How to mirror an image file? (2.2+)

android image image-manipulation
Force picture Force · Dec 18, 2011 · Viewed 8.8k times · Source

I have a PNG file that I want to use for an overlay - however, this file has to be mirrored (and rotated by 180°), but in order to save space, I don't want to place the mirrored file in the apk, but do this action programmatically.

How can I do this with Froyo and above?

Answer

Dalmas picture Dalmas · Dec 18, 2011

Scaling by -1.0 causes the image to be flipped. Assuming bmp is the bitmap you want to mirror (here on the x axis) you can do :

Matrix matrix = new Matrix(); 
matrix.preScale(-1.0f, 1.0f); 
Bitmap mirroredBitmap = Bitmap.createBitmap(bmp, 0, 0, bmp.width(), bmp.height(), matrix, false);

If you don't want to create a second bitmap, you can do the same with canvas.scale :

canvas.save();
canvas.scale(-1.0f, 1.0f);
canvas.drawBitmap(bitmap, ...); // The bitmap is flipped
canvas.restore();

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