Active3 years, 2 months ago
A: Starting in PDF Studio 12 (Pro) and above, you can deskew (straighten) a document on scan dialog. On scan dialog, make sure to check the “Auto deskew images” checkbox. See below for the scan dialog when scanning with WIA, TWAIN and SANE.
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Which free software can I use to deskew scanned images
Which free software can I use to deskew scanned images
I have several PDFs made up of book pages' scans. The scans are made from two pages at a time and some of these scans are skewed, making text appear slightly tilted.
I'm looking for a tool that could allow me to do an automatic optimization by deskewing the scans without losing readability. I've found the GPL software Briss to crop the scans in order to have a 1:1 page ratio instead of 2:1, but I don't have any tool to deskew the pages.
I stumbled upon unpaper, another open source tool that seems perfect for what I want to do, but that tool is Linux only and it doesn't work on PDF files directly.
Any hint is appreciated.
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Pietro M.Pietro M.
marked as duplicate by random♦Jul 8 '12 at 3:23
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2 Answers
Have a look at deskew. It's a commandline tool. The download *zip seems to include binaries for Windows, MacOSX and Linux.
License is MPL (Mozilla) or LPGL (GNU), whatever you prefer.
The only drawback for you seems to be that it doesn't consume PDFs, only PNG and TIFF images (AFAICS). That means you'll have to set up a workflow of s.th. like:
I haven't tested it myself (yet), I just came across the website recently and bookmarked it.
Kurt PfeifleKurt Pfeifle9,70511 gold badge3737 silver badges5656 bronze badges
Oh, let me add another answer. I just remembered netpbm. Haven't used it in years, but I think I should take a fresh look..
netpbm is a very powerful toolkit for the commandline to manipulate of graphic images. It ships nearly 300 separate tools. It includes converters for about 100 graphics formats.
Adobe Pro Deskew
And it also has a commandline tool that can rotate images:
And it has another tool that tries to discover the angle of rotated images:
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pamtilt
returns a floating number of its guess of image rotation. So the automatic de-skewing of images should be within reach. A shell script could be written to do that. It would require different steps:- Convert PDF page to an netpbm-suitable image format with the help of Ghostscript.
- Use
pamtilt
to auto-discover the skew angle of the image. - Use
pnmrotate
to de-skew the image. - Re-convert the image to PDF.
If you provide me access to a small sample of your PDF files I could try and come up with a shell script to accomplish the feat.
(I'm wondering heavily that [netpbm] doesn't seent to have a tag here on the superuser+stackoverflow.)
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I recently received this email from a Michigan law firm:
Is there a straighten image tool for scanned images in Acrobat 11? My scanner is getting older and sometimes pulls documents through with a tilt.
Acrobat deskews (straightens) pages during the OCR process, but what if you do not want to OCR the document?
Acrobat can apply various image processing functions using the Optimize Scanned PDF function such as deskewing, background removal, descreening and more.
In this article, I’ll show you how to:
- Find and use Optimize Scanned PDF to deskew (straighten) pages in PDF documents
- Offer a pre-configured Acrobat XI Action which you can use as is to straighten PDF pages
Deskew Pdf Pages
Where is the Optimize Scanned PDF option?
Optimize Scanned PDF is found in the Document Processing panel which is hidden by default. To access this feature, you will need to show this panel.
Here’s how:
- Open the PDF document you wish to straighten
- Click the flyout menu at the top of the Tools panel:
- Select Document Processing from the list of available panels:
Deskew and Straighten PDF using Optimize Scanned PDF
- Open the PDF you wish to straighten in case it is not already open.
- Open the Document Processing panel and then click on Optimize Scanned PDF:
- To straighten the image without OCRing or changing compression, do the following:
A) Deselect “Apply Adaptive Compression”
B) Deselect “Make Searchable (Apply OCR)”
C) OPTIONAL: See below for Filter Section
The Filter section allows you to apply other image cleanup functions such as background removal, etc. You can experiment with these settings which can be helpful in some circumstances.
A Pre-built Deskewing Action
The steps above aren’t difficult, but if you have a number of documents to deskew or just want to save yourself a few clicks, you can try the Acrobat XI Action I’ve built for you.
Deskew Scanned PDF.sequ (2K)
The above link will take you to Acrobat.com. In the upper right hand corner of the window is a download button:
Save the file to a location you can find easily such as your desktop.
To import the Action
- Choose Tools > Action Wizard > Manage Actions.
- In the Manage Actions dialog box, click Import.
- In the Open dialog box, specify the name and location of the action file to import. Action files have a .sequ extension.
- Click Open.
To run the Action
- Choose Tools > Action Wizard > Deskew Scanned PDF
- Under Files To Be Processed, click Add Files to select the files that you want to run the action on. You can run the action on individual files or an entire folder of files
- When all the files you want to process are listed, click Start.