yuv420sp_to_jpg C语言

下面是将yuv420sp格式的图像转换为jpeg格式的C语言代码：

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

void yuv420sp_to_jpg(unsigned char *yuv, int width, int height, char *filename) {
    
    struct jpeg_compress_struct cinfo;
    struct jpeg_error_mgr jerr;
    
    JSAMPROW row_pointer[1];
    int row_stride;
    
    FILE *outfile = fopen(filename, "wb");
    if (outfile == NULL) {
        fprintf(stderr, "Cannot open output file %s\n", filename);
        return;
    }
    
    cinfo.err = jpeg_std_error(&jerr);
    jpeg_create_compress(&cinfo);
    jpeg_stdio_dest(&cinfo, outfile);
    
    cinfo.image_width = width;
    cinfo.image_height = height;
    cinfo.input_components = 3;
    cinfo.in_color_space = JCS_YCbCr;

    jpeg_set_defaults(&cinfo);
    jpeg_set_quality(&cinfo, 90, TRUE);
    
    jpeg_start_compress(&cinfo, TRUE);

    row_stride = width * 3;
    JSAMPLE *rgb = (JSAMPLE *)malloc(row_stride);
    
    while (cinfo.next_scanline < cinfo.image_height) {
        int y, u, v;
        unsigned char *py, *pu, *pv;
        py = yuv + cinfo.next_scanline * width;
        pu = yuv + width * height + (cinfo.next_scanline >> 1) * width;
        pv = yuv + width * height * 5 / 4 + (cinfo.next_scanline >> 1) * width;
        for (int i = 0, j = 0; i < width; i += 2, j += 6) {
            y = py[i];
            u = pu[j] - 128;
            v = pv[j] - 128;
            rgb[i * 3] = (unsigned char)(y + 1.4075 * v);
            rgb[i * 3 + 1] = (unsigned char)(y - 0.3455 * u - 0.7169 * v);
            rgb[i * 3 + 2] = (unsigned char)(y + 1.779 * u);
            y = py[i + 1];
            rgb[(i + 1) * 3] = (unsigned char)(y + 1.4075 * v);
            rgb[(i + 1) * 3 + 1] = (unsigned char)(y - 0.3455 * u - 0.7169 * v);
            rgb[(i + 1) * 3 + 2] = (unsigned char)(y + 1.779 * u);
        }
        row_pointer[0] = rgb;
        jpeg_write_scanlines(&cinfo, row_pointer, 1);
    }

    free(rgb);
    jpeg_finish_compress(&cinfo);
    fclose(outfile);
    jpeg_destroy_compress(&cinfo);
}

其中，yuv是yuv420sp格式的图像数据，width和height分别是图像的宽和高，filename是要保存的jpeg文件名。该函数使用libjpeg库将yuv420sp格式的图像数据转换为jpeg格式的图像数据，并保存到指定的文件中。具体的转换过程是将yuv数据转换为rgb数据，然后使用libjpeg库进行压缩编码。