用houghLines估计偏斜水平 [英] estimate the skew level with houghLines

问题描述

我想从图像中检测偏斜水平。我有以下代码：

  public void analyze（CvMat img）{
 
 rows = img .rows（）; 
 cols = img.cols（）; 
 //从rois创建边缘图
 CvMat edgeMap = cvCreateMat（rows，cols，CV_8UC1）; 
 
 cvCanny（img，edgeMap，100,400,3）; 
 
 //转换为hough 
 CvMemStorage storage = cvCreateMemStorage（0）; 
 lines = cvHoughLines2（edgeMap，storage，CV_HOUGH_PROBABILISTIC，1，
 
 
 EuclideanDistance euclideanDistance = new EuclideanDistance（）; 
 double maxDistance = Double.MIN_VALUE; 
 for（int i = 0; i< lines.total（）; ++ i）{
 Pointer line = cvGetSeqElem（lines，i）; 
 CvPoint pt1 = new CvPoint（line）.position （0）; 
 CvPoint pt2 = new CvPoint（line）.position（1）; 
 double distance = euclideanDistance.getDistance（pt1，pt2）; 
 double currentAngle = Math.atan2（pt2 .y（） -  pt1.y（），
 pt2.x（） -  pt1.x（））
 * 180 / Math.PI; 
 System.out.println（currentAngle） ; 
 if（距离> maxDistance）{
 
 skewAngle = currentAngle; 
 
} 
} 
  

我的测试图片是

我认为偏斜水平是-16度但我的c ode说，那是25 ...

for也打出平均角度25。这个我的hough参数错了吗？

//这里的编辑是来自houghLines的图纸

问候语

解决方案

首先，由于你有一个相当清晰的文字，我建议你在Canny和Hough之前使用扩张/侵蚀。你会在字母里面获得更多的积分，霍夫肯定会从中受益。

其次，你选择最佳角度作为两点之间的最大距离。一行。

  double distance = euclideanDistance.getDistance（pt1，pt2）; 
 ... 
 if（distance> maxDistance）{
 skewAngle = currentAngle; 
} 
  

这不起作用，因为实际上Hough可能检测到不相关的线，比任何文本行都长：

如果你向自己显示每一步所做的事情你会得到一个更好的算法 - 你在Canny之后得到的，Hough变换产生了什么线等等。 / p>

i want to detect the skew level from an image. I've the following code:

public void analyse(CvMat img) {

    rows = img.rows();
    cols = img.cols();
    // create edge-map from rois
    CvMat edgeMap = cvCreateMat(rows, cols, CV_8UC1);

    cvCanny(img, edgeMap, 100, 400, 3);

    // transform to hough
    CvMemStorage storage = cvCreateMemStorage(0);
    lines = cvHoughLines2(edgeMap, storage, CV_HOUGH_PROBABILISTIC, 1,


    EuclideanDistance euclideanDistance = new EuclideanDistance();
    double maxDistance = Double.MIN_VALUE;
    for (int i = 0; i < lines.total(); ++i) {
        Pointer line = cvGetSeqElem(lines, i);
        CvPoint pt1 = new CvPoint(line).position(0);
        CvPoint pt2 = new CvPoint(line).position(1);
        double distance = euclideanDistance.getDistance(pt1, pt2);
        double currentAngle = Math.atan2(pt2.y() - pt1.y(),
                pt2.x() - pt1.x())
                * 180 / Math.PI;
        System.out.println(currentAngle);
        if (distance > maxDistance) {

            skewAngle = currentAngle;

        }
    }

My test image is

I think the skew level is by -16 degree but my code says, that is by 25...

The for prints out a avg angle by 25,too. Thats wrong with my hough parameters?

//EDIT here is a drawing from the houghLines

greetings

解决方案

Firstly, since you've got a rather clear text, I suggest you used dilate/erode prior to Canny and Hough. You'll get much more points inside the letters, from which Hough will definitely benefit.

Secondly, you choose you "best angle" as a maximum distance between two points of a line.

double distance = euclideanDistance.getDistance(pt1, pt2);
...
if (distance > maxDistance) {
    skewAngle = currentAngle;
}

This will NOT work, because in fact Hough may detect an uncorrelated line, which is longer than any line of text:

You may come out with a better algorithm if you display to yourself every step that is made - what you get after Canny, what lines did Hough transform produce etc.

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