opencv部分函数

opencv画图函数源代码

位置

opencv3_4_2\opencv\sources\modules\imgproc\src\drawing.cpp

void fillConvexPoly( Mat& img, const Point* pts, int npts,
                     const Scalar& color, int line_type, int shift )
{
    CV_INSTRUMENT_REGION()

    if( !pts || npts <= 0 )
        return;

    if( line_type == CV_AA && img.depth() != CV_8U )
        line_type = 8;

    double buf[4];
    CV_Assert( 0 <= shift && shift <=  XY_SHIFT );
    scalarToRawData(color, buf, img.type(), 0);
    std::vector _pts(pts, pts + npts);
    FillConvexPoly( img, _pts.data(), npts, buf, line_type, shift );
}


void fillPoly( Mat& img, const Point** pts, const int* npts, int ncontours,
               const Scalar& color, int line_type,
               int shift, Point offset )
{
    CV_INSTRUMENT_REGION()

    if( line_type == CV_AA && img.depth() != CV_8U )
        line_type = 8;

    CV_Assert( pts && npts && ncontours >= 0 && 0 <= shift && shift <= XY_SHIFT );

    double buf[4];
    scalarToRawData(color, buf, img.type(), 0);

    std::vector edges;

    int i, total = 0;
    for( i = 0; i < ncontours; i++ )
        total += npts[i];

    edges.reserve( total + 1 );
    for (i = 0; i < ncontours; i++)
    {
        std::vector _pts(pts[i], pts[i] + npts[i]);
        CollectPolyEdges(img, _pts.data(), npts[i], edges, buf, line_type, shift, offset);
    }

    FillEdgeCollection(img, edges, buf);
}

CollectPolyEdges函数

/******** Arbitrary polygon **********/

static void
CollectPolyEdges( Mat& img, const Point2l* v, int count, std::vector& edges,
                  const void* color, int line_type, int shift, Point offset )
{
    int i, delta = offset.y + ((1 << shift) >> 1);
    Point2l pt0 = v[count-1], pt1;
    pt0.x = (pt0.x + offset.x) << (XY_SHIFT - shift);
    pt0.y = (pt0.y + delta) >> shift;

    edges.reserve( edges.size() + count );

    for( i = 0; i < count; i++, pt0 = pt1 )
    {
        Point2l t0, t1;
        PolyEdge edge;

        pt1 = v[i];
        pt1.x = (pt1.x + offset.x) << (XY_SHIFT - shift);
        pt1.y = (pt1.y + delta) >> shift;

        if( line_type < CV_AA )
        {
            t0.y = pt0.y; t1.y = pt1.y;
            t0.x = (pt0.x + (XY_ONE >> 1)) >> XY_SHIFT;
            t1.x = (pt1.x + (XY_ONE >> 1)) >> XY_SHIFT;
            Line( img, t0, t1, color, line_type );
        }
        else
        {
            t0.x = pt0.x; t1.x = pt1.x;
            t0.y = pt0.y << XY_SHIFT;
            t1.y = pt1.y << XY_SHIFT;
            LineAA( img, t0, t1, color );
        }

        if( pt0.y == pt1.y )
            continue;

        if( pt0.y < pt1.y )
        {
            edge.y0 = (int)(pt0.y);
            edge.y1 = (int)(pt1.y);
            edge.x = pt0.x;
        }
        else
        {
            edge.y0 = (int)(pt1.y);
            edge.y1 = (int)(pt0.y);
            edge.x = pt1.x;
        }
        edge.dx = (pt1.x - pt0.x) / (pt1.y - pt0.y);
        edges.push_back(edge);
    }
}

struct CmpEdges
{
    bool operator ()(const PolyEdge& e1, const PolyEdge& e2)
    {
        return e1.y0 - e2.y0 ? e1.y0 < e2.y0 :
            e1.x - e2.x ? e1.x < e2.x : e1.dx < e2.dx;
    }
};

FillEdgeCollection函数

/**************** helper macros and functions for sequence/contour processing ***********/

static void
FillEdgeCollection( Mat& img, std::vector& edges, const void* color )
{
    PolyEdge tmp;
    int i, y, total = (int)edges.size();
    Size size = img.size();
    PolyEdge* e;
    int y_max = INT_MIN, y_min = INT_MAX;
    int64 x_max = 0xFFFFFFFFFFFFFFFF, x_min = 0x7FFFFFFFFFFFFFFF;
    int pix_size = (int)img.elemSize();

    if( total < 2 )
        return;

    for( i = 0; i < total; i++ )
    {
        PolyEdge& e1 = edges[i];
        assert( e1.y0 < e1.y1 );
        // Determine x-coordinate of the end of the edge.
        // (This is not necessary x-coordinate of any vertex in the array.)
        int64 x1 = e1.x + (e1.y1 - e1.y0) * e1.dx;
        y_min = std::min( y_min, e1.y0 );
        y_max = std::max( y_max, e1.y1 );
        x_min = std::min( x_min, e1.x );
        x_max = std::max( x_max, e1.x );
        x_min = std::min( x_min, x1 );
        x_max = std::max( x_max, x1 );
    }

    if( y_max < 0 || y_min >= size.height || x_max < 0 || x_min >= ((int64)size.width<y0; y < y_max; y++ )
    {
        PolyEdge *last, *prelast, *keep_prelast;
        int sort_flag = 0;
        int draw = 0;
        int clipline = y < 0;

        prelast = &tmp;
        last = tmp.next;
        while( last || e->y0 == y )
        {
            if( last && last->y1 == y )
            {
                // exclude edge if y reaches its lower point
                prelast->next = last->next;
                last = last->next;
                continue;
            }
            keep_prelast = prelast;
            if( last && (e->y0 > y || last->x < e->x) )
            {
                // go to the next edge in active list
                prelast = last;
                last = last->next;
            }
            else if( i < total )
            {
                // insert new edge into active list if y reaches its upper point
                prelast->next = e;
                e->next = last;
                prelast = e;
                e = &edges[++i];
            }
            else
                break;

            if( draw )
            {
                if( !clipline )
                {
                    // convert x's from fixed-point to image coordinates
                    uchar *timg = img.ptr(y);
                    int x1, x2;

                    if (keep_prelast->x > prelast->x)
                    {
                        x1 = (int)((prelast->x + XY_ONE - 1) >> XY_SHIFT);
                        x2 = (int)(keep_prelast->x >> XY_SHIFT);
                    }
                    else
                    {
                        x1 = (int)((keep_prelast->x + XY_ONE - 1) >> XY_SHIFT);
                        x2 = (int)(prelast->x >> XY_SHIFT);
                    }

                    // clip and draw the line
                    if( x1 < size.width && x2 >= 0 )
                    {
                        if( x1 < 0 )
                            x1 = 0;
                        if( x2 >= size.width )
                            x2 = size.width - 1;
                        ICV_HLINE( timg, x1, x2, color, pix_size );
                    }
                }
                keep_prelast->x += keep_prelast->dx;
                prelast->x += prelast->dx;
            }
            draw ^= 1;
        }

        // sort edges (using bubble sort)
        keep_prelast = 0;

        do
        {
            prelast = &tmp;
            last = tmp.next;

            while( last != keep_prelast && last->next != 0 )
            {
                PolyEdge *te = last->next;

                // swap edges
                if( last->x > te->x )
                {
                    prelast->next = te;
                    last->next = te->next;
                    te->next = last;
                    prelast = te;
                    sort_flag = 1;
                }
                else
                {
                    prelast = last;
                    last = te;
                }
            }
            keep_prelast = prelast;
        }
        while( sort_flag && keep_prelast != tmp.next && keep_prelast != &tmp );
    }
}

参考链接

python根据多边形polygon生成掩膜图像问题cv2.fillPoly()和cv2.fillConvexPoly()_cv2 polygon_清梦枕星河~的博客-CSDN博客

目标是根据画的多边形生成掩膜（即白色区域）图像，生成的图像大小与原图大小保持一致，在对应位置生成掩膜。

处理方式：

1、把画的多边形的各顶点坐标读出，要的是在图像中的像素坐标

2、生成与原图大小一致的全为0或1的图用于后续使用

3、根据cv2库的fillPoly函数在全0或全1 图的对应多边形位置进行填充

4、输出填充后得到掩膜的图像cv2.imwrite

进一步，如果需要生成环状的，如下图

左图，传入大正方形和小正方形的顶点即可；右图，传入小中大三个正方形的顶点即可

其他网址

https://blog.csdn.net/u012505629/article/details/116192377?ops_request_misc=&request_id=&biz_id=102&utm_term=cv.CollectPolyEdges()&utm_medium=distribute.pc_search_result.none-task-blog-2~all~sobaiduweb~default-3-116192377.142^v74^insert_down38,201^v4^add_ask,239^v2^insert_chatgpt&spm=1018.2226.3001.4187