Java tutorial
/* * Copyright (c) 2014 tabletoptool.com team. * All rights reserved. This program and the accompanying materials * are made available under the terms of the GNU Public License v3.0 * which accompanies this distribution, and is available at * http://www.gnu.org/licenses/gpl.html * * Contributors: * rptools.com team - initial implementation * tabletoptool.com team - further development */ package com.t3.image; import java.awt.Dimension; import java.awt.Graphics2D; import java.awt.Image; import java.awt.RenderingHints; import java.awt.image.BufferedImage; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; import javax.imageio.ImageIO; import org.apache.commons.io.IOUtils; import com.t3.MD5Key; import com.t3.swing.SwingUtil; public class ThumbnailManager { private File thumbnailLocation; private Dimension thumbnailSize; public ThumbnailManager(File thumbnailLocation, Dimension thumbnailSize) { this.thumbnailLocation = thumbnailLocation; this.thumbnailSize = thumbnailSize; } public Image getThumbnail(File file) throws IOException { // Cache BufferedImage thumbnail = getCachedThumbnail(file); if (thumbnail != null) { return thumbnail; } // Create return createThumbnail(file); } private Image createThumbnail(File file) throws IOException { // Gather info File thumbnailFile = getThumbnailFile(file); if (thumbnailFile.exists()) { return ImageUtil.getImage(thumbnailFile); } Image image = ImageUtil.getImage(file); // Should we bother making a thumbnail ? if (file.length() < 30 * 1024) { return image; } // Transform the image Dimension imgSize = new Dimension(image.getWidth(null), image.getHeight(null)); SwingUtil.constrainTo(imgSize, thumbnailSize.width, thumbnailSize.height); BufferedImage thumbnailImage = new BufferedImage(imgSize.width, imgSize.height, ImageUtil.pickBestTransparency(image)); Graphics2D g = thumbnailImage.createGraphics(); g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY); g.drawImage(image, 0, 0, imgSize.width, imgSize.height, null); g.dispose(); // Ensure path exists if (thumbnailFile.exists()) thumbnailFile.delete(); else thumbnailFile.getParentFile().mkdirs(); try (OutputStream os = new FileOutputStream(thumbnailFile)) { IOUtils.write(ImageUtil.imageToBytes(thumbnailImage, "png"), os); } return thumbnailImage; } private BufferedImage getCachedThumbnail(File file) { File thumbnailFile = getThumbnailFile(file); if (!thumbnailFile.exists()) { return null; } try { // Check that it hasn't changed on disk if (file.lastModified() > thumbnailFile.lastModified()) { return null; } // Get the thumbnail BufferedImage thumbnail = ImageIO.read(thumbnailFile); // Check that we have the size we want if (thumbnail.getWidth() != thumbnailSize.width && thumbnail.getHeight() != thumbnailSize.height) { return null; } return thumbnail; } catch (IOException ioe) { return null; } } private File getThumbnailFile(File file) { MD5Key key = new MD5Key(file.getAbsolutePath().getBytes()); return new File(thumbnailLocation.getPath() + "/" + key); } }