使用python在OpenCV中进行透视校正

问题描述：

我正在尝试对在所有4个方向上都倾斜的倾斜矩形(信用卡)进行透视校正.我可以找到它的四个角以及倾斜的相应角度，但是我找不到必须将其投影到的坐标的确切位置.我正在使用cv2.getPerspectiveTransform进行转换.

I am trying to do a perspective correction of a tilted rectangle ( a credit card), which is tilted in all the 4 directions. I could find its four corners and the respective angles of its tilt but I cannot find the exact location of the coordinates, where it has to be projected. I am using cv2.getPerspectiveTransform to do the transformation.

我具有实际卡片(非倾斜卡片)的长宽比，我想要这样的坐标以保持原始长宽比.我尝试使用边界矩形，但这会增加卡的大小.

I have the aspect ratio of the actual card (the non tilted one), I want such coordinates such that the original aspect ratio is preserved. I have tried using a bounding rectangle but this increases the size of the card.

任何帮助将不胜感激.

Any help would be appreciated.

答

这是您需要遵循的方式...

Here is the way you need to follow...

为简便起见，我将您的图片调整为较小的尺寸，

For easiness I have resized your image to smaller size,

计算源图像的四边形顶点，在这里我手动进行查找，可以选择边缘检测，轮廓线等.

  Q1=manual calculation;
  Q2=manual calculation;
  Q3=manual calculation;
  Q4=manual calculation;

通过保持宽高比来计算目标图像中的四边形顶点，在这里您可以从源的四边形顶点上方获取卡的宽度，并乘以宽高比来计算高度.

   // compute the size of the card by keeping aspect ratio.
    double ratio=1.6;
    double cardH=sqrt((Q3.x-Q2.x)*(Q3.x-Q2.x)+(Q3.y-Q2.y)*(Q3.y-Q2.y)); //Or you can give your own height
    double cardW=ratio*cardH;
    Rect R(Q1.x,Q1.y,cardW,cardH);

现在您已经获得了用于源和目标的四边形顶点，然后应用warpPerspective.

您可以参考下面的C ++代码，

You can refer below C++ code,

   //Compute quad point for edge
    Point Q1=Point2f(90,11);
    Point Q2=Point2f(596,135);
    Point Q3=Point2f(632,452);
    Point Q4=Point2f(90,513);

    // compute the size of the card by keeping aspect ratio.
    double ratio=1.6;
    double cardH=sqrt((Q3.x-Q2.x)*(Q3.x-Q2.x)+(Q3.y-Q2.y)*(Q3.y-Q2.y));//Or you can give your own height
    double cardW=ratio*cardH;
    Rect R(Q1.x,Q1.y,cardW,cardH);

    Point R1=Point2f(R.x,R.y);
    Point R2=Point2f(R.x+R.width,R.y);
    Point R3=Point2f(Point2f(R.x+R.width,R.y+R.height));
    Point R4=Point2f(Point2f(R.x,R.y+R.height));

    std::vector<Point2f> quad_pts;
    std::vector<Point2f> squre_pts;

    quad_pts.push_back(Q1);
    quad_pts.push_back(Q2);
    quad_pts.push_back(Q3);
    quad_pts.push_back(Q4);

    squre_pts.push_back(R1);
    squre_pts.push_back(R2);
    squre_pts.push_back(R3);
    squre_pts.push_back(R4);


    Mat transmtx = getPerspectiveTransform(quad_pts,squre_pts);
    int offsetSize=150;
    Mat transformed = Mat::zeros(R.height+offsetSize, R.width+offsetSize, CV_8UC3);
    warpPerspective(src, transformed, transmtx, transformed.size());

    //rectangle(src, R, Scalar(0,255,0),1,8,0);

    line(src,Q1,Q2, Scalar(0,0,255),1,CV_AA,0);
    line(src,Q2,Q3, Scalar(0,0,255),1,CV_AA,0);
    line(src,Q3,Q4, Scalar(0,0,255),1,CV_AA,0);
    line(src,Q4,Q1, Scalar(0,0,255),1,CV_AA,0);

    imshow("quadrilateral", transformed);
    imshow("src",src);
    waitKey();

使用python在OpenCV中进行透视校正

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