failed to write BMP image data\n");
        free(image_data);
        fclose(input_file);
        fclose(output_file);
        return 1;
    }

    free(image_data);
    fclose(input_file);
    fclose(output_file);

    return 0;
}

该程序使用标准C库函数实现了将一个BMP图片转换为马赛克的功能。具体实现思路是将图片按照一定的分辨率划分为若干个小块，然后对每个小块取平均RGB值，最终将小块的颜色统一设置为该平均值。