Android: How to rotate a bitmap on a center point

Question

I've been looking for over a day for a solution to this problem but nothing helps, even the answers here. Documentation doesn't explain anything too.

I am simply trying to get a rotation in the direction of another object. The problem is that the bitmap is not rotated around a fixed point, but rather around the bitmaps (0,0).

Here is the code I am having troubles with:

  Matrix mtx = new Matrix();   mtx.reset();   mtx.preTranslate(-centerX, -centerY);   mtx.setRotate((float)direction, -centerX, -centerY);   mtx.postTranslate(pivotX, pivotY);   Bitmap rotatedBMP = Bitmap.createBitmap(bitmap, 0, 0, spriteWidth, spriteHeight, mtx, true);   this.bitmap = rotatedBMP; 

The weird part is, it doesn't matter how I change the values within pre/postTranslate() and the float arguments in setRotation(). Can someone please help and push me in the right direction? :)

Answer 1

I hope the following sequence of code will help you:

Bitmap targetBitmap = Bitmap.createBitmap(targetWidth, targetHeight, config); Canvas canvas = new Canvas(targetBitmap); Matrix matrix = new Matrix(); matrix.setRotate(mRotation,source.getWidth()/2,source.getHeight()/2); canvas.drawBitmap(source, matrix, new Paint()); 

If you check the following method from ~frameworks\base\graphics\java\android\graphics\Bitmap.java

public static Bitmap createBitmap(Bitmap source, int x, int y, int width, int height,         Matrix m, boolean filter) 

this would explain what it does with rotation and translate.