Deskew Scanned Pdf
Introduction
The most recent version of this scrip is locatedhere.
Today, Red Software announces a new 'Deskew' tool for its free PDF editor, PDFescape. As many people know, scanned documents don't always come out as perfect PDFs. One of the most common problems, a skewed page. We're proud to announce that PDFescape now provides a free solution to that problem! If you just drag a already scanned PDF file into PDFPen Pro you can still Deskew it if you access the “Deskew and Adjust Image” command in the Edit menu: So, why not just use PDFPen Pro you ask? Because PDFPen Pro is expensive. There is no better App out there if you do much work with PDF files. A-PDF Deskew provides a quick way to correct the skew scanned image in Acrobat PDF documents directly. It detects tilt images and straightens them automatically. Acrobat can apply various image processing functions using the Optimize Scanned PDF function such as deskewing, background removal, descreening and more. PDFill PDF Deskew provides a quick way to correct the skew in the scanned images from Acrobat PDF documents. In this process, the original PDF page is inserted into a new blank PDF page. So, you can change the new page size. You can rotate, transform, scale, or crop the PDF page just like the way as you work on an image.
One nice way to save old notes is to scan them to a PDF. However, not all scanners makethe notes correctly orientated along with also taking up a lot of space. There areseveral methods to make notes look better likeunpaper orpdfsandwich. It is also possible to enhancenotes such as using mzucker’s noteshrinkapproach or use ImageMagick to dothe conversion such as lelandbatey’s whiteboardcleaner, but this last method can be quiteslow on single images.
This solution mostly focuses on black and white notes, and can be changed to use color. Itcan shrink a pdf to about 20% of its size depending on how many lines there are on thepage. It can also deskew notes that unpaper can not deskew, and can be modified veryeasily.
Examples
The image on the left is the original image (JPG 210.4 KiB, PNG 680.9 KiB) and the imageon the right is the deskewed image (PNG 171.9 KiB). The image to PDF method (img2pdf) onlyadds an additional 500 to 700 Bytes to the overall file size, and as such does not reducethe image quality (unlike ImageMagick).
Another example is when using the dark border removal, which happens when the backgroundof the scanner uses black instead of white.
Like the first example, the image on the left is the original image (JPG 354.5 KiB, PNG1.6 MiB) and the image on the right is the converted image (PNG 44.0 KiB).
Running deskew.sh
This script uses bash, mktemp (from coreutils), pdfinfo and pdftoppm (from poppler-utils),convert (from imagemagick), img2pdf, gs (from ghostscript), and exiftool (fromlibimage-exiftool-perl).
Deskew Scanned Pdf Files
This tool also comes with several command line switches, along with defaults used when theswitch is not present.
- -b is the amount of offset inpixels to change. Thedefault is 5.
- -d is the dpi that will be used on the PDFs. The default is 325.
- -h is the help menu.
- -p is the PDF image file format used foreach image. The default is pgm (gray).
- -o signifies the output file. By default, the original file has _skew added to the endof the file and the new file named after the original file.
- -r creates a 1 pixel black border, and then changes any black pixels linked to thatborder to white.