Vignette Effect help

[leving]

Hi Android Developers,

I'm newbie in Android development. This time i have a big big big stuck issue can't resolve that is "How to develop Vignette Color Effect in Android". I tried to search many many keyword and read many many thread but i still don't know how to.

Please any Android Developer in here help me or give me a clearly tutorial for that. Please help!!!

My stupid code:

float _radius = (float)(1200);
RadialGradient _gradient = new RadialGradient(_bitmap.getWidth()/2, _bitmap.getHeight()/2, _radius, Color.TRANSPARENT, Color.BLACK, Shader.TileMode.REPEAT);

Canvas _canvas = new Canvas(_bitmap);
_canvas.drawARGB(1, 252, 255, 236);

Paint _paint = new Paint();
_paint.setColor(Color.YELLOW);
_paint.setShader(_gradient);


Rect _rect = new Rect(0, 0, _bitmap.getWidth(), _bitmap.getHeight());
RectF _rectF = new RectF(_rect);

_canvas.drawColor(Color.rgb(255, 240, 247), PorterDuff.Mode.MULTIPLY);
_canvas.drawColor(Color.rgb(209, 226, 234), PorterDuff.Mode.DARKEN); //light blue
_canvas.drawColor(Color.rgb(252, 255, 236), PorterDuff.Mode.MULTIPLY);
_canvas.drawRect(_rectF, _paint);

_paint.setXfermode(new PorterDuffXfermode(Mode.LIGHTEN));
_canvas.drawBitmap(_bitmap, _rect, _rect, _paint);