come from http://square.github.io/picasso/ . Aiming to get a square thumbs, note about the way to get the central size for both width and height

bitmap circle .java

Transformation transformation = new Transformation() {

            @Override
            public Bitmap transform(Bitmap source) {
                if(null == source){
                    return null;
                }

                int size = Math.min(source.getWidth(), source.getHeight());

                int x = (source.getWidth() - size) / 2;
                int y = (source.getHeight() - size) / 2;

                Bitmap squaredBitmap = Bitmap.createBitmap(source, x, y, size, size);
                if (squaredBitmap != source) {
                    source.recycle();
                }

                Bitmap bitmap = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888);

                Canvas canvas = new Canvas(bitmap);
                Paint paint = new Paint();
                BitmapShader shader = new BitmapShader(squaredBitmap, BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP);
                paint.setShader(shader);
                paint.setAntiAlias(true);

                float r = size / 2f;
                canvas.drawCircle(r, r, r, paint);

                squaredBitmap.recycle();
                return bitmap;
            }


            @Override
            public String key() {
                return "cycle";
            }
        };

bitmap cropSquare.java

public class CropSquareTransformation implements Transformation {
  @Override public Bitmap transform(Bitmap source) {
    int size = Math.min(source.getWidth(), source.getHeight());
    int x = (source.getWidth() - size) / 2;
    int y = (source.getHeight() - size) / 2;
    Bitmap result = Bitmap.createBitmap(source, x, y, size, size);
    if (result != source) {
      source.recycle();
    }
    return result;
  }

  @Override public String key() { return "square()"; }
}