Java tutorial
/* This file is part of the iText (R) project. Copyright (c) 1998-2019 iText Group NV Authors: Bruno Lowagie, Paulo Soares, 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 ITEXT GROUP. ITEXT GROUP 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, or download the license from the following URL: http://itextpdf.com/terms-of-use/ 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. In accordance with Section 7(b) of the GNU Affero General Public License, a covered work must retain the producer line in every PDF that is created or manipulated using iText. 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 iText software without disclosing the source code of your own applications. These activities include: offering paid services to customers as an ASP, serving PDFs on the fly in a web application, shipping iText with a closed source product. For more information, please contact iText Software Corp. at this address: sales@itextpdf.com */ package com.itextpdf.layout; import com.itextpdf.io.LogMessageConstant; import com.itextpdf.kernel.PdfException; import com.itextpdf.kernel.geom.Rectangle; import com.itextpdf.kernel.pdf.PdfDocument; import com.itextpdf.kernel.pdf.PdfPage; import com.itextpdf.kernel.pdf.canvas.PdfCanvas; import com.itextpdf.kernel.pdf.xobject.PdfFormXObject; import com.itextpdf.layout.element.IElement; import com.itextpdf.layout.renderer.CanvasRenderer; import com.itextpdf.layout.renderer.IRenderer; import com.itextpdf.layout.renderer.RootRenderer; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * This class is used for adding content directly onto a specified {@link PdfCanvas}. * {@link Canvas} does not know the concept of a page, so it can't reflow to a 'next' {@link Canvas}. * * This class effectively acts as a bridge between the high-level <em>layout</em> * API and the low-level <em>kernel</em> API. */ public class Canvas extends RootElement<Canvas> { protected PdfCanvas pdfCanvas; protected Rectangle rootArea; /** * Is initialized and used only when Canvas element autotagging is enabled, see {@link #enableAutoTagging(PdfPage)}. * It is also used to determine if autotagging is enabled. */ protected PdfPage page; private boolean isCanvasOfPage; /** * Creates a new Canvas to manipulate a specific page content stream. The given page shall not be flushed: * drawing on flushed pages is impossible because their content is already written to the output stream. * Use this constructor to be able to add {@link com.itextpdf.layout.element.Link} elements on it * (using any other constructor would result in inability to add PDF annotations, based on which, for example, links work). * <p> * If the {@link PdfDocument#isTagged()} is true, using this constructor would automatically enable * the tagging for the content. Regarding tagging the effect is the same as using {@link #enableAutoTagging(PdfPage)}. * * @param page the page on which this canvas will be rendered, shall not be flushed (see {@link PdfPage#isFlushed()}). * @param rootArea the maximum area that the Canvas may write upon */ public Canvas(PdfPage page, Rectangle rootArea) { this(initPdfCanvasOrThrowIfPageIsFlushed(page), page.getDocument(), rootArea); this.enableAutoTagging(page); this.isCanvasOfPage = true; } /** * Creates a new Canvas to manipulate a specific document and content stream, which might be for example a page * or {@link PdfFormXObject} stream. * * @param pdfCanvas the low-level content stream writer * @param pdfDocument the document that the resulting content stream will be written to * @param rootArea the maximum area that the Canvas may write upon */ public Canvas(PdfCanvas pdfCanvas, PdfDocument pdfDocument, Rectangle rootArea) { super(); this.pdfDocument = pdfDocument; this.pdfCanvas = pdfCanvas; this.rootArea = rootArea; } /** * Creates a new Canvas to manipulate a specific document and page. * * @param pdfCanvas The low-level content stream writer * @param pdfDocument The document that the resulting content stream will be written to * @param rootArea The maximum area that the Canvas may write upon * @param immediateFlush Whether to flush the canvas immediately after operations, false otherwise */ public Canvas(PdfCanvas pdfCanvas, PdfDocument pdfDocument, Rectangle rootArea, boolean immediateFlush) { this(pdfCanvas, pdfDocument, rootArea); this.immediateFlush = immediateFlush; } /** * Creates a new Canvas to manipulate a specific {@link PdfFormXObject}. * * @param formXObject the form * @param pdfDocument the document that the resulting content stream will be written to */ public Canvas(PdfFormXObject formXObject, PdfDocument pdfDocument) { this(new PdfCanvas(formXObject, pdfDocument), pdfDocument, formXObject.getBBox().toRectangle()); } /** * Gets the {@link PdfDocument} for this canvas. * @return the document that the resulting content stream will be written to */ public PdfDocument getPdfDocument() { return pdfDocument; } /** * Gets the root area rectangle. * @return the maximum area that the Canvas may write upon */ public Rectangle getRootArea() { return rootArea; } /** * Gets the {@link PdfCanvas}. * @return the low-level content stream writer */ public PdfCanvas getPdfCanvas() { return pdfCanvas; } /** * Sets the {@link IRenderer} for this Canvas. * * @param canvasRenderer a renderer specific for canvas operations */ public void setRenderer(CanvasRenderer canvasRenderer) { this.rootRenderer = canvasRenderer; } /** * The page on which this canvas will be rendered. * @return the specified {@link PdfPage} instance, might be null if this the page was not set. */ public PdfPage getPage() { return page; } /** * Enables canvas content autotagging. By default it is disabled. * @param page the page, on which this canvas will be rendered. */ public void enableAutoTagging(PdfPage page) { if (isCanvasOfPage() && this.page != page) { Logger logger = LoggerFactory.getLogger(Canvas.class); logger.error(LogMessageConstant.PASSED_PAGE_SHALL_BE_ON_WHICH_CANVAS_WILL_BE_RENDERED); } this.page = page; } /** * @return true if autotagging of canvas content is enabled. Default value - false. */ public boolean isAutoTaggingEnabled() { return page != null; } /** * Defines if the canvas is exactly the direct content of the page. This is known definitely only if * this instance was created by {@link Canvas#Canvas(PdfPage, Rectangle)} constructor overload, * otherwise this method returns false. * @return true if the canvas on which this instance performs drawing is directly the canvas of the page; * false if the instance of this class was created not with {@link Canvas#Canvas(PdfPage, Rectangle)} constructor overload. */ public boolean isCanvasOfPage() { return isCanvasOfPage; } /** * Performs an entire recalculation of the element flow on the canvas, * taking into account all its current child elements. May become very * resource-intensive for large documents. * * Do not use when you have set {@link #immediateFlush} to <code>true</code>. */ public void relayout() { if (immediateFlush) { throw new IllegalStateException("Operation not supported with immediate flush"); } IRenderer nextRelayoutRenderer = rootRenderer != null ? rootRenderer.getNextRenderer() : null; if (nextRelayoutRenderer == null || !(nextRelayoutRenderer instanceof RootRenderer)) { nextRelayoutRenderer = new CanvasRenderer(this, immediateFlush); } rootRenderer = (RootRenderer) nextRelayoutRenderer; for (IElement element : childElements) { createAndAddRendererSubTree(element); } } /** * Forces all registered renderers (including child element renderers) to * flush their contents to the content stream. */ public void flush() { rootRenderer.flush(); } /** * Closes the {@link Canvas}. Although not completely necessary in all cases, it is still recommended to call this * method when you are done working with {@link Canvas} object, as due to some properties set there might be some * 'hanging' elements, which are waiting other elements to be added and processed. {@link #close()} tells the * {@link Canvas} that no more elements will be added and it is time to finish processing all the elements. */ @Override public void close() { if (rootRenderer != null) { rootRenderer.close(); } } @Override protected RootRenderer ensureRootRendererNotNull() { if (rootRenderer == null) rootRenderer = new CanvasRenderer(this, immediateFlush); return rootRenderer; } private static PdfCanvas initPdfCanvasOrThrowIfPageIsFlushed(PdfPage page) { if (page.isFlushed()) { throw new PdfException(PdfException.CannotDrawElementsOnAlreadyFlushedPages); } return new PdfCanvas(page); } }