Rotate An Image Multiple Times But Keep The Corners Aligned

I tried to rotate an image with following code, but I found the generated image gets bigger and bigger: Matrix matrix = new Matrix(); matrix.setRotate(10); Bitmap newImage = Bitmap

Solution 1:

I tried your code and after some rotation it crashed with the OutOfMemory exception cause each time a new bitmap is created which is very resource intensive. You should never never! use createBitMap() in iteration. I made some modification to your image rotation code and now it's running as expected.
Here is the code:

private void addListeners() {
    this.button.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View view) {

            Matrix matrix = new Matrix();

            //copying the image matrix(source) to this matrix 
            matrix.set(imageView.getImageMatrix());

            matrix.postRotate(10, imageView.getWidth()/2, imageView.getHeight()/2);
            imageView.setImageMatrix(matrix);

            //checking the size of the image
            Drawable d = imageView.getDrawable();
            Bitmap bmp = ((BitmapDrawable)d).getBitmap();
            imageInfo(bmp);
        }
    });
}

also set the scale type of the imageView to matrix

<ImageView
    android:id="@+id/Image"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="#336699"
    android:scaleType="matrix"
    android:padding="2px"
    android:src="@drawable/m" />

And if we want to get the rotated bitmap from ImageView, do this:

private Bitmap getBitmapFromView() {
    // this is the important code :)
    // Without it the view will have a dimension of 0,0 and the bitmap will be null
    imageView.setDrawingCacheEnabled(true);
    imageView.measure(View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED),
            View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
    imageView.layout(0, 0, imageView.getMeasuredWidth(), imageView.getMeasuredHeight());
    imageView.buildDrawingCache(true);
    Bitmap b = Bitmap.createBitmap(imageView.getDrawingCache());
    imageView.setDrawingCacheEnabled(false); // clear drawing cache
    return b;
}

I hope this helps.

Solution 2:

I can't seem to see your images, yet I had the same problem, each time I tried to rotate an image it seemed to resize its self.

I managed to write some code that could successfully turn my image. My first tip to you is that when you attempt to create an animated spinning picture you should not create a new Bitmap every time, since this will drive the GC crazy and reduce performance speed!

Here's the code that works for me, to spin an image without resizing it:

public static Matrix rotateMatrix(Bitmap bitmap, Shape shape, int rotation) {

        float scaleWidth = ((float) shape.getWidth()) / bitmap.getWidth();
        float scaleHeight = ((float) shape.getHeight()) / bitmap.getHeight();

        Matrix rotateMatrix = new Matrix();
        rotateMatrix.postScale(scaleWidth, scaleHeight);
        rotateMatrix.postRotate(rotation, shape.getWidth()/2, shape.getHeight()/2);
        rotateMatrix.postTranslate(shape.getX(), shape.getY());


        return rotateMatrix;

    }

Note: The shape object just contains the real dimensions of the object you are trying to spin, eg 100x100.

I hope this helps.

Solution 3:

You must rotate the first image. Save the first image into a variable and then create a copy. When you rotate, always make a fresh copy from the original and rotate that one.

EDIT

Change your code to this:

 @Override
        public void onClick(View view) {
            Matrix matrix = new Matrix();
            matrix.setRotate(10);
            Bitmap copy = image;
            Bitmap newImage = Bitmap.createBitmap(copy, 0, 0, image.getWidth(), image.getHeight(), matrix, true);
            setNewImage(newImage);
        }