AlphaTransformation for Glide 3.7.0

AlphaTransformation.java

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.Transformation;
import com.bumptech.glide.load.engine.Resource;
import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
import com.bumptech.glide.load.resource.bitmap.BitmapResource;

public class AlphaTransformation implements Transformation<Bitmap> {

    private BitmapPool mBitmapPool;
    private int alpha;

    public AlphaTransformation(Context context, int alpha) {
        this(Glide.get(context).getBitmapPool());
        this.alpha = alpha;
    }

    public AlphaTransformation(BitmapPool pool) {
        mBitmapPool = pool;
    }

    @Override
    public Resource<Bitmap> transform(Resource<Bitmap> resource, int outWidth, int outHeight) {
        Bitmap source = resource.get();

        int width = source.getWidth();
        int height = source.getHeight();

        Bitmap.Config config =
                source.getConfig() != null ? source.getConfig() : Bitmap.Config.ARGB_8888;
        Bitmap bitmap = mBitmapPool.get(width, height, config);
        if (bitmap == null) {
            bitmap = Bitmap.createBitmap(width, height, config);
        }

        Canvas canvas = new Canvas(bitmap);
        Paint paint = new Paint();
        paint.setAlpha(alpha);
        canvas.drawBitmap(source, 0, 0, paint);

        return BitmapResource.obtain(bitmap, mBitmapPool);
    }

    /*
    getId()) method describes an unique identifier for this particular transformation.
    Glide uses that key as part of the caching system.
    Makes sure to make it unique to avoid unexpected issues.
     */
    @Override public String getId() {
        return "AlphaTransformation()";
    }
}