JavaCV 透视校正
Posted
技术标签:
【中文标题】JavaCV 透视校正【英文标题】：JavaCV Perspective Correction 【发布时间】：2014-02-05 08:09:18 【问题描述】：我在以下位置转换了使用 OpenCV 和 C++ 实现的透视校正代码： https://opencv-code.com/tutorials/automatic-perspective-correction-for-quadrilateral-objects/
获取以下用Java实现的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<Point2f> corners = new ArrayList<Point2f>();
for (int i = 0; i < lines.cols(); i++)
for (int j = i+1; j < lines.cols(); j++)
Mat m1 = null,m2 = null;
double[] d1 = lines.get(0,i);
double[] d2 = lines.get(0, j);
m1.put(0, i, d1);
m2.put(0, j, d2);
Point2f pt = computeIntersect(m1, m2);
if (pt.x >= 0 && pt.y >= 0)
corners.add(pt);
List<Point2f> approx = new ArrayList<Point2f>();
List<Point2f> 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<Point2f> quad_pts = new ArrayList<Point2f>();
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<Point2f> corners,Point2f center)
List<Point2f> top = null, bot = null;
for (int i = 0; i < corners.size(); i++)
if (corners.get(i).y < center.y)
top.add(corners.get(i));
else
bot.add(corners.get(i));
Point2f tl = top.get(0).x > 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);
我在将 List
【问题讨论】：
BufferedImage 无法解析为类型？？ 【参考方案1】：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获得了确切的角点，但其余部分在此代码中给出。不要使用 point2fs。使用点数组并将它们转换为 matofpoint2fs。
包含 Imshow 的 jarfile 可以从这里下载。它在任何时候测试你的 o/p 都非常有效。将此包添加到您的程序中：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
而且你不必使用弧长。只需根据输入的清晰度为 epsilon 提供一个近似值。（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)
【讨论】：
我得到这个“BufferedImage 无法解析为一种类型”？？以上是关于JavaCV 透视校正的主要内容，如果未能解决你的问题，请参考以下文章