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## 9.13. Render Page Sections to PNG

The reasons for testing a particular region of a PDF page are described in section 3.21: “Layout - in Page Regions”. To find the coordinates of the area you want to test, PDFUnit provides the small utility `RenderPdfPageRegionToImage`. Choose the width, height and the position of the upper left corner and the corresponding region is then extracted into a file. Verify this file then “by eye” and vary the parameters until you got the right region. Once you have found the correct coordinates for your region, use those parameters in your PDFUnit test.

### Program Start

    ::
    :: Render a part of a PDF page into an image file
    ::

    @echo off
    setlocal
    set CLASSPATH=./lib/aspectj-1.8.7/*;%CLASSPATH%
    set CLASSPATH=./lib/commons-logging-1.2/*;%CLASSPATH%
    set CLASSPATH=./lib/pdfbox-2.0.0/*;%CLASSPATH%
    set CLASSPATH=./lib/pdfunit-2016.05/*;%CLASSPATH%

    set TOOL=com.pdfunit.tools.RenderPdfPageRegionToImage
    set OUT_DIR=./tmp
    set PAGENUMBER=1
    set IN_FILE=documentForTextClipping.pdf
    set PASSWD=

    :: Put these values into your test code:
    :: Values in millimeter:
    set UPPERLEFTX=17
    set UPPERLEFTY=45
    set WIDTH=60
    set HEIGHT=9

    java  %TOOL%  %IN_FILE%  %PAGENUMBER%  %OUT_DIR%
          %FORMATUNIT%  %UPPERLEFTX%  %UPPERLEFTY%  %WIDTH%  %HEIGHT%  %PASSWD%
    endlocal

| The linebreak in this listing is placed here only for documentation purposes.

The 4 values that define a page region have to have the unit millimeter (mm).

### Input

The upper part of the input file `documentForTextClipping.pdf` contains the text: “ `Content on first page.` ”

### Output

The generated image file has to be checked.

The name of the generated PNG includes the area’s coordinates. Because PDFUnit and the utility program `RenderPdfPageRegionToImage` use the same algorithm, you can use the parameter values from the script for your test. And later, you can derive them from the file name:

    #
    # Parameters from filename:
    #

    _rendered_documentForTextClipping_page-1_area-50-130-170-25.out.png
                                                   |  |   |   |
                                                   |  |   |   +- height
                                                   |  |   +- width
                                                   |  +- upperLeftY
                                                   +- upperLeftX

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