Java tutorial
/* Copyright 2010 Emory University This file is part of Trans-Atlantic Slave Voyages. Trans-Atlantic Slave Voyages 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. Trans-Atlantic Slave Voyages 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 Trans-Atlantic Slave Voyages. If not, see <http://www.gnu.org/licenses/>. */ package edu.emory.library.tast.images; import java.awt.Graphics2D; import java.awt.RenderingHints; import java.awt.image.BufferedImage; import java.awt.image.BufferedImageOp; import java.awt.image.ConvolveOp; import java.awt.image.Kernel; import java.io.File; import java.io.IOException; import javax.faces.context.FacesContext; import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.io.FilenameUtils; import edu.emory.library.tast.AppConfig; import edu.emory.library.tast.util.StringUtils; /** * Servlet which provides data for thumbnail images. * */ public class ThumbnailServlet extends HttpServlet { private static final long serialVersionUID = 50767109010059686L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // location of images String baseUrl = AppConfig.getConfiguration().getString(AppConfig.IMAGES_URL); baseUrl = StringUtils.trimEnd(baseUrl, '/'); // image name and size String imageFileName = request.getParameter("i"); int thumbnailWidth = Integer.parseInt(request.getParameter("w")); int thumbnailHeight = Integer.parseInt(request.getParameter("h")); // image dir String imagesDir = AppConfig.getConfiguration().getString(AppConfig.IMAGES_DIRECTORY); // create the thumbnail name String thumbnailFileName = FilenameUtils.getBaseName(imageFileName) + "-" + thumbnailWidth + "x" + thumbnailHeight + ".png"; // does it exist? File thumbnailFile = new File(imagesDir, thumbnailFileName); if (thumbnailFile.exists()) { response.sendRedirect(baseUrl + "/" + thumbnailFileName); return; } // read the image File imageFile = new File(imagesDir, imageFileName); BufferedImage image = ImageIO.read(imageFile); int imageWidth = image.getWidth(); int imageHeight = image.getHeight(); BufferedImage imageCopy = new BufferedImage(imageWidth, imageHeight, BufferedImage.TYPE_INT_RGB); imageCopy.getGraphics().drawImage(image, 0, 0, imageWidth, imageHeight, 0, 0, imageWidth, imageHeight, null); // height is calculated automatically if (thumbnailHeight == 0) thumbnailHeight = (int) ((double) thumbnailWidth / (double) imageWidth * (double) imageHeight); // width is calculated automatically if (thumbnailWidth == 0) thumbnailWidth = (int) ((double) thumbnailHeight / (double) imageHeight * (double) imageWidth); // create an empty thumbnail BufferedImage thumbnail = new BufferedImage(thumbnailWidth, thumbnailHeight, BufferedImage.TYPE_INT_RGB); Graphics2D gr = thumbnail.createGraphics(); gr.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC); gr.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY); // determine the piece of the image which we want to clip int clipX1, clipX2, clipY1, clipY2; if (imageWidth * thumbnailHeight > thumbnailWidth * imageHeight) { int clipWidth = (int) Math .round(((double) thumbnailWidth / (double) thumbnailHeight) * (double) imageHeight); int imgCenterX = imageWidth / 2; clipX1 = imgCenterX - clipWidth / 2; clipX2 = imgCenterX + clipWidth / 2; clipY1 = 0; clipY2 = imageHeight; } else { int clipHeight = (int) Math .round(((double) thumbnailHeight / (double) thumbnailWidth) * (double) imageWidth); int imgCenterY = imageHeight / 2; clipX1 = 0; clipX2 = imageWidth; clipY1 = imgCenterY - clipHeight / 2; clipY2 = imgCenterY + clipHeight / 2; } // we filter the image first to get better results when shrinking if (2 * thumbnailWidth < clipX2 - clipX1 || 2 * thumbnailHeight < clipY2 - clipY1) { int kernelDimX = (clipX2 - clipX1) / (thumbnailWidth); int kernelDimY = (clipY2 - clipY1) / (thumbnailHeight); if (kernelDimX % 2 == 0) kernelDimX++; if (kernelDimY % 2 == 0) kernelDimY++; if (kernelDimX < kernelDimY) kernelDimX = kernelDimY; if (kernelDimY < kernelDimX) kernelDimY = kernelDimX; float[] blurKernel = new float[kernelDimX * kernelDimY]; for (int i = 0; i < kernelDimX; i++) for (int j = 0; j < kernelDimY; j++) blurKernel[i * kernelDimX + j] = 1.0f / (float) (kernelDimX * kernelDimY); BufferedImageOp op = new ConvolveOp(new Kernel(kernelDimX, kernelDimY, blurKernel)); imageCopy = op.filter(imageCopy, null); } // draw the thumbnail gr.drawImage(imageCopy, 0, 0, thumbnailWidth, thumbnailHeight, clipX1, clipY1, clipX2, clipY2, null); // and we are done gr.dispose(); ImageIO.write(thumbnail, "png", thumbnailFile); // redirect to it response.sendRedirect(baseUrl + "/" + thumbnailFileName); } public static String createThumbnailUrl(String imageName, int width, int height) { return createThumbnailUrl(FacesContext.getCurrentInstance().getExternalContext().getRequestContextPath(), imageName, width, height); } public static String createThumbnailUrl(FacesContext context, String imageName, int width, int height) { return createThumbnailUrl(context.getExternalContext().getRequestContextPath(), imageName, width, height); } public static String createThumbnailUrl(String contextPath, String imageName, int width, int height) { StringBuffer buff = new StringBuffer(); appendThumbnailUrl(buff, contextPath, imageName, width, height); return buff.toString(); } public static StringBuffer appendThumbnailUrl(StringBuffer buff, String contextPath, String imageName, int width, int height) { buff.append(contextPath); buff.append("/servlet/thumbnail"); buff.append("?i=").append(imageName); buff.append("&w=").append(width); buff.append("&h=").append(height); return buff; } }