Program to enhance or increase the contrast of a PDF scan?

I have a PDF scan that looks quite pale, and the signature and date are barely legible. Is there a program that can enhance the font or increase the contrast?

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Commodore64
4 months ago

You can do this with a graphic editing program. GIMP can open PDF and then you can set contrast etc.

You can even click in the picture what white should be and what black. Then he pulls the values so that the gray bead is actually white from paper and the letters black.

The gamma correction is also suitable for making the gray loop white and the letters are full black. Here you can also easily see how far you can go without the fringes.

Then there would be the “Scantailor”. Automates the processing of scanned documents. It is possible to separate book pages, correct slants and distortions (photographed book), save data only 1-bit and images with correspondingly more color depth and much more. Documents not only look much better, but also become much smaller in file size. I’m not 100% sure now, but it would have to open PDF. I convert them into individual images or scan them as individual images.

GammaFoto
4 months ago

If you scan an image or document, then you get a normal pixel image at the end of it, so nothing other than a JPG. And this is also only stored as a JPG in your PDF. The PDF is basically only the “package” for a JPG, a so-called container file

This is basically what every program should be able to open and edit the images, so besides of course Photoshop, this also goes with free programs like GIMP and usually this should also be possible with online tools.

gufrastella
4 months ago

Hello, Cocactus!

With the PDF24 tool, you can convert and store a PDF into an image that can be improved with an image processing program: lower the gamma value and increase the contrast. Then you can print the image again as PDF with PDF24.

LG

gufrastella

GammaFoto
4 months ago
Reply to  gufrastella

funfact: the scanned is of course a picture, a pure JPG file within a PDF container

gufrastella
4 months ago
Reply to  GammaFoto

Yes, that came out in the question text that it is a scan and thus an image file that is contained in the PDF file 😊. I chose the wording “to convert a picture” as the function of the tool is called. Extracting the image still remains necessary, no matter what program you want to do.

Kwalliteht
4 months ago

Do not scan as PDF, but as TIFF. Customize contrast with any graphics program and then save as PDF.