Java tutorial
/* * Copyright 2012-2019 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 * * https://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 java.util.Iterator; import javax.imageio.ImageIO; import javax.imageio.ImageReadParam; import javax.imageio.ImageReader; import javax.imageio.metadata.IIOMetadata; import javax.imageio.metadata.IIOMetadataNode; import javax.imageio.stream.ImageInputStream; 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.core.env.Environment; 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 * @author Madhura Bhave * @author Raja Kolli * @since 1.4.0 */ public class ImageBanner implements Banner { private static final String PROPERTY_PREFIX = "spring.banner.image."; private static final Log logger = 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) { logger.warn("Image banner not printable: " + this.image + " (" + ex.getClass() + ": '" + ex.getMessage() + "')"); logger.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 { int width = getProperty(environment, "width", Integer.class, 76); int height = getProperty(environment, "height", Integer.class, 0); int margin = getProperty(environment, "margin", Integer.class, 2); boolean invert = getProperty(environment, "invert", Boolean.class, false); Frame[] frames = readFrames(width, height); for (int i = 0; i < frames.length; i++) { if (i > 0) { resetCursor(frames[i - 1].getImage(), out); } printBanner(frames[i].getImage(), margin, invert, out); sleep(frames[i].getDelayTime()); } } private <T> T getProperty(Environment environment, String name, Class<T> targetType, T defaultValue) { return environment.getProperty(PROPERTY_PREFIX + name, targetType, defaultValue); } private Frame[] readFrames(int width, int height) throws IOException { try (InputStream inputStream = this.image.getInputStream()) { try (ImageInputStream imageStream = ImageIO.createImageInputStream(inputStream)) { return readFrames(width, height, imageStream); } } } private Frame[] readFrames(int width, int height, ImageInputStream stream) throws IOException { Iterator<ImageReader> readers = ImageIO.getImageReaders(stream); Assert.state(readers.hasNext(), "Unable to read image banner source"); ImageReader reader = readers.next(); try { ImageReadParam readParam = reader.getDefaultReadParam(); reader.setInput(stream); int frameCount = reader.getNumImages(true); Frame[] frames = new Frame[frameCount]; for (int i = 0; i < frameCount; i++) { frames[i] = readFrame(width, height, reader, i, readParam); } return frames; } finally { reader.dispose(); } } private Frame readFrame(int width, int height, ImageReader reader, int imageIndex, ImageReadParam readParam) throws IOException { BufferedImage image = reader.read(imageIndex, readParam); BufferedImage resized = resizeImage(image, width, height); int delayTime = getDelayTime(reader, imageIndex); return new Frame(resized, delayTime); } private int getDelayTime(ImageReader reader, int imageIndex) throws IOException { IIOMetadata metadata = reader.getImageMetadata(imageIndex); IIOMetadataNode root = (IIOMetadataNode) metadata.getAsTree(metadata.getNativeMetadataFormatName()); IIOMetadataNode extension = findNode(root, "GraphicControlExtension"); String attribute = (extension != null) ? extension.getAttribute("delayTime") : null; return (attribute != null) ? Integer.parseInt(attribute) * 10 : 0; } private static IIOMetadataNode findNode(IIOMetadataNode rootNode, String nodeName) { if (rootNode == null) { return null; } for (int i = 0; i < rootNode.getLength(); i++) { if (rootNode.item(i).getNodeName().equalsIgnoreCase(nodeName)) { return ((IIOMetadataNode) rootNode.item(i)); } } return null; } 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 resetCursor(BufferedImage image, PrintStream out) { int lines = image.getHeight() + 3; out.print("\033[" + lines + "A\r"); } 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; } private void sleep(int delay) { try { Thread.sleep(delay); } catch (InterruptedException ex) { Thread.currentThread().interrupt(); } } private static class Frame { private final BufferedImage image; private final int delayTime; Frame(BufferedImage image, int delayTime) { this.image = image; this.delayTime = delayTime; } BufferedImage getImage() { return this.image; } int getDelayTime() { return this.delayTime; } } }