用C语言实现rgb转nv12

以下是一个示例代码实现，实现了RGB图像到NV12图像的转换：

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

typedef struct {
    unsigned char r, g, b;
} RGBPixel;

typedef struct {
    unsigned char y, u, v;
} YUVPixel;

// 将RGB图像转换为YUV420格式
void rgb_to_yuv(RGBPixel *rgb_image, YUVPixel *yuv_image, int width, int height) {
    int i, j;
    RGBPixel *rgb_pixel;
    YUVPixel *yuv_pixel;

    for (i = 0; i < height; i++) {
        for (j = 0; j < width; j++) {
            rgb_pixel = rgb_image + i * width + j;
            yuv_pixel = yuv_image + i * width + j;

            yuv_pixel->y = (unsigned char)(0.299 * rgb_pixel->r + 0.587 * rgb_pixel->g + 0.114 * rgb_pixel->b);
            yuv_pixel->u = (unsigned char)(-0.169 * rgb_pixel->r - 0.331 * rgb_pixel->g + 0.5 * rgb_pixel->b + 128);
            yuv_pixel->v = (unsigned char)(0.5 * rgb_pixel->r - 0.419 * rgb_pixel->g - 0.081 * rgb_pixel->b + 128);
        }
    }
}

// 将YUV420图像转换为NV12格式
void yuv420_to_nv12(YUVPixel *yuv_image, unsigned char *nv12_image, int width, int height) {
    int i, j;
    YUVPixel *yuv_pixel;
    unsigned char *y_plane, *uv_plane;

    // Y分量直接拷贝
    y_plane = nv12_image;
    for (i = 0; i < height; i++) {
        for (j = 0; j < width; j++) {
            y_plane[i * width + j] = (yuv_image[i * width + j].y);
        }
    }

    // UV分量按2x2块进行平均采样
    uv_plane = nv12_image + width * height;
    for (i = 0; i < height; i += 2) {
        for (j = 0; j < width; j += 2) {
            yuv_pixel = yuv_image + i * width + j;

            *uv_plane++ = (unsigned char)((yuv_pixel[0].u + yuv_pixel[1].u + yuv_pixel[width].u + yuv_pixel[width + 1].u) / 4);
            *uv_plane++ = (unsigned char)((yuv_pixel[0].v + yuv_pixel[1].v + yuv_pixel[width].v + yuv_pixel[width + 1].v) / 4);
        }
    }
}

int main() {
    FILE *fp_rgb, *fp_nv12;
    int width = 640, height = 480, size = width * height * 3;
    RGBPixel *rgb_image;
    YUVPixel *yuv_image;
    unsigned char *nv12_image;

    // 读取RGB图像数据
    fp_rgb = fopen("rgb_image.raw", "rb");
    rgb_image = (RGBPixel *)malloc(size);
    fread(rgb_image, 1, size, fp_rgb);
    fclose(fp_rgb);

    // 分配YUV420和NV12图像数据空间
    yuv_image = (YUVPixel *)malloc(width * height * sizeof(YUVPixel));
    nv12_image = (unsigned char *)malloc(width * height * 3 / 2);

    // RGB图像转YUV420图像
    rgb_to_yuv(rgb_image, yuv_image, width, height);

    // YUV420图像转NV12图像
    yuv420_to_nv12(yuv_image, nv12_image, width, height);

    // 输出NV12图像数据
    fp_nv12 = fopen("nv12_image.raw", "wb");
    fwrite(nv12_image, 1, width * height * 3 / 2, fp_nv12);
    fclose(fp_nv12);

    // 释放内存
    free(rgb_image);
    free(yuv_image);
    free(nv12_image);

    return 0;
}

其中，`RGBPixel`和`YUVPixel`分别表示RGB和YUV像素，`rgb_to_yuv()`函数用于将RGB图像转换为YUV420格式，`yuv420_to_nv12()`函数用于将YUV420图像转换为NV12格式，`main()`函数中读取RGB图像数据并调用两个函数进行转换，最终输出NV12图像数据。