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com.itextpdf.layout.Canvas Maven / Gradle / Ivy
/*
This file is part of the iText (R) project.
Copyright (c) 1998-2024 Apryse Group NV
Authors: Apryse Software.
This program is offered under a commercial and under the AGPL license.
For commercial licensing, contact us at https://itextpdf.com/sales. For AGPL licensing, see below.
AGPL licensing:
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
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 layout
* API and the low-level kernel API.
*/
public class Canvas extends RootElement {
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).
*
* 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), rootArea);
this.enableAutoTagging(page);
this.isCanvasOfPage = true;
}
/**
* Creates a new Canvas to manipulate a specific content stream, which might be for example a page
* or {@link PdfFormXObject} stream.
*
* @param pdfCanvas the low-level content stream writer
* @param rootArea the maximum area that the Canvas may write upon
*/
public Canvas(PdfCanvas pdfCanvas, Rectangle rootArea) {
super();
this.pdfDocument = pdfCanvas.getDocument();
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 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, Rectangle rootArea, boolean immediateFlush) {
this(pdfCanvas, 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), 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(IoLogMessageConstant.PASSED_PAGE_SHALL_BE_ON_WHICH_CANVAS_WILL_BE_RENDERED);
}
this.page = page;
this.pdfCanvas.setDrawingOnPage(this.isAutoTaggingEnabled());
}
/**
* @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 true.
*/
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(LayoutExceptionMessageConstant.CANNOT_DRAW_ELEMENTS_ON_ALREADY_FLUSHED_PAGES);
}
return new PdfCanvas(page);
}
}
