Android - Setting bitmap collision detection after rotation by matrix

How do I create code for collision d开发者_JAVA百科etection on a bitmap rotated by a matrix?

canvas.drawBitmap(mAnimation, mainMatrix, null);

mainMatrix is derived from a PathMeasure so i do not know the rotation The bitmap is rotated around x=0,y=0 and thus a circle around the centre will not work (or at least be too big)

thanks

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Matrix has a method to map points and rectangles, you could use that to know the result of the transformation.