java - 在 Android 上的 OpenCV 中旋转 VideoCapture

Question

在 OpenCV 上使用 VideoCapture 类时如何旋转相机？ (Android 上的人脸检测示例)。我正在旋转 Canvas :

if (getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT)
{
    Matrix matrix = new Matrix();
    matrix.preTranslate(
    (canvas.getWidth() - bmp.getWidth()) / 2,
    (canvas.getHeight() - bmp.getHeight()) / 2);
    matrix.postRotate(270f, (canvas.getWidth()) / 2,
    (canvas.getHeight()) / 2);
    canvas.drawBitmap(bmp, matrix, null);
}

但来自相机的图像不旋转:人脸检测不工作。

相机从以下位置接收流:

protected Bitmap processFrame(VideoCapture capture) {

    capture.retrieve(mRgba, Highgui.CV_CAP_ANDROID_COLOR_FRAME_RGBA);

    capture.retrieve(mGray,
    Highgui.CV_CAP_ANDROID_GREY_FRAME);

更新我做了以下事情:

@Override
    protected Bitmap processFrame(VideoCapture capture) {

    if (getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) {
        Core.flip(mRgba.t(), mRgba, 0);
    }

    else {
    }
    capture.retrieve(mRgba, Highgui.CV_CAP_ANDROID_COLOR_FRAME_RGBA);
    capture.retrieve(mDetect_thread.mGray,
            Highgui.CV_CAP_ANDROID_GREY_FRAME);

但是不起作用。当我在 portret 方向(在 android 设备上)运行程序时 - 程序不启动当我在横向运行 rogram - 程序工作，但是当我旋转设备时，程序工作，但显示的图像不旋转

Answer 1

您的问题主要是 duplicate of this , 除了您正在寻找 Android 版本。它非常相似，但在这里，可以通过转置然后翻转图像来获得 90º 旋转:

# rotate 90º counter-clockwise
Core.flip(mRgba.t(), mRgba, 0); //mRgba.t() is the transpose

# rotate 90º clockwise
Core.flip(mRgba.t(), mRgba, 1);

对于其他旋转，您可以使用 warpAffine :

Point center = new Point(x,y);
double angle = 90;
double scale = 1.0;

Mat mapMatrix = Imgproc.getRotationMatrix2D(center, angle, scale);
Imgproc.warpAffine(srcMat, dstMat, mapMatrix, Imgproc.INTER_LINEAR);

编辑 - 更完整的示例如下:

    /** 
     * Image is first resized-to-fit the dst Mat and then rotated. 
     * mRgba is the source image, mIntermediateMat should have the same type.
     */
    private void rotationTutorial(){
        double ratio =  mRgba.height() / (double) mRgba.width();

        int rotatedHeight = mRgba.height();     
        int rotatedWidth  = (int) Math.round(mRgba.height() * ratio);

        Imgproc.resize(mRgba, mIntermediateMat, new Size(rotatedHeight, rotatedWidth));

        Core.flip(mIntermediateMat.t(), mIntermediateMat, 0);

        Mat ROI = mRgba.submat(0, mIntermediateMat.rows(), 0, mIntermediateMat.cols());

        mIntermediateMat.copyTo(ROI);       
    }


    /** 
     * Image is rotated - cropped-to-fit dst Mat.
     * 
     */
    private void rotationAffineTutorial(){
        // assuming source image's with and height are a pair value:
        int centerX = Math.round(mRgba.width()/2);
        int centerY = Math.round(mRgba.height()/2);

        Point center = new Point(centerY,centerX);
        double angle = 90;
        double scale = 1.0;

        double ratio =  mRgba.height() / (double) mRgba.width();

        int rotatedHeight = (int) Math.round(mRgba.height());       
        int rotatedWidth  = (int) Math.round(mRgba.height() * ratio);

        Mat mapMatrix = Imgproc.getRotationMatrix2D(center, angle, scale);

        Size rotatedSize = new Size(rotatedWidth, rotatedHeight);
        mIntermediateMat = new Mat(rotatedSize, mRgba.type());

        Imgproc.warpAffine(mRgba, mIntermediateMat, mapMatrix, mIntermediateMat.size(), Imgproc.INTER_LINEAR);

        Mat ROI = mRgba.submat(0, mIntermediateMat.rows(), 0, mIntermediateMat.cols());

        mIntermediateMat.copyTo(ROI);
    }

注意:

• 这些示例可能是特定于方向的，我制作它们是为了横向。
• 您不应为每个视频帧调用这些示例中的代码。有些代码应该只运行一次。