Java tutorial
/******************************************************************************* * Copyright (c) 2004 Chengdong Li : cdli@ccs.uky.edu * All rights reserved. This program and the accompanying materials * are made available under the terms of the Common Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/cpl-v10.html *******************************************************************************/ package uky.article.imageviewer.views; import java.awt.geom.AffineTransform; import java.io.IOException; import java.io.InputStream; import java.net.URL; import org.apache.commons.io.IOUtils; import org.eclipse.swt.SWT; import org.eclipse.swt.events.ControlAdapter; import org.eclipse.swt.events.ControlEvent; import org.eclipse.swt.events.PaintEvent; import org.eclipse.swt.events.PaintListener; import org.eclipse.swt.events.SelectionAdapter; import org.eclipse.swt.events.SelectionEvent; import org.eclipse.swt.graphics.GC; import org.eclipse.swt.graphics.Image; import org.eclipse.swt.graphics.ImageData; import org.eclipse.swt.graphics.Rectangle; import org.eclipse.swt.widgets.Canvas; import org.eclipse.swt.widgets.Composite; import org.eclipse.swt.widgets.FileDialog; import org.eclipse.swt.widgets.ScrollBar; import okhttp3.OkHttpClient; import okhttp3.Request; import okhttp3.Response; import us.nineworlds.xstreamer.core.httpclient.OKHttpClient; /** * A scrollable image canvas that extends org.eclipse.swt.graphics.Canvas. * <p/> * It requires Eclipse (version >= 2.1) on Win32/win32; Linux/gtk; MacOSX/carbon. * <p/> * This implementation using the pure SWT, no UI AWT package is used. For * convenience, I put everything into one class. However, the best way to * implement this is to use inheritance to create multiple hierarchies. * * @author Chengdong Li: cli4@uky.edu */ public class SWTImageCanvas extends Canvas { /* zooming rates in x and y direction are equal.*/ final float ZOOMIN_RATE = 1.1f; /* zoomin rate */ final float ZOOMOUT_RATE = 0.9f; /* zoomout rate */ private Image sourceImage; /* original image */ private Image screenImage; /* screen image */ private AffineTransform transform = new AffineTransform(); private String currentDir = ""; /* remembering file open directory */ public SWTImageCanvas(final Composite parent) { this(parent, SWT.NULL); } /** * Constructor for ScrollableCanvas. * @param parent the parent of this control. * @param style the style of this control. */ public SWTImageCanvas(final Composite parent, int style) { super(parent, style | SWT.BORDER | SWT.V_SCROLL | SWT.H_SCROLL | SWT.NO_BACKGROUND); addControlListener(new ControlAdapter() { /* resize listener. */ @Override public void controlResized(ControlEvent event) { syncScrollBars(); } }); addPaintListener(new PaintListener() { /* paint listener. */ @Override public void paintControl(final PaintEvent event) { paint(event.gc); } }); initScrollBars(); } /** * Dispose the garbage here */ @Override public void dispose() { if (sourceImage != null && !sourceImage.isDisposed()) { sourceImage.dispose(); } if (screenImage != null && !screenImage.isDisposed()) { screenImage.dispose(); } } /* Paint function */ private void paint(GC gc) { Rectangle clientRect = getClientArea(); /* Canvas' painting area */ if (sourceImage != null) { Rectangle imageRect = SWT2Dutil.inverseTransformRect(transform, clientRect); int gap = 2; /* find a better start point to render */ imageRect.x -= gap; imageRect.y -= gap; imageRect.width += 2 * gap; imageRect.height += 2 * gap; Rectangle imageBound = sourceImage.getBounds(); imageRect = imageRect.intersection(imageBound); Rectangle destRect = SWT2Dutil.transformRect(transform, imageRect); if (screenImage != null) screenImage.dispose(); screenImage = new Image(getDisplay(), clientRect.width, clientRect.height); GC newGC = new GC(screenImage); newGC.setClipping(clientRect); newGC.drawImage(sourceImage, imageRect.x, imageRect.y, imageRect.width, imageRect.height, destRect.x, destRect.y, destRect.width, destRect.height); newGC.dispose(); gc.drawImage(screenImage, 0, 0); } else { gc.setClipping(clientRect); gc.fillRectangle(clientRect); initScrollBars(); } } /* Initalize the scrollbar and register listeners. */ private void initScrollBars() { ScrollBar horizontal = getHorizontalBar(); horizontal.setEnabled(false); horizontal.addSelectionListener(new SelectionAdapter() { @Override public void widgetSelected(SelectionEvent event) { scrollHorizontally((ScrollBar) event.widget); } }); ScrollBar vertical = getVerticalBar(); vertical.setEnabled(false); vertical.addSelectionListener(new SelectionAdapter() { @Override public void widgetSelected(SelectionEvent event) { scrollVertically((ScrollBar) event.widget); } }); } /* Scroll horizontally */ private void scrollHorizontally(ScrollBar scrollBar) { if (sourceImage == null) return; AffineTransform af = transform; double tx = af.getTranslateX(); double select = -scrollBar.getSelection(); af.preConcatenate(AffineTransform.getTranslateInstance(select - tx, 0)); transform = af; syncScrollBars(); } /* Scroll vertically */ private void scrollVertically(ScrollBar scrollBar) { if (sourceImage == null) return; AffineTransform af = transform; double ty = af.getTranslateY(); double select = -scrollBar.getSelection(); af.preConcatenate(AffineTransform.getTranslateInstance(0, select - ty)); transform = af; syncScrollBars(); } /** * Source image getter. * @return sourceImage. */ public Image getSourceImage() { return sourceImage; } /** * Synchronize the scrollbar with the image. If the transform is out * of range, it will correct it. This function considers only following * factors :<b> transform, image size, client area</b>. */ public void syncScrollBars() { if (sourceImage == null) { redraw(); return; } AffineTransform af = transform; double sx = af.getScaleX(), sy = af.getScaleY(); double tx = af.getTranslateX(), ty = af.getTranslateY(); if (tx > 0) tx = 0; if (ty > 0) ty = 0; ScrollBar horizontal = getHorizontalBar(); horizontal.setIncrement(getClientArea().width / 100); horizontal.setPageIncrement(getClientArea().width); Rectangle imageBound = sourceImage.getBounds(); int cw = getClientArea().width, ch = getClientArea().height; if (imageBound.width * sx > cw) { /* image is wider than client area */ horizontal.setMaximum((int) (imageBound.width * sx)); horizontal.setEnabled(true); if (((int) -tx) > horizontal.getMaximum() - cw) tx = -horizontal.getMaximum() + cw; } else { /* image is narrower than client area */ horizontal.setEnabled(false); tx = (cw - imageBound.width * sx) / 2; //center if too small. } horizontal.setSelection((int) (-tx)); horizontal.setThumb((getClientArea().width)); ScrollBar vertical = getVerticalBar(); vertical.setIncrement(getClientArea().height / 100); vertical.setPageIncrement((getClientArea().height)); if (imageBound.height * sy > ch) { /* image is higher than client area */ vertical.setMaximum((int) (imageBound.height * sy)); vertical.setEnabled(true); if (((int) -ty) > vertical.getMaximum() - ch) ty = -vertical.getMaximum() + ch; } else { /* image is less higher than client area */ vertical.setEnabled(false); ty = (ch - imageBound.height * sy) / 2; //center if too small. } vertical.setSelection((int) (-ty)); vertical.setThumb((getClientArea().height)); /* update transform. */ af = AffineTransform.getScaleInstance(sx, sy); af.preConcatenate(AffineTransform.getTranslateInstance(tx, ty)); transform = af; redraw(); } /** * Reload image from a file * @param filename image file * @return swt image created from image file */ public Image loadImage(String filename) { disposeImage(); sourceImage = new Image(getDisplay(), filename); showOriginal(); return sourceImage; } private void disposeImage() { if (sourceImage != null && !sourceImage.isDisposed()) { sourceImage.dispose(); sourceImage = null; } } public Image loadImage(InputStream inputStream) { disposeImage(); sourceImage = new Image(getDisplay(), inputStream); IOUtils.closeQuietly(inputStream); showOriginal(); return sourceImage; } public Image loadImage(URL url) { disposeImage(); OkHttpClient client = OKHttpClient.getInstance(); Request request = new Request.Builder().url(url).build(); try { Response response = client.newCall(request).execute(); sourceImage = new Image(getDisplay(), response.body().byteStream()); } catch (IOException e) { e.printStackTrace(); } showOriginal(); return sourceImage; } /** * Call back funtion of button "open". Will open a file dialog, and choose * the image file. It supports image formats supported by Eclipse. */ public void onFileOpen() { FileDialog fileChooser = new FileDialog(getShell(), SWT.OPEN); fileChooser.setText("Open image file"); fileChooser.setFilterPath(currentDir); fileChooser.setFilterExtensions(new String[] { "*.gif; *.jpg; *.png; *.ico; *.bmp" }); fileChooser.setFilterNames(new String[] { "SWT image" + " (gif, jpeg, png, ico, bmp)" }); String filename = fileChooser.open(); if (filename != null) { loadImage(filename); currentDir = fileChooser.getFilterPath(); } } /** * Get the image data. (for future use only) * @return image data of canvas */ public ImageData getImageData() { return sourceImage.getImageData(); } /** * Reset the image data and update the image * @param data image data to be set */ public void setImageData(ImageData data) { if (sourceImage != null) sourceImage.dispose(); if (data != null) sourceImage = new Image(getDisplay(), data); syncScrollBars(); } /** * Fit the image onto the canvas */ public void fitCanvas() { if (sourceImage == null) return; Rectangle imageBound = sourceImage.getBounds(); Rectangle destRect = getClientArea(); double sx = (double) destRect.width / (double) imageBound.width; double sy = (double) destRect.height / (double) imageBound.height; double s = Math.min(sx, sy); double dx = 0.5 * destRect.width; double dy = 0.5 * destRect.height; centerZoom(dx, dy, s, new AffineTransform()); } /** * Show the image with the original size */ public void showOriginal() { if (sourceImage == null) return; transform = new AffineTransform(); syncScrollBars(); } /** * Perform a zooming operation centered on the given point * (dx, dy) and using the given scale factor. * The given AffineTransform instance is preconcatenated. * @param dx center x * @param dy center y * @param scale zoom rate * @param af original affinetransform */ public void centerZoom(double dx, double dy, double scale, AffineTransform af) { af.preConcatenate(AffineTransform.getTranslateInstance(-dx, -dy)); af.preConcatenate(AffineTransform.getScaleInstance(scale, scale)); af.preConcatenate(AffineTransform.getTranslateInstance(dx, dy)); transform = af; syncScrollBars(); } /** * Zoom in around the center of client Area. */ public void zoomIn() { if (sourceImage == null) return; Rectangle rect = getClientArea(); int w = rect.width, h = rect.height; double dx = ((double) w) / 2; double dy = ((double) h) / 2; centerZoom(dx, dy, ZOOMIN_RATE, transform); } /** * Zoom out around the center of client Area. */ public void zoomOut() { if (sourceImage == null) return; Rectangle rect = getClientArea(); int w = rect.width, h = rect.height; double dx = ((double) w) / 2; double dy = ((double) h) / 2; centerZoom(dx, dy, ZOOMOUT_RATE, transform); } }