It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. We get PDF's from our professor to read for homework but they're often scanned documents, is there a way to adjust the contrast of the text to make it easier to read? This will not change the true contrast, but you can pick contrasting colors of your choice, or one of the defaults, as in the screenshot.
You could try Imagemagick - it's a graphics manipulation program that can read and write PDFs too. There are a few command line options that may help - for example: -normalize, -contrast and -contrast-stretch.
There are many filters, and one is for decreasing contrast. I saved it as a Microsoft Word file in Acrobat Reader. Then I opened the Word Document and adjusted the brightness and contrast of the image until it was readable. It makes for an expensive print, but it works. If you open it in Photoshop and resave as a PSD file you can or if you want to apply on all pages, do the following:.
I've run into this as well. I think it might be something in the creation, but I've not tracked it down yet. What I did was change the color of the text by going to edit menu, clicking on preferences and then the accessibility tab. You can customize the color for the document text.
It doesn't do anything for the images, but at least you can see the text on a dark background. See this post as well. It will affect the the whole system, but you can always change it back when you're done viewing the file. Essentially if you have a dark grey font on a light grey background a low contrast scan , then you tell it to "stretch" the dark grey to black and the light grey to white. I used this to create a legible black and white PDF from a scan that was originally black text on dark blue paper that scans as a very low contrast.
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Active 1 year ago. Viewed k times. Improve this question. Not only will this make the documents perfectly legible, but it will also shrink the file size dramatically.
Maybe you can turn this to your advantage and get some extra credit in return for rescanning or fixing the contrast on all the PDFs.
Related: softwarerecs. Add a comment. Active Oldest Votes. Improve this answer. KCotreau KCotreau I have tried this but it doesn't work. I think this works only for ebooks. My pdf is scanned text, so it's made of images. When do accessibility thing, the whole page goes white.
It doesn't recognize the text. I see. If it is a scanned image, I do not think there will be much you can do. I would mention it to the professor so he can consider adding contrast before he makes it a PDF. I set grey letters over black background using this method.
When I scroll down I get horizontal white stripes. Very annoying. There are many filters, and one is for decreasing contrast. What I did was change the color of the text by going to edit menu, clicking on preferences and then the accessibility tab.
You can customize the color for the document text. It doesn't do anything for the images, but at least you can see the text on a dark background. I saved it as a Microsoft Word file in Acrobat Reader. Then I opened the Word Document and adjusted the brightness and contrast of the image until it was readable.
It makes for an expensive print, but it works. If you open it in Photoshop and resave as a PSD file you can or if you want to apply on all pages, do the following:. I've run into this as well. I think it might be something in the creation, but I've not tracked it down yet. It will affect the the whole system, but you can always change it back when you're done viewing the file.
Essentially if you have a dark grey font on a light grey background a low contrast scan , then you tell it to 'stretch' the dark grey to black and the light grey to white. I used this to create a legible black and white PDF from a scan that was originally black text on dark blue paper that scans as a very low contrast.
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