如何使用ffmpeg函数对图像进行比例(宽高比)处理？

#include <stdio.h>
#include <stdlib.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>

int main(int argc, char* argv[]) {
    AVFormatContext* formatCtx = NULL;
    AVCodecContext* codecCtx = NULL;
    AVCodec* codec = NULL;
    AVFrame* frame = NULL;
    AVPacket packet;
    struct SwsContext* swsCtx = NULL;
    
    if (argc < 4) {
        fprintf(stderr, "Usage: %s <input_file> <output_file> <new_width>:<new_height>\n", argv[0]);
        return -1;
    }
    
    const char* inputFile = argv[1];
    const char* outputFile = argv[2];
    int newWidth = atoi(strtok(argv[3], ":"));
    int newHeight = atoi(strtok(NULL, ":"));
    
    av_register_all();
    
    if (avformat_open_input(&formatCtx, inputFile, NULL, NULL) != 0) {
        fprintf(stderr, "Failed to open input file\n");
        return -1;
    }
    
    if (avformat_find_stream_info(formatCtx, NULL) < 0) {
        fprintf(stderr, "Failed to find stream information\n");
        return -1;
    }
    
    int videoStreamIndex = -1;
    
    for (int i = 0; i < formatCtx->nb_streams; i++) {
        if (formatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
            videoStreamIndex = i;
            break;
        }
    }
    
    if (videoStreamIndex == -1) {
        fprintf(stderr, "Failed to find video stream\n");
        return -1;
    }
    
    codecCtx = formatCtx->streams[videoStreamIndex]->codec;
    codec = avcodec_find_decoder(codecCtx->codec_id);
    
    if (codec == NULL) {
        fprintf(stderr, "Failed to find decoder\n");
        return -1;
    }
    
    if (avcodec_open2(codecCtx, codec, NULL) < 0) {
        fprintf(stderr, "Failed to open decoder\n");
        return -1;
    }
    
    frame = av_frame_alloc();
    
    swsCtx = sws_getContext(codecCtx->width, codecCtx->height, codecCtx->pix_fmt,
                            newWidth, newHeight, AV_PIX_FMT_RGB24,
                            SWS_BILINEAR, NULL, NULL, NULL);
    
    FILE* outputFilePtr = fopen(outputFile, "wb");
    if (outputFilePtr == NULL) {
        fprintf(stderr, "Failed to open output file\n");
        return -1;
    }
    
    while (av_read_frame(formatCtx, &packet) >= 0) {
        if (packet.stream_index == videoStreamIndex) {
            avcodec_decode_video2(codecCtx, frame, &frameFinished, &packet);
            
            if (frameFinished) {
                uint8_t* data[1];
                data[0] = (uint8_t*)malloc(newWidth * newHeight * 3);
                if (data[0] != NULL) {
                    int linesize[1] = { newWidth * 3 };
                    sws_scale(swsCtx, frame->data, frame->linesize, 0, codecCtx->height, data, linesize);
                    fwrite(data[0], 1, newWidth * newHeight * 3, outputFilePtr);
                    free(data[0]);
                }
            }
        }
        av_free_packet(&packet);
    }
    
    fclose(outputFilePtr);
    av_frame_free(&frame);
    avcodec_close(codecCtx);
    avformat_close_input(&formatCtx);
    
    return 0;
}