How to make bitmap transparent?

Question

/**
 * @param bitmap
 *            The source bitmap.
 * @param opacity
 *            a value between 0 (completely transparent) and 255 (completely
 *            op         


        

Answer 1

Try this. Also note that setAlpha is in 0-255 range

//bmp is your Bitmap object

BitmapDrawable bd = new BitmapDrawable(bmp);
bd.setAlpha(50);

ImageView v = (ImageView) findViewById(R.id.image);
v.setImageDrawable(bd);

Answer 2

Add method

Bitmap bmp; DrawView DrawView;

private static Bitmap makeTransparentBitmap(Bitmap bmp, int alpha) {
        Bitmap transBmp = Bitmap.createBitmap(bmp.getWidth(),
                bmp.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(transBmp);
        final Paint paint = new Paint();
        paint.setAlpha(alpha);
        canvas.drawBitmap(bmp, 0, 0, paint);
        return transBmp;
    }


@Override
protected void onDraw(Canvas canvas) {
    canvas.drawColor(Color.rgb(43,44,45));

    bmp = BitmapFactory.decodeResource(getResources(), R.drawable.mouse);
    canvas.drawBitmap(bmp, pos_x, pos_y, null); 

}

You event:

bmp = makeTransparentBitmap( bmp, 122 );
DrawView.invalidate();

DrawView is

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    DrawView = new DrawView(this);
    setContentView( DrawView );
}

I found this answer here

Answer 3

Making an existing bitmap transparent is too simple.

If you want to make your bitmap transparent before further drawing follow this.

if your bitmap is mBitmap then Just use:-

mBitmap.eraseColor(Color.TRANSPARENT) 

Thats it. Good luck !!

Answer 4

@akaya's answer is the right way except that the constructor is deprecated. The new way since API 4 would be to use:

BitmapDrawable drawable = new BitmapDrawable(getResources(), bitmap);
drawable.setAlpha(100);

Answer 5

// Convert transparentColor to be transparent in a Bitmap.
public static Bitmap makeTransparent(Bitmap bit, Color transparentColor) {
    int width =  bit.getWidth();
    int height = bit.getHeight();
    Bitmap myBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    int [] allpixels = new int [ myBitmap.getHeight()*myBitmap.getWidth()];
    bit.getPixels(allpixels, 0, myBitmap.getWidth(), 0, 0, myBitmap.getWidth(),myBitmap.getHeight());
    myBitmap.setPixels(allpixels, 0, width, 0, 0, width, height);

    for(int i =0; i<myBitmap.getHeight()*myBitmap.getWidth();i++){
     if( allpixels[i] == transparentColor)

                 allpixels[i] = Color.alpha(Color.TRANSPARENT);
     }

      myBitmap.setPixels(allpixels, 0, myBitmap.getWidth(), 0, 0, myBitmap.getWidth(), myBitmap.getHeight());
      return myBitmap;
}

The above code will take a Bitmap, and return a Bitmap where every pixel which the color is transparentColor is transparent. This works in API as low as level 8, and I have not tested it in any lower.

I typically use something like Color.RED to make my transparent pixels, because I don't use a lot of RED in my assets, but if I do it's a custom red color.

Answer 6

try this,

newBitmap.setImageResource(android.R.color.transparent);