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

Refer to the following code, seems to work. In your code you are defining Matrix as m but referring to it as matrix

public class FourthActivity extends Activity {
private static final int WIDTH = 50;
private static final int HEIGHT = 50;
private static final int STRIDE = 64;  

private static int[] createColors() {
    int[] colors = new int[STRIDE * HEIGHT];
    for (int y = 0; y < HEIGHT; y++) {
        for (int x = 0; x < WIDTH; x++) {
            int r = x * 255 / (WIDTH - 1);
            int g = y * 255 / (HEIGHT - 1);
            int b = 255 - Math.min(r, g);
            int a = Math.max(r, g);
            colors[y * STRIDE + x] = (a << 24) | (r << 16) | (g << 8) | b;
        }
    }
    return colors;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main2);
    final ImageView view1 = (ImageView) findViewById(R.id.imageView1);

    int[] colors = createColors();
    final Bitmap bmp1 = Bitmap.createBitmap(colors, 0, STRIDE, WIDTH, HEIGHT,
    Bitmap.Config.ARGB_8888);
    view1.setImageBitmap(bmp1);
    Button button = (Button) findViewById(R.id.button1);
    button.setOnClickListener(new OnClickListener(){
        @Override
        public void onClick(View v) {   
            Matrix matrix = new Matrix();
            matrix.setScale(2, 2);
            matrix.preRotate(45, (float) WIDTH / 2, (float) HEIGHT / 2);

            Bitmap bmp2 = Bitmap.createBitmap(bmp1, 0, 0, 
      bmp1.getWidth(), bmp1.getHeight(), matrix, true);
            ImageView view2 = (ImageView) findViewById(R.id.imageView2);
            view2.setImageBitmap(bmp2);
        }
    });
}
}