Draw on BufferedImage with transparent background Java

 Draw on BufferedImage with transparent background Java

 If your Buffered Image has transparent background & you want to use transparent color to draw to solve erase purpose then follow the code given below.

  void eraseCanvase(int x1, int y1, int x2, int y2) {
          int  eraserWidth=10;
         Graphics g = OSC.getGraphics();
         int dist = Math.max(Math.abs(x2-x1),Math.abs(y2-y1));
          double dx = (double)(x2-x1)/dist;
         double dy = (double)(y2-y1)/dist;
         for (int d = 1; d <= dist; d++) {
            int x = (int)Math.round(x1 + dx*d);
            int y = (int)Math.round(y1 + dy*d);
                   // Erase a 10-by-10 block by default  of pixels around (x,y) Customizable.
               if( g instanceof Graphics2D ){
                    Graphics2D g2d = (Graphics2D) g;
                    // make sure the background is filled with transparent pixels when cleared !
                    g2d.setBackground(new Color(0,0,0,0));
                    g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_IN, 0.0f));
                    g.clearRect(x-3, y-3, eraserWidth, eraserWidth);            
                }
               repaint(x-3,y-3,eraserWidth,eraserWidth);
            }

In code you can change the eraserWidth value as per desired ie. to make size of eraser.You should use it in case of mouse dragged event .

But if u want to use Eraser on white color BufferedImage the just follow the code

void eraseCanvase(int x1, int y1, int x2, int y2) {
          int  eraserWidth=10;
         Graphics g = OSC.getGraphics();
         g.setColor(Color.WHITE);
         int dist = Math.max(Math.abs(x2-x1),Math.abs(y2-y1));
          double dx = (double)(x2-x1)/dist;
         double dy = (double)(y2-y1)/dist;
         for (int d = 1; d <= dist; d++) {
            int x = (int)Math.round(x1 + dx*d);
            int y = (int)Math.round(y1 + dy*d);

                   // Erase a 10-by-10 block by default  of pixels around (x,y) Customizable.
                                       // Erase a 10-by-10 block of pixels around (x,y)
               g.fillRect(x-eraserWidth/2,y-eraserWidth/2,eraserWidth,eraserWidth);
               repaint(x-eraserWidth/2,y-eraserWidth/2,eraserWidth,eraserWidth);
            }