FFMPEG 图像拉伸缩放及数据格式转换

本文转载自http://blog.csdn.net/li_wen01/article/details/65445743

在做摄像头数据采集处理的时候，经常会遇到摄像头输入数据格式的不同，导致编码的时候需要再进行一次数据装换。在X264的编码中，是需要将YUV的Y,U,V 三个分量的数据独立出来。遇到一些YUV交叉分布的数据就比较的麻烦，需要自己设计算法对数据进行分离。但是在FFMPEG中，它就已经包含了图像格式转换的接口，同时它还带有图像拉伸缩放的功能。下面代码实现了任意数据格式的转换和任意尺寸的缩放。

 /*=============================================================================
 #     FileName: scaling_image.c
 #         Desc: an example of ffmpeg scale image
 #       Author: licaibiao
 #   LastChange: 2017-03-23
 =============================================================================*/

 #include
 #include

 int main(int argc, charchar **argv)
 {
     enum AVPixelFormat src_pix_fmt = AV_PIX_FMT_YUYV422;
     enum AVPixelFormat dst_pix_fmt = AV_PIX_FMT_YUV420P;
     struct SwsContext *sws_ctx;

     const charchar *dst_filename = NULL;
     const charchar *src_filename = NULL;
     const charchar *dst_size = NULL;
     const charchar *src_size = NULL;
     uint8_t *src_data[4];
     uint8_t *dst_data[4];
     int src_linesize[4];
     int dst_linesize[4];
     int src_bufsize;
     int dst_bufsize;
     int src_w ;
     int src_h ;
     int dst_w ;
     int dst_h ;
     int i;
     int ret;

     FILEFILE *src_file;
     FILEFILE *dst_file;

     if (argc != 5) {
         fprintf(stderr, "Usage: %s input_file input_size(w x h)  output_file  output_size(w x h)\n"
                 "API example program to show how to scale an image with libswscale.\n"
                 "This program generates a  pictures, rescales them to the given "
                 "output_size and saves them to an output file named output_file\n."
                 "\n", argv[0]);
         exit(1);
     }

     /*source file parse*/
     src_filename = argv[1];
     src_size     = argv[2];
     if (av_parse_video_size(&src_w, &src_h, src_size) < 0) {
         fprintf(stderr,
                 "Invalid size '%s', must be in the form WxH or a valid size abbreviation\n",
                 dst_size);
         exit(1);
     }
     src_file = fopen(src_filename, "rb");
     if (!src_file) {
         fprintf(stderr, "Could not open source file %s\n", dst_filename);
         exit(1);
     }

     /*destination file parse*/
     dst_filename = argv[3];
     dst_size     = argv[4];
     if (av_parse_video_size(&dst_w, &dst_h, dst_size) < 0) {
         fprintf(stderr,
                 "Invalid size '%s', must be in the form WxH or a valid size abbreviation\n",
                 dst_size);
         exit(1);
     }
     dst_file = fopen(dst_filename, "wb");
     if (!dst_file) {
         fprintf(stderr, "Could not open destination file %s\n", dst_filename);
         exit(1);
     }

     /* create scaling context */
     sws_ctx = sws_getContext(src_w, src_h, src_pix_fmt, dst_w, dst_h, dst_pix_fmt,
                              SWS_BILINEAR, NULL, NULL, NULL);
     if (!sws_ctx) {
         fprintf(stderr,
                 "Impossible to create scale context for the conversion "
                 "fmt:%s s:%dx%d -> fmt:%s s:%dx%d\n",
                 av_get_pix_fmt_name(src_pix_fmt), src_w, src_h,
                 av_get_pix_fmt_name(dst_pix_fmt), dst_w, dst_h);
         ret = AVERROR(EINVAL);
         goto end;
     }

     /* allocate source and destination image buffers */
     if ((ret = av_image_alloc(src_data, src_linesize, src_w, src_h, src_pix_fmt, 16)) < 0) {
         fprintf(stderr, "Could not allocate source image\n");
         goto end;
     }
     src_bufsize = ret;

     /* buffer is going to be written to rawvideo file, no alignment */
     if ((ret = av_image_alloc(dst_data, dst_linesize, dst_w, dst_h, dst_pix_fmt, 1)) < 0) {
         fprintf(stderr, "Could not allocate destination image\n");
         goto end;
     }
     dst_bufsize = ret;

     fread(src_data[0], 1, src_bufsize, src_file);
     sws_scale(sws_ctx, (const uint8_t * const*)src_data,  src_linesize, 0, src_h, dst_data, dst_linesize);

     fprintf(stderr, "Scaling succeeded. Play the output file with the command:\n"
            "ffplay -f rawvideo -pix_fmt %s -video_size %dx%d %s\n",
            av_get_pix_fmt_name(dst_pix_fmt), dst_w, dst_h, dst_filename);

     /* write scaled image to file */
     fwrite(dst_data[0], 1, dst_bufsize, dst_file);

 end:
     fclose(dst_file);
     fclose(src_file);
     av_freep(&src_data[0]);
     av_freep(&dst_data[0]);
     sws_freeContext(sws_ctx);
     return ret < 0;
 }

Mkaefile

 OUT_APP      = test
 INCLUDE_PATH = /usr/local/include/
 INCLUDE = -I$(INCLUDE_PATH)libavutil/ -I$(INCLUDE_PATH)libavdevice/ \
             -I$(INCLUDE_PATH)libavcodec/ -I$(INCLUDE_PATH)libswresample \
             -I$(INCLUDE_PATH)libavfilter/ -I$(INCLUDE_PATH)libavformat \
             -I$(INCLUDE_PATH)libswscale/

 FFMPEG_LIBS = -lavformat -lavutil -lavdevice -lavcodec -lswresample -lavfilter -lswscale
 SDL_LIBS    =
 LIBS        = $(FFMPEG_LIBS)$(SDL_LIBS)

 COMPILE_OPTS = $(INCLUDE)
 C            = c
 OBJ          = o
 C_COMPILER   = cc
 C_FLAGS      = $(COMPILE_OPTS) $(CPPFLAGS) $(CFLAGS)

 LINK         = cc -o
 LINK_OPTS    = -lz -lm  -lpthread
 LINK_OBJ     = read_device.o

 .$(C).$(OBJ):
     $(C_COMPILER) -c -g $(C_FLAGS) $<


 $(OUT_APP): $(LINK_OBJ)
     $(LINK)$@  $(LINK_OBJ)  $(LIBS) $(LINK_OPTS)

 clean:
         -rm -rf *.$(OBJ) $(OUT_APP) core *.core *~  *.jpeg

运行：

 licaibiao@ubuntu:~/test/FFMPEG/examples$ ./test yuyv_320_240 320x240 out640_480 640x480
 Scaling succeeded. Play the output file with the command:
 ffplay -f rawvideo -pix_fmt yuv420p -video_size 640x480 out640_480
 licaibiao@ubuntu:~/test/FFMPEG/examples$

    运行时输入的参数为：输入文件，,输入文件的尺寸，输出文件名，输出文件尺寸。

    需要注意的是： 输入文件格式要与程序中src_pix_fmt 设置一致，输出数据格式由dst_pix_fmt 设置。

原始输入数据yuyv_320_240

拉伸后的输出数据：out640_480

    博客显示的问题看上去输入与输出图像差不多大，实际图片输入是输出的1/4大小。