不使用库，用C语言写一个实现yuv数据拉伸缩放功能的程序

好的，我可以为您提供帮助，以下是实现yuv数据拉伸缩放功能的C语言代码示例：

#include <stdio.h>
#include <stdlib.h>
 
void resize_yuv(unsigned char* input_yuv, int src_width, int src_height, unsigned char* output_yuv, int dst_width, int dst_height) {
    int x, y;
    unsigned char* in_y = input_yuv;
    unsigned char* in_u = input_yuv + src_width * src_height;
    unsigned char* in_v = input_yuv + src_width * src_height * 5 / 4;
    unsigned char* out_y = output_yuv;
    unsigned char* out_u = output_yuv + dst_width * dst_height;
    unsigned char* out_v = output_yuv + dst_width * dst_height * 5 / 4;
    int dx = (src_width << 10) / dst_width + 1;
    int dy = (src_height << 10) / dst_height + 1;
    for (y = 0; y < dst_height; y++) {
        int iy = (y * dy) >> 10;
        for (x = 0; x < dst_width; x++) {
            int ix = (x * dx) >> 10;
            *out_y++ = *(in_y + iy * src_width + ix);
            if ((y & 1) == 0 && (x & 1) == 0) {
                *out_u++ = *(in_u + (iy / 2) * (src_width / 2) + (ix / 2));
                *out_v++ = *(in_v + (iy / 2) * (src_width / 2) + (ix / 2));
            }
        }
    }
}

使用示例：

int main(int argc, char* argv[]) {
    FILE* fin = fopen("input.yuv", "rb");
    FILE* fout = fopen("output.yuv", "wb");
    int src_width = 640;
    int src_height = 480;
    int dst_width = 320;
    int dst_height = 240;
    int input_size = src_width * src_height * 3 / 2;
    int output_size = dst_width * dst_height * 3 / 2;
    unsigned char* input_yuv = (unsigned char*)malloc(input_size);
    unsigned char* output_yuv = (unsigned char*)malloc(output_size);
    fread(input_yuv, 1, input_size, fin);
    resize_yuv(input_yuv, src_width, src_height, output_yuv, dst_width, dst_height);
    fwrite(output_yuv, 1, output_size, fout);
    free(input_yuv);
    free(output_yuv);
    fclose(fin);
    fclose(fout);
    return 0;
}

其中，input.yuv 和 output.yuv 分别是输入和输出的 YUV 数据文件。要根据实际情况修改输入和输出文件名、图像的宽高等参数。