Package com.itextpdf.io.util

Class GhostscriptHelper

  • public class GhostscriptHelper
extends java.lang.Object
    A utility class that is used as an interface to run 3rd-party tool Ghostscript. Ghostscript is an interpreter for the PostScript language and PDF files, it allows to render them as images.

    The Ghostscript needs to be installed independently on the system. This class provides a convenient way to run it by passing a terminal command. The command can either be specified explicitly or by a mean of environment variable GHOSTSCRIPT_ENVIRONMENT_VARIABLE.

    • Field Detail

      • GHOSTSCRIPT_ENVIRONMENT_VARIABLE

        public static final java.lang.String GHOSTSCRIPT_ENVIRONMENT_VARIABLE
        The name of the environment variable with the command to execute Ghostscript operations.
        See Also:
        Constant Field Values

      • TEMP_FILE_PREFIX

        private static final java.lang.String TEMP_FILE_PREFIX
        See Also:
        Constant Field Values

      • RENDERED_IMAGE_EXTENSION

        private static final java.lang.String RENDERED_IMAGE_EXTENSION
        See Also:
        Constant Field Values

      • GHOSTSCRIPT_PARAMS

        private static final java.lang.String GHOSTSCRIPT_PARAMS
        See Also:
        Constant Field Values

      • PAGE_NUMBER_PATTERN

        private static final java.lang.String PAGE_NUMBER_PATTERN
        See Also:
        Constant Field Values

      • PAGE_LIST_REGEX

        private static final java.util.regex.Pattern PAGE_LIST_REGEX

      • gsExec

        private java.lang.String gsExec

    • Constructor Detail

      • GhostscriptHelper

        public GhostscriptHelper()
        Creates new instance that will rely on Ghostscript execution command defined by GHOSTSCRIPT_ENVIRONMENT_VARIABLE environment variable.

      • GhostscriptHelper

        public GhostscriptHelper​(java.lang.String newGsExec)
        Creates new instance that will rely on Ghostscript execution command defined as passed argument.
        Parameters:
        newGsExec - the Ghostscript execution command; if null - environment variables will be used instead

    • Method Detail

      • getCliExecutionCommand

        public java.lang.String getCliExecutionCommand()
        Returns a command that is used to run the utility. This command doesn't contain command parameters. Parameters are added on specific methods invocation.
        Returns:
        a string command

      • runGhostScriptImageGeneration

        public void runGhostScriptImageGeneration​(java.lang.String pdf,
                                          java.lang.String outDir,
                                          java.lang.String image)
                                   throws java.io.IOException,
                                          java.lang.InterruptedException
        Runs Ghostscript to render the PDF's pages as PNG images.

        Note, that this method may create temporary directory and files.

        Parameters:
        pdf - Path to the PDF file to be rendered
        outDir - Path to the output directory, in which the rendered pages will be stored
        image - String which defines the name of the resultant images. This string will be concatenated with the number of the rendered page from the start of the PDF in "-%03d" format, e.g. "-011" for the eleventh rendered page and so on. This number may not correspond to the actual page number: for example, if the passed pageList equals to "5,3", then images with postfixes "-001.png" and "-002.png" will be created: the former for the third page, the latter for the fifth page. "%" sign in the passed name is prohibited.
        Throws:
        java.io.IOException - if there are file's reading/writing issues
        java.lang.InterruptedException - if there is thread interruption while executing GhostScript.

      • runGhostScriptImageGeneration

        public void runGhostScriptImageGeneration​(java.lang.String pdf,
                                          java.lang.String outDir,
                                          java.lang.String image,
                                          java.lang.String pageList)
                                   throws java.io.IOException,
                                          java.lang.InterruptedException
        Runs Ghostscript to render the PDF's pages as PNG images.

        Note, that this method may create temporary directory and files.

        Parameters:
        pdf - Path to the PDF file to be rendered
        outDir - Path to the output directory, in which the rendered pages will be stored
        image - String which defines the name of the resultant images. This string will be concatenated with the number of the rendered page from the start of the PDF in "-%03d" format, e.g. "-011" for the eleventh rendered page and so on. This number may not correspond to the actual page number: for example, if the passed pageList equals to "5,3", then images with postfixes "-001.png" and "-002.png" will be created: the former for the third page, the latter for the fifth page. "%" sign in the passed name is prohibited.
        pageList - String with numbers of the required pages to be rendered as images. This string should be formatted as a string with numbers, separated by commas, without whitespaces. Can be null, if it is required to render all the PDF's pages.
        Throws:
        java.io.IOException - if there are file's reading/writing issues
        java.lang.InterruptedException - if there is thread interruption while executing GhostScript.

      • validatePageList

        static boolean validatePageList​(java.lang.String pageList)

      • validateImageFilePattern

        static boolean validateImageFilePattern​(java.lang.String imageFilePattern)

      • formatImageNumber

        static java.lang.String formatImageNumber​(int pageNumber)