ffmpeg 进行帧的纯色检测代码

你可以使用 FFmpeg 库来进行帧的纯色检测。下面是一个示例代码，它使用 FFmpeg 的 C API 来实现纯色检测：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <libavutil/avutil.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>

#define FRAME_THRESHOLD 0.95  // 帧的纯色阈值

int is_frame_pure_color(uint8_t *data, int linesize, int width, int height) {
    int i, j;
    int r, g, b;
    int count = 0;
    int total_pixels = width * height;
    
    for (i = 0; i < height; i++) {
        for (j = 0; j < width; j++) {
            r = data[i * linesize + j * 3];
            g = data[i * linesize + j * 3 + 1];
            b = data[i * linesize + j * 3 + 2];
            
            if (r == g && g == b) {
                count++;
            }
        }
    }
    
    double ratio = (double)count / total_pixels;
    
    return ratio >= FRAME_THRESHOLD ? 1 : 0;
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Usage: %s input_file\n", argv[0]);
        return -1;
    }
    
    const char *input_file = argv[1];
    
    av_log_set_level(AV_LOG_ERROR);  // 设置日志级别为错误
    
    AVFormatContext *format_ctx = NULL;
    AVCodecContext *codec_ctx = NULL;
    AVCodec *codec = NULL;
    AVFrame *frame = NULL;
    AVPacket packet;
    struct SwsContext *sws_ctx = NULL;
    
    if (avformat_open_input(&format_ctx, input_file, NULL, NULL) != 0) {
        printf("Failed to open input file\n");
        return -1;
    }
    
    if (avformat_find_stream_info(format_ctx, NULL) < 0) {
        printf("Failed to find stream information\n");
        return -1;
    }
    
    int video_stream_index = -1;
    
    for (int i = 0; i < format_ctx->nb_streams; i++) {
        if (format_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            video_stream_index = i;
            break;
        }
    }
    
    if (video_stream_index == -1) {
        printf("Failed to find video stream\n");
        return -1;
    }
    
    codec = avcodec_find_decoder(format_ctx->streams[video_stream_index]->codecpar->codec_id);
    
    if (!codec) {
        printf("Failed to find decoder\n");
        return -1;
    }
    
    codec_ctx = avcodec_alloc_context3(codec);
    
    if (!codec_ctx) {
        printf("Failed to allocate codec context\n");
        return -1;
    }
    
    if (avcodec_parameters_to_context(codec_ctx, format_ctx->streams[video_stream_index]->codecpar) < 0) {
        printf("Failed to copy codec parameters to codec context\n");
        return -1;
    }
    
    if (avcodec_open2(codec_ctx, codec, NULL) < 0) {
        printf("Failed to open codec\n");
        return -1;
    }
    
    frame = av_frame_alloc();
    
    if (!frame) {
        printf("Failed to allocate frame\n");
        return -1;
    }
    
    sws_ctx = sws_getContext(codec_ctx->width, codec_ctx->height, codec_ctx->pix_fmt,
                             codec_ctx->width, codec_ctx->height, AV_PIX_FMT_RGB24,
                             0, NULL, NULL, NULL);
    
    if (!sws_ctx) {
        printf("Failed to initialize sws context\n");
        return -1;
    }
    
    int frame_count = 0;
    
    while (av_read_frame(format_ctx, &packet) >= 0) {
        if (packet.stream_index == video_stream_index) {
            if (avcodec_send_packet(codec_ctx, &packet) < 0) {
                printf("Failed to send packet for decoding\n");
                break;
            }
            
            while (avcodec_receive_frame(codec_ctx, frame) >= 0) {
                AVFrame *rgb_frame = av_frame_alloc();
                
                if (!rgb_frame) {
                    printf("Failed to allocate RGB frame\n");
                    break;
                }
                
                uint8_t *rgb_buffer = (uint8_t *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_RGB24,
                                                                                     codec_ctx->width,
                                                                                     codec_ctx->height,
                                                                                     1));
                av_image_fill_arrays(rgb_frame->data, rgb_frame->linesize, rgb_buffer,
                                     AV_PIX_FMT_RGB24, codec_ctx->width, codec_ctx->height, 1);
                
                sws_scale(sws_ctx, frame->data, frame->linesize, 0, codec_ctx->height,
                          rgb_frame->data, rgb_frame->linesize);
                
                int is_pure_color = is_frame_pure_color(rgb_frame->data[0], rgb_frame->linesize[0],
                                                        codec_ctx->width, codec_ctx->height);
                
                printf("Frame %d is %s\n", frame_count, is_pure_color ? "pure color" : "not pure color");
                
                av_frame_free(&rgb_frame);
                av_free(rgb_buffer);
                
                frame_count++;
            }
        }
        
        av_packet_unref(&packet);
    }
    
    av_frame_free(&frame);
    avcodec_close(codec_ctx);
    avformat_close_input(&format_ctx);
    
    return 0;
}

这段代码使用了 FFmpeg 的 C API 来读取视频帧，并将每一帧转换为 RGB 格式，然后进行纯色检测。你可以将视频文件路径作为命令行参数传递给程序来进行测试。程序会输出每一帧是否为纯色帧。

这只是一个简单的示例代码，你可以根据自己的需求进行修改和扩展。请确保已正确安装 FFmpeg 库，并在编译时链接相应的库文件。