How to auto crop an image white border in Java?

Question

What\'s the easiest way to auto crop the white border out of an image in java? Thanks in advance...

Answer 1

Here's a way to crop all 4 sides, using the color from the very top-left pixel as the baseline, and allow for a tolerance of color variation so that noise in the image won't make the crop useless

public BufferedImage getCroppedImage(BufferedImage source, double tolerance) {
   // Get our top-left pixel color as our "baseline" for cropping
   int baseColor = source.getRGB(0, 0);

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

   int topY = Integer.MAX_VALUE, topX = Integer.MAX_VALUE;
   int bottomY = -1, bottomX = -1;
   for(int y=0; y bottomX) bottomX = x;
            if (y > bottomY) bottomY = y;
         }
      }
   }

   BufferedImage destination = new BufferedImage( (bottomX-topX+1), 
                 (bottomY-topY+1), BufferedImage.TYPE_INT_ARGB);

   destination.getGraphics().drawImage(source, 0, 0, 
               destination.getWidth(), destination.getHeight(), 
               topX, topY, bottomX, bottomY, null);

   return destination;
}

private boolean colorWithinTolerance(int a, int b, double tolerance) {
    int aAlpha  = (int)((a & 0xFF000000) >>> 24);   // Alpha level
    int aRed    = (int)((a & 0x00FF0000) >>> 16);   // Red level
    int aGreen  = (int)((a & 0x0000FF00) >>> 8);    // Green level
    int aBlue   = (int)(a & 0x000000FF);            // Blue level

    int bAlpha  = (int)((b & 0xFF000000) >>> 24);   // Alpha level
    int bRed    = (int)((b & 0x00FF0000) >>> 16);   // Red level
    int bGreen  = (int)((b & 0x0000FF00) >>> 8);    // Green level
    int bBlue   = (int)(b & 0x000000FF);            // Blue level

    double distance = Math.sqrt((aAlpha-bAlpha)*(aAlpha-bAlpha) +
                                (aRed-bRed)*(aRed-bRed) +
                                (aGreen-bGreen)*(aGreen-bGreen) +
                                (aBlue-bBlue)*(aBlue-bBlue));

    // 510.0 is the maximum distance between two colors 
    // (0,0,0,0 -> 255,255,255,255)
    double percentAway = distance / 510.0d;     

    return (percentAway > tolerance);
}