Scale & rotate Bitmap using Matrix in Android

Question

I\'m trying to scale and rotate in single operation before creting the final bitmap but the preRotate, postConcat doesn\'t seem to work.

Bitmap bmp = ... ori         


        

Answer 1

All of the previous answer assume that this change to the bitmap is being made in a view. However in my case I was making the change to be saved out. Figured I would answer it for those in a similar boat.

There are two ways to do translation. Below dx is the translation in the X axis, and dy is the translation in the Y axis. The other variables should be self explanatory.

1 - Translation within the image (without rotation)

val newBitmap = Bitmap.createBitmap(originalBitmap, dx, dy, newWidth, newHeight, matrix, false)

2 - Complex matrix

 matrix.postTranslate(dx, dy)

 val newBitmap = Bitmap.createBitmap(newWidth, newHeight, Bitmap.Config.ARGB_8888)

 val canvas = Canvas(newBitmap)
 canvas.drawBitmap(originalBitmap, matrix, null)