写一段linux下bmp转yuv420的C语言代码

以下是一段简单的 Linux 下 BMP 转 YUV420 的 C 语言代码：

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

#define BMP_HEADER_SIZE 54

void bmp_to_yuv420(char *bmp_file, char *yuv_file, int width, int height) {
    FILE *bmp_fp = fopen(bmp_file, "rb");
    if (bmp_fp == NULL) {
        printf("Failed to open BMP file.\n");
        return;
    }

    FILE *yuv_fp = fopen(yuv_file, "wb");
    if (yuv_fp == NULL) {
        printf("Failed to create YUV file.\n");
        fclose(bmp_fp);
        return;
    }

    // BMP header
    unsigned char bmp_header[BMP_HEADER_SIZE];
    fread(bmp_header, sizeof(unsigned char), BMP_HEADER_SIZE, bmp_fp);

    // Image data
    int image_size = width * height * 3;
    unsigned char *image_data = (unsigned char *)malloc(image_size * sizeof(unsigned char));
    fread(image_data, sizeof(unsigned char), image_size, bmp_fp);

    // YUV data
    int y_size = width * height;
    int u_size = y_size / 4;
    int v_size = y_size / 4;
    unsigned char *yuv_data = (unsigned char *)malloc((y_size + u_size + v_size) * sizeof(unsigned char));

    // Convert BMP to YUV
    int i, j, k, l;
    for (i = 0; i < height; i++) {
        for (j = 0; j < width; j++) {
            int index = i * width + j;
            int y_index = i * width + j;
            int u_index = (i / 2) * (width / 2) + (j / 2) + y_size;
            int v_index = (i / 2) * (width / 2) + (j / 2) + y_size + u_size;

            unsigned char r = image_data[index * 3];
            unsigned char g = image_data[index * 3 + 1];
            unsigned char b = image_data[index * 3 + 2];

            // Y component
            yuv_data[y_index] = (unsigned char)(0.299 * r + 0.587 * g + 0.114 * b);

            // U component
            if (i % 2 == 0 && j % 2 == 0) {
                int u_sum = 0;
                for (k = i; k < i + 2; k++) {
                    for (l = j; l < j + 2; l++) {
                        int u_index = (k / 2) * (width / 2) + (l / 2) + y_size;
                        u_sum += image_data[(k * width + l) * 3 + 1];
                    }
                }
                yuv_data[u_index] = (unsigned char)(u_sum / 4);
            }

            // V component
            if (i % 2 == 0 && j % 2 == 0) {
                int v_sum = 0;
                for (k = i; k < i + 2; k++) {
                    for (l = j; l < j + 2; l++) {
                        int v_index = (k / 2) * (width / 2) + (l / 2) + y_size + u_size;
                        v_sum += image_data[(k * width + l) * 3 + 2];
                    }
                }
                yuv_data[v_index] = (unsigned char)(v_sum / 4);
            }
        }
    }

    // Write YUV file
    fwrite(yuv_data, sizeof(unsigned char), y_size + u_size + v_size, yuv_fp);

    // Cleanup
    free(image_data);
    free(yuv_data);
    fclose(bmp_fp);
    fclose(yuv_fp);
}

int main() {
    bmp_to_yuv420("input.bmp", "output.yuv", 640, 480);
    return 0;
}

这段代码会将输入的 BMP 文件转换为 YUV420 格式，并将结果保存到指定的 YUV 文件中。需要注意的是，这段代码仅适用于 24 位真彩色 BMP 图像。如果要处理其他类型的 BMP 图像，需要对代码进行适当的修改。