Here you can find the source of generateOutline(BufferedImage source, Color color, boolean alpha)
public static BufferedImage generateOutline(BufferedImage source, Color color, boolean alpha)
//package com.java2s; /*/*from w w w . j a v a 2 s. co m*/ * Collab canvas - Java framework for graphics software enabling offline and shared * painting * Copyright (C) 2012 Martin Indra <aktive@seznam.cz> * * This file is part of Collab canvas. * * Collab canvas is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * Collab canvas is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with Collab canvas. If not, see <http://www.gnu.org/licenses/>. */ import java.awt.Color; import java.awt.image.BufferedImage; public class Main { public static BufferedImage generateOutline(BufferedImage source, Color color, boolean alpha) { return generateOutline(source, color, color, alpha); } public static BufferedImage generateOutline(BufferedImage source, Color color1, Color color2, boolean alpha) { int w = source.getWidth(); int h = source.getHeight(); BufferedImage result = new BufferedImage(w, h, BufferedImage.TYPE_4BYTE_ABGR); for (int x = 0; x < w; x++) { for (int y = 0; y < h; y++) { if (!testNeighbour(source, x, y, alpha)) { if (testNeighbours(source, x, y, alpha)) { boolean a = ((x + y) % 10) <= 5; result.setRGB(x, y, a ? color1.getRGB() : color2.getRGB()); } } } } return result; } protected static boolean testNeighbour(BufferedImage source, int x, int y, boolean alpha) { if (x >= 0 && y >= 0 && x < source.getWidth() && y < source.getHeight()) { int gray = source.getRGB(x, y) & 0x000000ff; int alphaI = (source.getRGB(x, y) & 0xff000000) >>> 24; return (alpha && alphaI == 0) || (!alpha && gray == 255); } return true; } protected static boolean testNeighbours(BufferedImage source, int x, int y, boolean alpha) { boolean up = testNeighbour(source, x, y - 1, alpha); boolean down = testNeighbour(source, x, y + 1, alpha); boolean left = testNeighbour(source, x - 1, y, alpha); boolean right = testNeighbour(source, x + 1, y, alpha); return up || down || left || right; } }