JavaCV透视校正
我转换了使用OpenCV和C ++实现的透视校正代码： https ： //opencv-code.com/tutorials/automatic-perspective-correction-for-quadrilateral-objects/
获取以Java实现的以下OpenCV代码：
public class project { static Point2f center; public static void main(String args[]) { System.loadLibrary(Core.NATIVE_LIBRARY_NAME); center = new Point2f(0,0); Mat src = new Mat(); src = Highgui.imread("image.jpg"); if(src == null) { System.out.println("Image not loaded"); System.exit(1); } Mat bw = new Mat(); Imgproc.cvtColor(src, bw, Imgproc.COLOR_BGR2GRAY); Imgproc.blur(bw, bw, new Size(3,3)); Imgproc.Canny(bw, bw, 100, 100, 3,true); Mat lines = new Mat(); int threshold = 70; int minLineSize = 30; int lineGap = 10; Imgproc.HoughLinesP(bw, lines, 1, Math.PI / 180, threshold, minLineSize, lineGap); for (int x = 0; x < lines.cols(); x++) { double[] vec = lines.get(0, x); double[] val = new double[4]; val[0] = 0; val[1] = ((float) vec[1] - vec[3]) / (vec[0] - vec[2]) * -vec[0] + vec[1]; val[2] = src.cols(); val[3] = ((float) vec[1] - vec[3]) / (vec[0] - vec[2]) * (src.cols() - vec[2]) + vec[3]; lines.put(0, x, val); } List corners = new ArrayList(); for (int i = 0; i < lines.cols(); i++) { for (int j = i+1; j = 0 && pt.y >= 0) corners.add(pt); } } List approx = new ArrayList(); List curve; MatOfPoint2f mat2f = new MatOfPoint2f(); for(int k=0;k<corners.size();++k) { Point2f rec = corners.get(k); Point p = new Point(rec.x,rec.y); mat2f.fromArray(p); } MatOfPoint2f mat2frec = new MatOfPoint2f(); Imgproc.approxPolyDP(mat2f, mat2frec, Imgproc.arcLength(mat2f, true) * 0.02,true); if (approx.size() != 4) { System.out.println("The object is not quadrilateral!"); } // Get mass center for (int i = 0; i < corners.size(); i++) { center.x = center.x + corners.get(i).x; center.y = center.y + corners.get(i).y; } center.x *= (1. / corners.size()); center.y *= (1. / corners.size()); sortCorners(corners, center); Mat dst = src.clone(); // Draw lines for (int i = 0; i < lines.cols(); i++) { double[] v = lines.get(0, i); Scalar cc = new Scalar(0,255,0,0); Core.line(dst, new Point(v[0], v[1]), new Point(v[2], v[3]), cc); } Scalar c1 = new Scalar(0,0,255,0); Scalar c2 = new Scalar(0,255,0,0); Scalar c3 = new Scalar(255,0,0,0); Scalar c4 = new Scalar(255,255,255,0); // Draw corner points Core.circle(dst, new Point(corners.get(0).x,corners.get(0).y), 3, c1, 2); Core.circle(dst, new Point(corners.get(1).x,corners.get(1).y), 3, c2, 2); Core.circle(dst, new Point(corners.get(2).x,corners.get(2).y), 3, c3, 2); Core.circle(dst, new Point(corners.get(3).x,corners.get(3).y), 3, c4, 2); Scalar c5 = new Scalar(0,255,255,0); // Draw mass center Core.circle(dst, new Point(center.x,center.y), 3, c5, 2); Mat quad = Mat.zeros(300, 220, CvType.CV_8UC3); List quad_pts = new ArrayList(); quad_pts.add(new Point2f(0, 0)); quad_pts.add(new Point2f(quad.cols(), 0)); quad_pts.add(new Point2f(quad.cols(), quad.rows())); quad_pts.add(new Point2f(0, quad.rows())); Mat transmtx = Imgproc.getPerspectiveTransform((Mat) corners, (Mat) quad_pts); Imgproc.warpPerspective(src, quad, transmtx, quad.size()); MatOfByte matOfByte = new MatOfByte(); Highgui.imencode(".jpg", dst, matOfByte); byte[] byteArray = matOfByte.toArray(); BufferedImage bufImage = null; try { InputStream in = new ByteArrayInputStream(byteArray); bufImage = ImageIO.read(in); File outputfile = new File("Image.jpg"); ImageIO.write(bufImage, "jpg", outputfile); } catch (Exception e) { e.printStackTrace(); } MatOfByte matOfByte2 = new MatOfByte(); Highgui.imencode(".jpg", dst, matOfByte2); byte[] byteArray2 = matOfByte2.toArray(); BufferedImage bufImage2 = null; try { InputStream in = new ByteArrayInputStream(byteArray2); bufImage2 = ImageIO.read(in); File outputfile2 = new File("Quadrilateral.jpg"); ImageIO.write(bufImage, "jpg", outputfile2); } catch (Exception e) { e.printStackTrace(); } } static Point2f computeIntersect(Mat es, Mat es2) { int size = (int) es.total() * es.channels(); float[] buff = new float[size]; es.get(0, 0, buff); int size1 = (int) es.total() * es.channels(); float[] buff1 = new float[size1]; es.get(0, 0, buff1); float x1=buff[0], y1 = buff[1], x2 = buff[2], y2 = buff[3]; float x3 = buff1[0], y3 = buff1[1], x4 = buff1[2], y4 = buff1[3]; float denom; float d; d = (Float) null; d = (float)((x1 - x2) * (y3 - y4)) - ((y1 - y2) * (x3 - x4)); if (d != (Float) null) { Point2f pt = new Point2f(); pt.x = ((x1 * y2 - y1 * x2) * (x3 - x4) - (x1 - x2) * (x3 * y4 - y3 * x4)) / d; pt.y = ((x1 * y2 - y1 * x2) * (y3 - y4) - (y1 - y2) * (x3 * y4 - y3 * x4)) / d; return pt; } else return new Point2f(-1, -1); } static void sortCorners(List corners,Point2f center) { List top = null, bot = null; for (int i = 0; i < corners.size(); i++) { if (corners.get(i).y top.get(1).x ? top.get(1) : top.get(0); Point2f tr = top.get(0).x > top.get(1).x ? top.get(0) : top.get(1); Point2f bl = bot.get(0).x > bot.get(1).x ? bot.get(1) : bot.get(0); Point2f br = bot.get(0).x > bot.get(1).x ? bot.get(0) : bot.get(1); corners.clear(); corners.add(tl); corners.add(tr); corners.add(br); corners.add(bl); } } 我无法将List 转换为MatOfPoint2f。 因此，arcLength（..）函数不起作用，代码似乎不起作用。 我希望有人可以提供帮助。
这是我在我的项目中使用的实现的一部分。我已经使用我开发的算法确切的角点，但其余部分在此代码中给出。不要使用point2fs。 使用点数组，然后将它们转换为matofpoint2fs。
包含Imshow的jarfile可以从这里下载。它可以在任何时候测试你的o / p非常有效。 将此软件包添加到您的程序： https ： //github.com/master-atul/ImShow-Java-OpenCV
有关approxpolydp的详细信息： http ：//docs.opencv.org/java/org/opencv/imgproc/Imgproc.html#approxPolyDP%28org.opencv.core.MatOfPoint2f,org.opencv.core.MatOfPoint2f,double,boolean%29
你不必使用arclength。 只需给出epsilon的近似值，具体取决于输入的清晰度。（如2.0或3.0 ..）
（sort是用于对角进行排序的函数）。
int a[][],imgarr[][]; Point p[]; BufferedImage img; int w,h; void sort() { int x = (a[0][0] + a[1][0] + a[2][0] + a[3][0])/4; int y = (a[0][1] + a[1][1] + a[2][1] + a[3][1])/4; int j = 0; int order[] = new int[4]; double tans[] = new double[4]; double tans1[] = new double[4]; int tmpar[][] = new int[4][2]; p = new Point[4]; for(int i = 0;i<4;i++) { tans1[i] = tans[i] = Math.atan2(a[i][1] - y , a[i][0] - x);//finding angles for sorting corners } Arrays.sort(tans1); for(int i = 0;i<2;i++) { double temp = tans1[i]; tans1[i]= tans1[3-i]; tans1[3-i] = temp; } for(int i=0;i<4;i++) { for(j = 0;j<4;j++) { if(tans1[i]==tans[j]) break; } order[i] = j; } for(int i = 0;i<4;i++) { for(j=0;j<2;j++) { tmpar[i][j] = a[i][j]; } } for(int i = 0;i<4;i++) { for(j = 0;j<2;j++) { a[i][j] = tmpar[order[i]][j]; } } p[0] = new Point(a[0][1],a[0][0]); p[1] = new Point(a[1][1],a[1][0]); p[2] = new Point(a[2][1],a[2][0]); p[3] = new Point(a[3][1],a[3][0]); } void transform() throws Exception { Point farray[] = new Point[4]; try { img = ImageIO.read(new File("C:/Users/Documents/a.jpg")); } catch(Exception r) { System.out.println("no file"); } PixelGrabber pg; if(img==null) { return; } w = img.getWidth(); h = img.getHeight(); imgarr = new int[h][w]; try { for(int i = 0; i < h ; i++) { pg = new PixelGrabber(img,0,i,w,1,imgarr[i],0,w); pg.grabPixels(); } changeto256(); } catch(Exception e) { System.out.println("here "+e); } int m=0; byte array[] = new byte[w*h]; int iar[] = new int[w*h]; for(int i = 0 ; i < h ; i++) { for(int j = 0 ; j < w ; j++) { array[m++]= (byte)imgarr[i][j]; } } farray[3] = new Point(0,0); farray[0] = new Point(w,0); farray[1] = new Point(w,h); farray[2] = new Point(0,h); Mat mat = new Mat(h,w, CvType.CV_8U); mat.put(0, 0, array); Imshow is = new Imshow("try"); MatOfPoint2f quad = new MatOfPoint2f(p); MatOfPoint2f rect = new MatOfPoint2f(farray); Mat transmtx = Imgproc.getPerspectiveTransform(quad,rect); Mat output = new Mat(w,h,CvType.CV_8U); Imgproc.warpPerspective(mat, output, transmtx, new size(w,h),Imgproc.INTER_CUBIC); is.showImage(output); MatOfByte matOfByte = new MatOfByte(); Highgui.imencode(".jpg", output, matOfByte); byte[] byteArray = matOfByte.toArray(); File f = new File("retrieve1.jpg"); BufferedImage img1 =null; InputStream in = new ByteArrayInputStream(byteArray); img1 = ImageIO.read(in); WritableRaster raster = (WritableRaster)img1.getData(); raster.setDataElements(0,0,byteArray); img1.setData(raster); try { ImageIO.write(img1,"jpg",f); } catch(Exception e) {} }