int av_picture_pad(AVPicture *dst, const AVPicture *src, int height, int width,
                   enum PixelFormat pix_fmt, int padtop, int padbottom, int padleft, int padright,
            int *color)
{
    uint8_t *optr;
    int y_shift;
    int x_shift;
    int yheight;
    int i, y;

    if (pix_fmt < 0 || pix_fmt >= PIX_FMT_NB ||
        !is_yuv_planar(&pix_fmt_info[pix_fmt])) return -1;

    for (i = 0; i < 3; i++) {
        x_shift = i ? av_pix_fmt_descriptors[pix_fmt].log2_chroma_w : 0;
        y_shift = i ? av_pix_fmt_descriptors[pix_fmt].log2_chroma_h : 0;

        if (padtop || padleft) {
            memset(dst->data[i], color[i],
                dst->linesize[i] * (padtop >> y_shift) + (padleft >> x_shift));
        }

        if (padleft || padright) {
            optr = dst->data[i] + dst->linesize[i] * (padtop >> y_shift) +
                (dst->linesize[i] - (padright >> x_shift));
            yheight = (height - 1 - (padtop + padbottom)) >> y_shift;
            for (y = 0; y < yheight; y++) {
                memset(optr, color[i], (padleft + padright) >> x_shift);
                optr += dst->linesize[i];
            }
        }

        if (src) { /* first line */
            uint8_t *iptr = src->data[i];
            optr = dst->data[i] + dst->linesize[i] * (padtop >> y_shift) +
                    (padleft >> x_shift);
            memcpy(optr, iptr, (width - padleft - padright) >> x_shift);
            iptr += src->linesize[i];
            optr = dst->data[i] + dst->linesize[i] * (padtop >> y_shift) +
                (dst->linesize[i] - (padright >> x_shift));
            yheight = (height - 1 - (padtop + padbottom)) >> y_shift;
            for (y = 0; y < yheight; y++) {
                memset(optr, color[i], (padleft + padright) >> x_shift);
                memcpy(optr + ((padleft + padright) >> x_shift), iptr,
                       (width - padleft - padright) >> x_shift);
                iptr += src->linesize[i];
                optr += dst->linesize[i];
            }
        }

        if (padbottom || padright) {
            optr = dst->data[i] + dst->linesize[i] *
                ((height - padbottom) >> y_shift) - (padright >> x_shift);
            memset(optr, color[i],dst->linesize[i] *
                (padbottom >> y_shift) + (padright >> x_shift));
        }
    }
    return 0;
}