Class Canvas

java.lang.Object
com.itextpdf.commons.actions.sequence.AbstractIdentifiableElement
com.itextpdf.layout.ElementPropertyContainer<Canvas>
com.itextpdf.layout.RootElement<Canvas>
com.itextpdf.layout.Canvas
All Implemented Interfaces:
IPropertyContainer, Closeable, AutoCloseable
public class Canvas extends RootElement<Canvas>
This class is used for adding content directly onto a specified PdfCanvas. Canvas does not know the concept of a page, so it can't reflow to a 'next' Canvas. This class effectively acts as a bridge between the high-level layout API and the low-level kernel API.

  • Field Details

    • pdfCanvas

      protected PdfCanvas pdfCanvas

    • rootArea

      protected Rectangle rootArea

    • page

      protected PdfPage page
      Is initialized and used only when Canvas element autotagging is enabled, see enableAutoTagging(PdfPage). It is also used to determine if autotagging is enabled.

    • isCanvasOfPage

      private boolean isCanvasOfPage

  • Constructor Details

    • Canvas

      public Canvas(PdfPage page, Rectangle rootArea)
      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 elements on it (using any other constructor would result in inability to add PDF annotations, based on which, for example, links work).

      If the PdfDocument.isTagged() is true, using this constructor would automatically enable the tagging for the content. Regarding tagging the effect is the same as using enableAutoTagging(PdfPage).

      Parameters:
      page - the page on which this canvas will be rendered, shall not be flushed (see PdfObjectWrapper.isFlushed()).
      rootArea - the maximum area that the Canvas may write upon

    • Canvas

      public Canvas(PdfCanvas pdfCanvas, Rectangle rootArea)
      Creates a new Canvas to manipulate a specific content stream, which might be for example a page or PdfFormXObject stream.
      Parameters:
      pdfCanvas - the low-level content stream writer
      rootArea - the maximum area that the Canvas may write upon

    • Canvas

      public Canvas(PdfCanvas pdfCanvas, Rectangle rootArea, boolean immediateFlush)
      Creates a new Canvas to manipulate a specific document and page.
      Parameters:
      pdfCanvas - The low-level content stream writer
      rootArea - The maximum area that the Canvas may write upon
      immediateFlush - Whether to flush the canvas immediately after operations, false otherwise

    • Canvas

      public Canvas(PdfFormXObject formXObject, PdfDocument pdfDocument)
      Creates a new Canvas to manipulate a specific PdfFormXObject.
      Parameters:
      formXObject - the form
      pdfDocument - the document that the resulting content stream will be written to

  • Method Details

    • getPdfDocument

      public PdfDocument getPdfDocument()
      Gets the PdfDocument for this canvas.
      Returns:
      the document that the resulting content stream will be written to

    • getRootArea

      public Rectangle getRootArea()
      Gets the root area rectangle.
      Returns:
      the maximum area that the Canvas may write upon

    • getPdfCanvas

      public PdfCanvas getPdfCanvas()
      Gets the PdfCanvas.
      Returns:
      the low-level content stream writer

    • setRenderer

      public void setRenderer(CanvasRenderer canvasRenderer)
      Sets the IRenderer for this Canvas.
      Parameters:
      canvasRenderer - a renderer specific for canvas operations

    • getPage

      public PdfPage getPage()
      The page on which this canvas will be rendered.
      Returns:
      the specified PdfPage instance, might be null if this the page was not set.

    • enableAutoTagging

      public void enableAutoTagging(PdfPage page)
      Enables canvas content autotagging. By default it is disabled.
      Parameters:
      page - the page, on which this canvas will be rendered.

    • isAutoTaggingEnabled

      public boolean isAutoTaggingEnabled()
      Returns:
      true if autotagging of canvas content is enabled. Default value - false.

    • isCanvasOfPage

      public boolean isCanvasOfPage()
      Defines if the canvas is exactly the direct content of the page. This is known definitely only if this instance was created by Canvas(PdfPage, Rectangle) constructor overload, otherwise this method returns false.
      Returns:
      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 Canvas(PdfPage, Rectangle) constructor overload.

    • relayout

      public void relayout()
      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 RootElement.immediateFlush to true.

    • flush

      public void flush()
      Forces all registered renderers (including child element renderers) to flush their contents to the content stream.

    • close

      public void close()
      Closes the Canvas. Although not completely necessary in all cases, it is still recommended to call this method when you are done working with Canvas object, as due to some properties set there might be some 'hanging' elements, which are waiting other elements to be added and processed. close() tells the Canvas that no more elements will be added and it is time to finish processing all the elements.

    • ensureRootRendererNotNull

      protected RootRenderer ensureRootRendererNotNull()
      Specified by:
      ensureRootRendererNotNull in class RootElement<Canvas>

    • initPdfCanvasOrThrowIfPageIsFlushed

      private static PdfCanvas initPdfCanvasOrThrowIfPageIsFlushed(PdfPage page)