jpg转nv12_jpeg改jpg

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代码主要用到了libyuv库和libjpeg库。

编译：

g++ demo.cpp -lyuv -ljpeg -o demo

ubuntu下测试（需安装ffmpeg，width以及height按实际情况填写）： 

ffplay -i test.yuv -pixel_format nv12 -video_size widthxheight

demo： 

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

#define align_buffer_page_end(var, size)                                    \
    uint8_t* var##_mem =                                                    \
        reinterpret_cast<uint8_t*>(malloc(((size) + 4095 + 63) & ~4095));   \
    uint8_t* var = reinterpret_cast<uint8_t*>(                              \
        (intptr_t)(var##_mem + (((size) + 4095 + 63) & ~4095) - (size)) & ~63)

#define free_aligned_buffer_page_end(var)   \
    free(var##_mem);                        \
    var = 0

using namespace libyuv;

int main(int argc, char *argv[])
{
    int32_t width = 0, height = 0;

    FILE *dst;
    FILE *ori = fopen("test.jpg", "rb+");
    fseek(ori, 0, SEEK_END);
    uint32_t data_size = ftell(ori);
    fseek(ori, 0, SEEK_SET);
    uint8_t *data = (uint8_t *)calloc(1, data_size);
    fread(data, data_size, 1, ori);
    fclose(ori);

    int32_t ret = MJPGSize(data, data_size, &width, &height);
    int32_t half_width = (width + 1) / 2;
    int32_t half_height = (height + 1) / 2;

    align_buffer_page_end(dst_y, width * height);
    align_buffer_page_end(dst_uv, half_width * half_height * 2);

    ret = MJPGToNV12(data, data_size, dst_y, width, dst_uv, half_width * 2, width, height, width, height);
    if (0 == ret) {
        printf("change to nv12 success\n");
    } else {
        printf("change to nv12 failed\n");
        goto errChange;
    }

    dst = fopen("test.yuv", "wb+");
    fwrite(dst_y, width * height, 1, dst);
    fwrite(dst_uv, half_width * half_height * 2, 1, dst);
    fclose(dst);

errChange:
    free(data);
    free_aligned_buffer_page_end(dst_y);
    free_aligned_buffer_page_end(dst_uv);

    return 0;
}