Package com.itextpdf.layout

Class Canvas

  • All Implemented Interfaces:
    IPropertyContainer, java.io.Closeable, java.lang.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 Detail

      • 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 Detail

      • 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 Detail

      • 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.

      • initPdfCanvasOrThrowIfPageIsFlushed

        private static PdfCanvas initPdfCanvasOrThrowIfPageIsFlushed​(PdfPage page)