Android(安卓)OpenCV 旋转图像

使用opencv的摄像头预览图像是逆时针旋转90度的。

c++的方法多一点，我就想java也有直接的办法。参考API后看到这样一个方法，在Imgproc类下。

API说明：

getRotationMatrix2Dpublic static Mat getRotationMatrix2D(Point center,                      double angle,                      double scale)Calculates an affine matrix of 2D rotation.The function calculates the following matrix:alpha beta(1- alpha) * center.x - beta * center.y - beta alpha beta * center.x + (1- alpha) * center.ywherealpha = scale * cos angle, beta = scale * sin angleThe transformation maps the rotation center to itself. If this is not the target, adjust the shift.Parameters:center - Center of the rotation in the source image.angle - Rotation angle in degrees. Positive values mean counter-clockwise rotation (the coordinate origin is assumed to be the top-left corner).scale - Isotropic scale factor.

warpAffinepublic static void warpAffine(Mat src,              Mat dst,              Mat M,              Size dsize)Applies an affine transformation to an image.The function warpAffine transforms the source image using the specified matrix:dst(x,y) = src(M _11 x + M _12 y + M _13, M _21 x + M _22 y + M _23)when the flag WARP_INVERSE_MAP is set. Otherwise, the transformation is first inverted with "invertAffineTransform" and then put in the formula above instead of M. The function cannot operate in-place.Note: cvGetQuadrangleSubPix is similar to cvWarpAffine, but the outliers are extrapolated using replication border mode.Parameters:src - input image.dst - output image that has the size dsize and the same type as src.M - 2x 3 transformation matrix.dsize - size of the output image.

我在预览里添加转换函数：

@Overridepublic Mat onCameraFrame(CvCameraViewFrame inputFrame) {    // TODO Auto-generated method stub    Mat dst = new Mat();    Mat gray = inputFrame.gray();    Mat rotateMat = Imgproc.getRotationMatrix2D(new Point(gray.rows()/2,gray.cols()/2), 90, 1);    Imgproc.warpAffine(gray, dst, rotateMat, dst.size());    return dst;}

图像顺时针旋转90度

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