Java tutorial
/* * Copyright 2012-2015 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.boot; import java.awt.Color; import java.awt.Image; import java.awt.image.BufferedImage; import java.io.IOException; import java.io.InputStream; import java.io.PrintStream; import javax.imageio.ImageIO; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.springframework.boot.ansi.AnsiBackground; import org.springframework.boot.ansi.AnsiColor; import org.springframework.boot.ansi.AnsiColors; import org.springframework.boot.ansi.AnsiElement; import org.springframework.boot.ansi.AnsiOutput; import org.springframework.boot.bind.RelaxedPropertyResolver; import org.springframework.core.env.Environment; import org.springframework.core.env.PropertyResolver; import org.springframework.core.io.Resource; import org.springframework.util.Assert; /** * Banner implementation that prints ASCII art generated from an image resource * {@link Resource}. * * @author Craig Burke * @author Phillip Webb * @since 1.4.0 */ public class ImageBanner implements Banner { private static final Log log = LogFactory.getLog(ImageBanner.class); private static final double[] RGB_WEIGHT = { 0.2126d, 0.7152d, 0.0722d }; private static final char[] PIXEL = { ' ', '.', '*', ':', 'o', '&', '8', '#', '@' }; private static final int LUMINANCE_INCREMENT = 10; private static final int LUMINANCE_START = LUMINANCE_INCREMENT * PIXEL.length; private final Resource image; public ImageBanner(Resource image) { Assert.notNull(image, "Image must not be null"); Assert.isTrue(image.exists(), "Image must exist"); this.image = image; } @Override public void printBanner(Environment environment, Class<?> sourceClass, PrintStream out) { String headless = System.getProperty("java.awt.headless"); try { System.setProperty("java.awt.headless", "true"); printBanner(environment, out); } catch (Throwable ex) { log.warn("Image banner not printable: " + this.image + " (" + ex.getClass() + ": '" + ex.getMessage() + "')"); log.debug("Image banner printing failure", ex); } finally { if (headless == null) { System.clearProperty("java.awt.headless"); } else { System.setProperty("java.awt.headless", headless); } } } private void printBanner(Environment environment, PrintStream out) throws IOException { PropertyResolver properties = new RelaxedPropertyResolver(environment, "banner.image."); int width = properties.getProperty("width", Integer.class, 76); int height = properties.getProperty("height", Integer.class, 0); int margin = properties.getProperty("margin", Integer.class, 2); boolean invert = properties.getProperty("invert", Boolean.class, false); BufferedImage image = readImage(width, height); printBanner(image, margin, invert, out); } private BufferedImage readImage(int width, int height) throws IOException { InputStream inputStream = this.image.getInputStream(); try { BufferedImage image = ImageIO.read(inputStream); return resizeImage(image, width, height); } finally { inputStream.close(); } } private BufferedImage resizeImage(BufferedImage image, int width, int height) { if (width < 1) { width = 1; } if (height <= 0) { double aspectRatio = (double) width / image.getWidth() * 0.5; height = (int) Math.ceil(image.getHeight() * aspectRatio); } BufferedImage resized = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Image scaled = image.getScaledInstance(width, height, Image.SCALE_DEFAULT); resized.getGraphics().drawImage(scaled, 0, 0, null); return resized; } private void printBanner(BufferedImage image, int margin, boolean invert, PrintStream out) { AnsiElement background = (invert ? AnsiBackground.BLACK : AnsiBackground.DEFAULT); out.print(AnsiOutput.encode(AnsiColor.DEFAULT)); out.print(AnsiOutput.encode(background)); out.println(); out.println(); AnsiColor lastColor = AnsiColor.DEFAULT; for (int y = 0; y < image.getHeight(); y++) { for (int i = 0; i < margin; i++) { out.print(" "); } for (int x = 0; x < image.getWidth(); x++) { Color color = new Color(image.getRGB(x, y), false); AnsiColor ansiColor = AnsiColors.getClosest(color); if (ansiColor != lastColor) { out.print(AnsiOutput.encode(ansiColor)); lastColor = ansiColor; } out.print(getAsciiPixel(color, invert)); } out.println(); } out.print(AnsiOutput.encode(AnsiColor.DEFAULT)); out.print(AnsiOutput.encode(AnsiBackground.DEFAULT)); out.println(); } private char getAsciiPixel(Color color, boolean dark) { double luminance = getLuminance(color, dark); for (int i = 0; i < PIXEL.length; i++) { if (luminance >= (LUMINANCE_START - (i * LUMINANCE_INCREMENT))) { return PIXEL[i]; } } return PIXEL[PIXEL.length - 1]; } private int getLuminance(Color color, boolean inverse) { double luminance = 0.0; luminance += getLuminance(color.getRed(), inverse, RGB_WEIGHT[0]); luminance += getLuminance(color.getGreen(), inverse, RGB_WEIGHT[1]); luminance += getLuminance(color.getBlue(), inverse, RGB_WEIGHT[2]); return (int) Math.ceil((luminance / 0xFF) * 100); } private double getLuminance(int component, boolean inverse, double weight) { return (inverse ? 0xFF - component : component) * weight; } }