Here you can find the source of getScaleToFit(JPanel componentToFit, File imageFile)
public static double getScaleToFit(JPanel componentToFit, File imageFile) throws IOException
//package com.java2s; /**//from www .j a va 2 s. c o m * @(#)ImageHelper.java * * This file is part of the Non-Linear Book project. * Copyright (c) 2012-2015 Anton P. Kolosov * Authors: Anton P. Kolosov, et al. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License version 3 * as published by the Free Software Foundation with the addition of the * following permission added to Section 15 as permitted in Section 7(a): * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY * ANTON P. KOLOSOV. ANTON P. KOLOSOV DISCLAIMS THE WARRANTY OF NON INFRINGEMENT * OF THIRD PARTY RIGHTS * * This program 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 Affero General Public License for more details. * You should have received a copy of the GNU Affero General Public License * along with this program; if not, see http://www.gnu.org/licenses or write to * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, * Boston, MA, 02110-1301 USA. * * The interactive user interfaces in modified source and object code versions * of this program must display Appropriate Legal Notices, as required under * Section 5 of the GNU Affero General Public License. * * You can be released from the requirements of the license by purchasing * a commercial license. Buying such a license is mandatory as soon as you * develop commercial activities involving the Non-Linear Book software without * disclosing the source code of your own applications. * * For more information, please contact Anton P. Kolosov at this * address: antokolos@gmail.com * * Copyright (c) 2015 Anton P. Kolosov All rights reserved. */ import java.awt.image.BufferedImage; import java.io.File; import java.io.IOException; import javax.imageio.ImageIO; import javax.swing.*; public class Main { public static double getScaleToFit(JPanel componentToFit, File imageFile) throws IOException { BufferedImage bimg = ImageIO.read(imageFile); int width = bimg.getWidth(); int height = bimg.getHeight(); double scalex = componentToFit.getVisibleRect().getWidth() / (double) width; double scaley = componentToFit.getVisibleRect().getHeight() / (double) height; return (scalex < scaley) ? scalex : scaley; } }