opencv旋转图像（JavaOpenCV图像旋转）

图形旋转是以图像的中心为原点，旋转一定的角度，也就是将图像上的所有像素都旋转一个相同的角度。旋转后图像的的大小一般会改变，即可以把转出显示区域的图像截去，或者扩大图像范围来显示所有的图像。图像的旋转变换也可以用矩阵变换来表示。

函数说明：Imgproc.getRotationMatrix2D(Point center, double angle, double scale)

参数详解： Point center：表示旋转的中心点； double angle：表示旋转的角度； double scale：图像缩放因子；

代码案例

package com.what21.opencv01.demo05; import org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.core.Point; import org.opencv.imgcodecs.Imgcodecs; import org.opencv.imgproc.Imgproc; /** * 图像旋转 */ public class OpenCVRotate { static { System.loadLibrary(Core.NATIVE_LIBRARY_NAME); } public static void main(String[] args) { Mat src = Imgcodecs.imread("D:/1.jpg"); Mat dst = src.clone(); //复制矩阵进入dst Point center = new Point(src.width() / 2.0, src.height() / 2.0); Mat affineTrans = Imgproc.getRotationMatrix2D(center, 33.0, 1.0); Imgproc.warpAffine(src, dst, affineTrans, dst.size(), Imgproc.INTER_NEAREST); Imgcodecs.imwrite("D:/1$1.jpg", dst); affineTrans = Imgproc.getRotationMatrix2D(center, 110.0, 1.1); Imgproc.warpAffine(src, dst, affineTrans, dst.size(), Imgproc.INTER_NEAREST); Imgcodecs.imwrite("D:/1$2.jpg", dst); } }

1.jpg

1$1.jpg

1$2.jpg

透视变换（Perspective Transformation)是指利用透视中心、像点、目标点三点共线的条件，按透视旋转定律使承影面（透视面）绕迹线（透视轴）旋转某一角度，破坏原有的投影光线束，仍能保持承影面上投影几何图形不变的变换。

代码案例

package com.what21.opencv01.demo05; import org.opencv.core.Core; import org.opencv.core.CvType; import org.opencv.core.Mat; import org.opencv.core.Point; import org.opencv.imgcodecs.Imgcodecs; import org.opencv.imgproc.Imgproc; import org.opencv.utils.Converters; import java.util.List; /** * 透视变换 */ public class OpenCVPerspective { static { System.loadLibrary(Core.NATIVE_LIBRARY_NAME); } public static void main(String[] args) { Mat src = Imgcodecs.imread("D:/1.jpg"); //读取图像到矩阵中,取灰度图像 if (src.empty()) { return; } try { int xMargin, yMargin; int x0 = src.cols() / 4; int x1 = (src.cols() / 4) * 3; int y0 = src.cols() / 4; int y1 = (src.cols() / 4) * 3; Mat dst = new Mat(); List<Point> listSrcs = java.util.Arrays.asList(new Point(x0, y0), new Point(x0, y1), new Point(x1, y1), new Point(x1, y0)); Mat srcPoints = Converters.vector_Point_to_Mat(listSrcs, CvType.CV_32F); xMargin = src.cols() / 10; yMargin = src.rows() / 10; List<Point> listDsts = java.util.Arrays.asList(new Point(x0 xMargin, y0 yMargin), listSrcs.get(1), listSrcs.get(2), new Point(x1 - xMargin, y0 yMargin)); Mat dstPoints = Converters.vector_Point_to_Mat(listDsts, CvType.CV_32F); Mat perspectiveMmat = Imgproc.getPerspectiveTransform(srcPoints, dstPoints); Imgproc.warpPerspective(src, dst, perspectiveMmat, src.size(), Imgproc.INTER_LINEAR); Imgcodecs.imwrite("D:/1.dst1.jpg", dst); xMargin = src.cols() / 8; yMargin = src.cols() / 8; listDsts.set(0, listSrcs.get(0)); listDsts.set(1, listSrcs.get(1)); listDsts.set(2, new Point(x1 - xMargin, y1 - yMargin)); listDsts.set(3, new Point(x1 - xMargin, y0 - yMargin)); dstPoints = Converters.vector_Point_to_Mat(listDsts, CvType.CV_32F); perspectiveMmat = Imgproc.getPerspectiveTransform(srcPoints, dstPoints); Imgproc.warpPerspective(src, dst, perspectiveMmat, src.size(), Imgproc.INTER_LINEAR); Imgcodecs.imwrite("D:/1.dst2.jpg", dst); xMargin = src.cols() / 6; yMargin = src.cols() / 6; listDsts.set(0, new Point(x0 xMargin, y0 yMargin)); listDsts.set(1, listSrcs.get(1)); listDsts.set(2, new Point(x1 - xMargin, y1 - yMargin)); listDsts.set(3, listSrcs.get(3)); dstPoints = Converters.vector_Point_to_Mat(listDsts, CvType.CV_32F); perspectiveMmat = Imgproc.getPerspectiveTransform(srcPoints, dstPoints); Imgproc.warpPerspective(src, dst, perspectiveMmat, src.size(), Imgproc.INTER_LINEAR); Imgcodecs.imwrite("D:/1.dst3.jpg", dst); } catch (Exception e) { e.printStackTrace(); } } }

1.dst1.jpg

1.dst2.jpg

1.dst3.jpg