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Rotate cv::Mat using cv::warpAffine offsets destination image
下面的代码可以成功地旋转图像，但是它会切掉图像的角并且旋转方向错误!!
Mat cvImage = Highgui.imread("mnt/sdcard/canvasgrid.png");
int degrees = 20;
Point center = new Point(cvImage.cols()/2, cvImage.rows()/2);
Mat rotImage = Imgproc.getRotationMatrix2D(center, degrees, 1.0);
Mat dummy = cvWaterImage;
Imgproc.warpAffine(cvImage, dummy, rotImage, cvImage.size());
rotatedImage = dummy;
Highgui.imwrite("mnt/sdcard/imageRotate.png",rotatedImage);
PLUS 旋转图像的背景是黑色的，但我希望它是透明的。
我做错什么了吗？ 谢谢
编辑已解决
首先获取旋转图像的新宽度/高度
double radians = Math.toRadians(rotationAngle);
double sin = Math.abs(Math.sin(radians));
double cos = Math.abs(Math.cos(radians));
int newWidth = (int) (scaledImage.width() * cos + scaledImage.height() * sin);
int newHeight = (int) (scaledImage.width() * sin + scaledImage.height() * cos);
int[] newWidthHeight = {newWidth, newHeight};
//创建新尺寸的框 (newWidth/newHeight)
int pivotX = newWidthHeight[0]/2;
int pivotY = newWidthHeight[1]/2;
//旋转的水图像
org.opencv.core.Point center = new org.opencv.core.Point(pivotX, pivotY);
Size targetSize = new Size(newWidthHeight[0], newWidthHeight[1]);
//现在创建另一个垫子，以便我们可以将其用于映射
Mat targetMat = new Mat(targetSize, scaledImage.type());
int offsetX = (newWidthHeight[0] - scaledImage.width()) / 2;
int offsetY = (newWidthHeight[1] - scaledImage.height()) / 2;
//集中水印
Mat waterSubmat = targetMat.submat(offsetY, offsetY + scaledImage.height(), offsetX, offsetX + scaledImage.width());
scaledImage.copyTo(waterSubmat);
Mat rotImage = Imgproc.getRotationMatrix2D(center, waterMarkAngle, 1.0);
Mat resultMat = new Mat(); // CUBIC
Imgproc.warpAffine(targetMat, resultMat, rotImage, targetSize, Imgproc.INTER_LINEAR, Imgproc.BORDER_CONSTANT, colorScalar);
//你的 resultMat 看起来像这样 NOT CROPPED Image //顺便说一句..提供的链接和这个解决方案之间存在巨大差异