我在android平台上使用openCV库。我已经成功地从图像中检测到最大的矩形,但是由于我的应用程序将用于扫描目的,因此我也希望具有透视图更改功能。
我知道如何应用PerspectiveTransform和warpPerspectiveTransform,但是为此,我将需要矩形的角作为源点。
鉴于我们拥有与Rect对象相关联的第一个角的坐标(左上角)和宽度/高度,这似乎很容易找到角,但是问题是,对于旋转的矩形(通常为boundingRect,但边不平行于轴),这些值是非常不同的。在这种情况下,它存储的值对应于另一个矩形,该矩形的边与轴平行并且覆盖旋转的矩形,这使我无法检测到实际矩形的角。
我也想对这两种算法从图像中检测出一张纸进行比较。
Canny边缘->最大轮廓->最大矩形->查找角点->视角变化
Canny边缘-> Hough线->线的交点->视角变化
我想问的是如果我们有一个Rect对象,如何获得该矩形的所有角?
提前致谢。
我很高兴回答我的问题!这很容易,但是当你刚开始的时候没有相关文档的时候就发生了。
我正在努力获取openCV的实现中未定义的通用矩形的角,因此几乎是不可能的。
我遵循stackoverflow上的标准代码进行最大的Square检测。使用roxCurve本身可以轻松找到拐角。
//将图像转换为黑白
Imgproc.cvtColor(imgSource, imgSource, Imgproc.COLOR_BGR2GRAY); //convert the image to black and white does (8 bit) Imgproc.Canny(imgSource, imgSource, 50, 50); //apply gaussian blur to smoothen lines of dots Imgproc.GaussianBlur(imgSource, imgSource, new org.opencv.core.Size(5, 5), 5); //find the contours List<MatOfPoint> contours = new ArrayList<MatOfPoint>(); Imgproc.findContours(imgSource, contours, new Mat(), Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE); double maxArea = -1; int maxAreaIdx = -1; Log.d("size",Integer.toString(contours.size())); MatOfPoint temp_contour = contours.get(0); //the largest is at the index 0 for starting point MatOfPoint2f approxCurve = new MatOfPoint2f(); MatOfPoint largest_contour = contours.get(0); //largest_contour.ge List<MatOfPoint> largest_contours = new ArrayList<MatOfPoint>(); //Imgproc.drawContours(imgSource,contours, -1, new Scalar(0, 255, 0), 1); for (int idx = 0; idx < contours.size(); idx++) { temp_contour = contours.get(idx); double contourarea = Imgproc.contourArea(temp_contour); //compare this contour to the previous largest contour found if (contourarea > maxArea) { //check if this contour is a square MatOfPoint2f new_mat = new MatOfPoint2f( temp_contour.toArray() ); int contourSize = (int)temp_contour.total(); MatOfPoint2f approxCurve_temp = new MatOfPoint2f(); Imgproc.approxPolyDP(new_mat, approxCurve_temp, contourSize*0.05, true); if (approxCurve_temp.total() == 4) { maxArea = contourarea; maxAreaIdx = idx; approxCurve=approxCurve_temp; largest_contour = temp_contour; } } } Imgproc.cvtColor(imgSource, imgSource, Imgproc.COLOR_BayerBG2RGB); sourceImage =Highgui.imread(Environment.getExternalStorageDirectory(). getAbsolutePath() +"/scan/p/1.jpg"); double[] temp_double; temp_double = approxCurve.get(0,0); Point p1 = new Point(temp_double[0], temp_double[1]); //Core.circle(imgSource,p1,55,new Scalar(0,0,255)); //Imgproc.warpAffine(sourceImage, dummy, rotImage,sourceImage.size()); temp_double = approxCurve.get(1,0); Point p2 = new Point(temp_double[0], temp_double[1]); // Core.circle(imgSource,p2,150,new Scalar(255,255,255)); temp_double = approxCurve.get(2,0); Point p3 = new Point(temp_double[0], temp_double[1]); //Core.circle(imgSource,p3,200,new Scalar(255,0,0)); temp_double = approxCurve.get(3,0); Point p4 = new Point(temp_double[0], temp_double[1]); // Core.circle(imgSource,p4,100,new Scalar(0,0,255)); List<Point> source = new ArrayList<Point>(); source.add(p1); source.add(p2); source.add(p3); source.add(p4); Mat startM = Converters.vector_Point2f_to_Mat(source); Mat result=warp(sourceImage,startM); return result;
透视变换的功能如下:
public Mat warp(Mat inputMat,Mat startM) { int resultWidth = 1000; int resultHeight = 1000; Mat outputMat = new Mat(resultWidth, resultHeight, CvType.CV_8UC4); Point ocvPOut1 = new Point(0, 0); Point ocvPOut2 = new Point(0, resultHeight); Point ocvPOut3 = new Point(resultWidth, resultHeight); Point ocvPOut4 = new Point(resultWidth, 0); List<Point> dest = new ArrayList<Point>(); dest.add(ocvPOut1); dest.add(ocvPOut2); dest.add(ocvPOut3); dest.add(ocvPOut4); Mat endM = Converters.vector_Point2f_to_Mat(dest); Mat perspectiveTransform = Imgproc.getPerspectiveTransform(startM, endM); Imgproc.warpPerspective(inputMat, outputMat, perspectiveTransform, new Size(resultWidth, resultHeight), Imgproc.INTER_CUBIC); return outputMat; }