Animate image's saturation

Question

Is it possible to animate the saturation of an image (eg png) over time? For example from grayscale to full color. Plus if I can use an Interpolator.

I have seen the EffectFactory and the ColorMatrix classes but I cannot combine them with an animation/transition.

Eg applying grayscale saturation on a Drawable drawable :

ColorMatrix matrix = new ColorMatrix();
matrix.setSaturation(0);

ColorMatrixColorFilter filter = new ColorMatrixColorFilter(matrix);
drawable.setColorFilter(filter);

and for full saturation later:

matrix.setSaturation(1);

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For anyone interested my full solution based on Simon's answer:

final ColorMatrix matrix = new ColorMatrix();
final Drawable drawable = ... ;

ValueAnimator animation = ValueAnimator.ofFloat(0f, 1f);
animation.setDuration(1000);
//   animation.setInterpolator();
animation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
        matrix.setSaturation(animation.getAnimatedFraction());
        ColorMatrixColorFilter filter = new ColorMatrixColorFilter(matrix);
        drawable.setColorFilter(filter);
    }
});
animation.start();

Answer 1

It certainly could be achieved with a ValueAnimator:

ValueAnimator animation = ValueAnimator.ofFloat(0f, 1f);
animation.setDuration(1000);
animation.addUpdateListener(new AnimatorUpdateListener() {
    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
        matrix.setSaturation(animation.getAnimatedFraction());
    }
});
animation.start();

Answer 2

You have to animate it yourself!

Should not be that hard.

See the ColorMatrix example in the API's demos folder.

http://alvinalexander.com/java/jwarehouse/android-examples/platforms/android-2/samples/ApiDemos/src/com/example/android/apis/graphics/ColorMatrixSample.java.shtml

You can extend Drawable and increment a value in the onDraw method and then set the filter accordingly.

You get the animation by calling invalidate() every few ms in onDraw . Be sure to slow down the iterations by puting the thread to sleep. Thread.sleep(40); for 25 fps