utils.c

        pos = url_ftell(pb);
        pd->buf_size = get_buffer(pb, buf, PROBE_BUF_SIZE);
        url_fseek(pb, pos, SEEK_SET);
        fmt = av_probe_image_format(pd);
    }
    if (!fmt)
        return AVERROR_NOFMT;
    ret = fmt->img_read(pb, alloc_cb, opaque);
    return ret;
}

/**
 * Write an image to a stream.
 * @param pb byte stream for the image output
 * @param fmt image format
 * @param img image data and informations
 */
int av_write_image(ByteIOContext *pb, AVImageFormat *fmt, AVImageInfo *img)
{
    return fmt->img_write(pb, img);
}