Set rotation and position of bitmap

问题

I would like to know how i both can change the position of a bitmap and at the same time rotate it. Im drawing at a canvas.

Im currently using this line of code:

canvas.drawBitmap(bitmap, posX, posY, paint);

and I think using a matrix for rotation is the best option? The problem is that the line of code, posted above, doesn't take a matrix but a position.

There is also a similar line of code:

canvas.drawBitmap(bitmap, matrix, paint);

This one takes a matrix but not a position.

How should I do this?

回答1:

Matrix matrix = new Matrix();
matrix.SetRotate(90,pivotX,pivotY);
matrix.PostTranslate(positionX,positionY);
canvas.drawBitmap(bitmap, matrix , null);

In words - set the position after rotating.

回答2:

Take the position into a matrix as posMatrix and multiply it with rotation matrix. Then pass the resultant matrix as the parameter.

Edit ---

Matrix myTransformedMatrix = new Matrix();
myTransformedMatrix.setRotate(<rotation in dergrees>);
myTransformedMatrix.setTranslate(<translation in points>);

canvas.drawBitmap(bitmap, myTransformedMatrix, paint);

for more info on matrix class go to http://developer.android.com/reference/android/graphics/Matrix.html

来源：https://stackoverflow.com/questions/13110796/set-rotation-and-position-of-bitmap