org.zephyrsoft.util.gui.ImagePanel.java Source code

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Here is the source code for org.zephyrsoft.util.gui.ImagePanel.java

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/*
 * This file is part of the Song Database (SDB).
 *
 * SDB 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 2 of the License, or
 * (at your option) any later version.
 *
 * SDB 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 SDB. If not, see <http://www.gnu.org/licenses/>.
 */
package org.zephyrsoft.util.gui;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.JPanel;
import javax.swing.border.Border;
import org.apache.commons.lang3.Validate;

/**
 * Display an image at the right scale to make it fit exactly into the container.
 * 
 * @author Scott Carpenter (scottc at movingtofreedom dot org)
 * @author Mathis Dirksen-Thedens
 */
public class ImagePanel extends JPanel {

    private static final long serialVersionUID = -1157676441033085598L;

    private Image image;
    private int lastUsedHeight = -1;
    private int lastUsedWidth = -1;
    private Image scaledImage;

    private float width;
    private float height;
    private int x;
    private int y;

    public ImagePanel(Image image) {
        this.image = image;

        // workaround for Nimbus L&F:
        setOpaque(false);
        setBackground(new Color(0, 0, 0, 0));
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        if (mustRescaleImage()) {
            calculateScaledImage();
        }
        if (scaledImage != null) {
            g.drawImage(scaledImage, x + (int) ((width - scaledImage.getWidth(null)) / 2),
                    y + (int) ((height - scaledImage.getHeight(null)) / 2), this);
        } else {
            throw new IllegalStateException("the scaled image was not computed");
        }
    }

    private boolean mustRescaleImage() {
        return lastUsedHeight != getHeight() || lastUsedWidth != getWidth();
    }

    private void calculateScaledImage() {
        Validate.notNull(image, "original image may not be null");

        // use floats so division below won't round
        float imageWidth = image.getWidth(null);
        float imageHeight = image.getHeight(null);
        width = this.getWidth();
        height = this.getHeight();
        x = 0;
        y = 0;

        // take special care for a border which might exist
        Border border = getBorder();
        if (border != null) {
            x = border.getBorderInsets(this).left;
            y = border.getBorderInsets(this).top;
            width -= x;
            width -= border.getBorderInsets(this).right;
            height -= y;
            height -= border.getBorderInsets(this).bottom;
        }

        if (width < imageWidth || height < imageHeight) {
            // decide which value should be taken to rescale the image
            if ((width / height) > (imageWidth / imageHeight)) {
                imageWidth = -1;
                imageHeight = height;
            } else {
                imageWidth = width;
                imageHeight = -1;
            }

            // prevent errors if panel is 0 wide or high
            if (imageWidth == 0) {
                imageWidth = -1;
            }
            if (imageHeight == 0) {
                imageHeight = -1;
            }

            scaledImage = image.getScaledInstance(Float.valueOf(imageWidth).intValue(),
                    Float.valueOf(imageHeight).intValue(), Image.SCALE_DEFAULT);

        } else {
            scaledImage = image;
        }
    }

}