How to rotate image using opencv

Question

I'm trying to rotate image. Code below can rotate an image successfully but it cuts off corners of the image and it rotates in wrong direction. What could be the problem? I would be grateful if someone give me some advice. Here is the code :

public void findAngle(){
    FloatBuffer deskew_angle = FloatBuffer.allocate(1);
    IntBuffer orientation = IntBuffer.allocate(1);
    IntBuffer writing_direction = IntBuffer.allocate(1);
    IntBuffer textline_order = IntBuffer.allocate(1);
    final TessAPI api = TessAPI.INSTANCE;

    final TessBaseAPI handle;
    handle = api.TessBaseAPICreate();
    api.TessBaseAPIInit3(handle, "C:\\Program Files\\Tesseract-OCR\\tessdata", "eng");
    api.TessBaseAPISetVariable(handle, "tessedit_char_whitelist",
            "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ?!.,:-");
    File tiff = new File("C:\\Users\\A\\Desktop\\1.jpg");
    BufferedImage image = null;
    try {
        image = ImageIO.read(new FileInputStream(tiff));
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } // require jai-imageio lib to read TIFF
    ByteBuffer buf = ImageIOHelper.convertImageData(image);
    int bpp = image.getColorModel().getPixelSize();
    int bytespp = bpp / 8;
    int bytespl = (int) Math.ceil(image.getWidth() * bpp / 8.0);
    api.TessBaseAPISetPageSegMode(handle, TessAPI.TessPageSegMode.PSM_AUTO_OSD);
    api.TessBaseAPISetImage(handle, buf, image.getWidth(), image.getHeight(), bytespp, bytespl);
    TessPageIterator pi = api.TessBaseAPIAnalyseLayout(handle);
    api.TessPageIteratorOrientation(pi, orientation, writing_direction, textline_order, deskew_angle);

    float angle = deskew_angle.get(0);
    System.out.println("Angle : "+angle);

    System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
    String resultString = "";

    Mat frame = Imgcodecs.imread(lFile, Imgcodecs.CV_LOAD_IMAGE_GRAYSCALE);
    Point center = new Point(350,350);
    if(angle == 270 || angle == -90) {
        Mat rotImage = Imgproc.getRotationMatrix2D(center, angle, 1);
        Imgproc.warpAffine(frame, frame, rotImage, new Size(frame.cols(),frame.cols()));
    }
    else if (angle == 180 || angle == -180 ){
        Mat rotImage = Imgproc.getRotationMatrix2D(center, angle, 1);
        Imgproc.warpAffine(frame, frame, rotImage, new Size(frame.cols(),frame.cols()));
    }
    else if(angle == 90 || angle == -270) {
        Mat rotImage = Imgproc.getRotationMatrix2D(center, angle, 1);
        Imgproc.warpAffine(frame, frame, rotImage, new Size(frame.cols(),frame.cols()));
    }
    else if(angle == 360 || angle == 0 || angle == -360) {
        Mat rotImage = Imgproc.getRotationMatrix2D(center, angle, 0.65);
        Imgproc.warpAffine(frame, frame, rotImage, new Size(frame.cols(),frame.cols()));
    }

    System.out.println(String.format(
            "Orientation: %s\nWritingDirection: %s\nTextlineOrder: %s\nDeskew angle: %.4f\n",
            Utils.getConstantName(orientation.get(), TessOrientation.class),
            Utils.getConstantName(writing_direction.get(), TessWritingDirection.class),
            Utils.getConstantName(textline_order.get(), TessTextlineOrder.class),
            deskew_angle.get(0)));
    api.TessBaseAPIClear(handle);
    api.TessBaseAPIEnd(handle);
    api.TessBaseAPIDelete(handle);
    Imgcodecs.imwrite("C:\\Users\\A\\Desktop\\a.jpg", img);
    }

And rotated image's background is black but I want it to be transparent or white. Following is the code https://stackoverflow.com/a/45559068/9994984 I'm trying to all steps but not working correctly. Thanks in advance.

Alternative to rotate image check below link, https://stackoverflow.com/questions/46657423/rotated-image-coordinates-after-scipy-ndimage-interpolation-rotate — Ethan Hunt 007, Mar 12 '19 at 13:59

score -1 · Answer 1 · answered Mar 12 '19 at 15:04

-1

Cuz you don't change the image's size when you rotate it; 1.if you don't want to change the image's size,you shoud increase the window's size,because when you rotate image,the window's width and height is not enough; 2.if you dont want to change the window's size,so you should reduce the image's size.

answered Mar 12 '19 at 15:04

liwei ni

1
1

Can you give an example? – parafdaatarim Mar 13 '19 at 15:13

How to rotate image using opencv

1 Answers1