AVPicture中函数功能介绍

具体的请参考：http://ffmpeg.org/doxygen/trunk/group__lavc__picture.html

int avpicture_alloc (AVPicture *picture, enum AVPixelFormat pix_fmt, int width, int height) Allocate memory for the pixels of a picture and setup the AVPicture fields for it.  void avpicture_free (AVPicture *picture)//释放内存 Free a picture previously allocated by avpicture_alloc().  int avpicture_fill (AVPicture *picture, const uint8_t *ptr, enum AVPixelFormat pix_fmt, int width, int height)//把ptr和picture以pix_fmt格式关联起来，意思就是指针ptr=picture Setup the picture fields based on the specified image parameters and the provided image data buffer.  int avpicture_layout (const AVPicture *src, enum AVPixelFormat pix_fmt, int width, int height, unsigned char *dest, int dest_size) Copy pixel data from an AVPicture into a buffer.  int avpicture_get_size (enum AVPixelFormat pix_fmt, int width, int height)//解码后一帧图像的大小 Calculate the size in bytes that a picture of the given width and height would occupy if stored in the given picture format.  attribute_deprecated int avpicture_deinterlace (AVPicture *dst, const AVPicture *src, enum AVPixelFormat pix_fmt, int width, int height) deinterlace - if not supported return -1  void av_picture_copy (AVPicture *dst, const AVPicture *src, enum AVPixelFormat pix_fmt, int width, int height) Copy image src to dst.  int av_picture_crop (AVPicture *dst, const AVPicture *src, enum AVPixelFormat pix_fmt, int top_band, int left_band) Crop image top and left side.  int av_picture_pad