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Asked: 2026-06-12T09:00:59+00:00

I’ve written a script to use ImageMagick to convert PDFs into JPGs for each

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I’ve written a script to use ImageMagick to convert PDFs into JPGs for each page, along with resizing/etc.

Where it gets slightly more tricky is some PDFs have the middle two-page spread as “one page” – so it is extra wide. Is there ANY way to “detect” this and crop the left and right sides, as two separate pages?

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  1. Editorial Team

    Assuming you want to use ImageMagick (and only ImageMagick) for this: that can’t be done. ImageMagick cannot process PDF input all by itself. It has to make use of Ghostscript anyway, so without a local Ghostscript installation it won’t work. (You will not necessarily see Ghostscript at work while you feed PDF input to ImageMagick, unless you add a -verbose to its command line, because ImageMagick’s delegation of the job to Ghostscript happens behind your back…)

    Your question has two parts:

    • "Is there a way to "detect" extra wide pages, like the center spreads?"
    • "Is there a way to crop the left and right parts from center spreads as two separate pages?"

    Detect page sizes

    You can use ImageMagick’s identify to detect the page sizes of a PDF.

    Just run the most simple command:

    identify multipage.pdf

    The output will be s.th. like

    multipage.pdf[0] PDF 595x792 595x792+0+0 16-bit Bilevel DirectClass 59.5KB 0.000u 0:00.000
multipage.pdf[1] PDF 595x792 595x792+0+0 16-bit Bilevel DirectClass 59.5KB 0.000u 0:00.000
multipage.pdf[2] PDF 595x792 595x792+0+0 16-bit Bilevel DirectClass 59.5KB 0.000u 0:00.000
multipage.pdf[3] PDF 595x792 595x792+0+0 16-bit Bilevel DirectClass 59.5KB 0.000u 0:00.000

    The output’s page count is 0-based. So [0] indicates the first page, [1] the second page, etc.

    To customize the output a bit better, you could do this:

    identify -format '%f, page %s + 1: %W x %H\n' multipage.pdf

    and get

    multipage.pdf, page  0 + 1: 595 x 792
multipage.pdf, page  1 + 1: 595 x 792
multipage.pdf, page  2 + 1: 595 x 792
multipage.pdf, page  3 + 1: 595 x 792

    For a double-spread page the respective output should be 1190 x 792 or similar.

    However, be warned: to use ImageMagick for querying the page sizes of PDF files is veeeery slow. Therefor, better use a different tool for this sub-task: pdfinfo. This will be faster by several orders of magnitude:

    pdfinfo -f 1 -l 1000 -box multipage.pdf

    will output

    Pages:          4
Page    1 size: 595 x 792 pts
Page    1 rot:  0
Page    2 size: 595 x 792 pts
Page    2 rot:  0
Page    3 size: 595 x 792 pts
Page    3 rot:  0
Page    4 size: 595 x 792 pts
Page    4 rot:  0

    If you need additional info about the pages’ ArtBox, TrimBox, BleedBox and CropBox values, just add -box to the commandline.

    As I said: pdfinfo is significantly faster in identifying page sizes for PDFs than ImageMagick is. Use the right tool for the job.

    Crop left and right parts of a page

    Now that you have identified the large double-spread page, you could use one of the following methods (based on Ghostscript) to split down the pages in the middle:

    Adapting the method described in above links will result in 2 PDF pages that still contain all their original vector and font info.

    Alternatively, you can use ImageMagick. Assuming your ‘double-spread’ page is of dimension 1190×842 pt, based on A4 (595×842 pt), and assuming it is page 16 (which translates to [15] for ImageMagick) inside an original PDF, your convert commands could be s.th. like:

    convert  multipage.pdf[15]  -crop 595x842+0+0    page16-left.png
convert  multipage.pdf[15]  -crop 595x842+595+0  page16-right.png

    The result gives you two raster images.

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