Maintain aspect ratio of bitmap drawables set as windowBackground on Android

CenterCropDrawable.java

import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Matrix;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.support.annotation.IntRange;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;

/**
 * Drawable decorator which draws the target drawable similarly to an ImageView with scaleType=centerCrop
 *
 * Example usage:
 *     final Drawable bg = getResources().getDrawable(R.drawable.screen);
 *     getWindow().setBackgroundDrawable(new CenterCropDrawable(bg));
 */
public class CenterCropDrawable extends Drawable {

    @NonNull
    private final Drawable target;

    public CenterCropDrawable(@NonNull Drawable target) {
        this.target = target;
    }

    @Override
    public void setBounds(@NonNull Rect bounds) {
        super.setBounds(bounds.left, bounds.top, bounds.right, bounds.bottom);
    }

    @Override
    public void setBounds(int left, int top, int right, int bottom) {
        final RectF sourceRect = new RectF(0, 0, target.getIntrinsicWidth(), target.getIntrinsicHeight());
        final RectF screenRect = new RectF(left, top, right, bottom);

        final Matrix matrix = new Matrix();
        matrix.setRectToRect(screenRect, sourceRect, Matrix.ScaleToFit.CENTER);

        final Matrix inverse = new Matrix();
        matrix.invert(inverse);
        inverse.mapRect(sourceRect);

        target.setBounds(Math.round(sourceRect.left), Math.round(sourceRect.top),
                         Math.round(sourceRect.right), Math.round(sourceRect.bottom));

        super.setBounds(left, top, right, bottom);
    }

    @Override
    public void draw(@NonNull Canvas canvas) {
        canvas.save(Canvas.CLIP_SAVE_FLAG);
        canvas.clipRect(getBounds());
        target.draw(canvas);
        canvas.restore();
    }

    @Override
    public void setAlpha(@IntRange(from = 0, to = 255) int alpha) {
        target.setAlpha(alpha);
    }

    @Override
    public void setColorFilter(@Nullable ColorFilter colorFilter) {
        target.setColorFilter(colorFilter);
    }

    @Override
    public int getOpacity() {
        return target.getOpacity();
    }
}

Great work thanks! ...

you might update
Canvas.CLIP_SAVE_FLAG to Canvas.ALL_SAVE_FLAG

Hi. Can someone explain the code? This resolved my problem...but I can't get it. Thank you.

Hey @CrandellWS
Why do you think we should use theCanvas.ALL_SAVE_FLAG?
As I see it, I only change clip rectangle so this is the only thing I need to save and restore. This should be significantly cheaper than saving/restoring the entire Canvas state.

Sorry for the late reply :)

Hey @pedroRelvas

Which part of it you don't understand?
Here are some references which might help to get it:

https://en.wikipedia.org/wiki/Decorator_pattern
https://www.cs.utexas.edu/users/fussell/courses/cs384g-fall2011/lectures/lecture07-Affine.pdf
https://developer.android.com/reference/android/graphics/Matrix
https://developer.android.com/reference/android/graphics/drawable/Drawable

Hi) Great solution, but on some devices does enamation freeze? What could be the problem ?

Here in this version, it freeze on some devices:
animationBackground = (AnimatedVectorDrawable) getDrawable(R.drawable.splash_screen_anim); getWindow().setBackgroundDrawable(new CenterCropDrawable(animationBackground));

But, if you changed the code and remove new CenterCropDrawable, then the animation stops freezing on these devices:
animationBackground = (AnimatedVectorDrawable) getDrawable(R.drawable.splash_screen_anim); getWindow().setBackgroundDrawable(animationBackground);

Hi @pchell

What is your animation? Could it be that CenterCropDrawable overrides every frame of your animanation by, well, centering the drawable?

Hi @rudchenkos !
I use animated-vector. I created a question on https://stackoverflow.com/questions/62166507/setanimatedvectordrawable-start-does-not-work-on-some-devices. I would be very grateful if you could help resolve the issue)