dot be gone

Okay this is kinda bookish, so I figured I’d share.

When you scan an image from a book, it will contain DOTS, these are from the halftone printing method that uses same color dots of varying sizes to trick the eye. Anyway it’s the printing method used in books, newspaper etc.

But when you scan the image, you can’t really DO a whole lot with it, if you scan at a low res, you get a gray indistinct image, and if you scan at a high resolution you get a LOT of dots. Granted if you scan it high, and save it low, it will be clearer, but the odds are good you will still have a checkerboard pattern running through the image.

There is a that will help you remove repeating patterns, such as halftone dots or when a photo is printed on textured paper. It also works for Paint Shop Pro and CorelPhotopaint. After installation the Fourier Transform Plug-in appears as a filter. You run the filter against the image, then using the ‘red channel’ display you remove the frequencies that cause the repeating patter, then you run the inverse filter. It takes some practice, but the instructions are quite clear. The only thing they don’t tell you is that there is a size limit to the file you can work on, I found that 450dpi is ideal, but your mileage may vary. (If your red channel appears black your file is too big.) I try to do all my restorations at a high a resolution as I can, and then save down to a workable dpi. Things look much better that way.

I have used the filter on several images, with varying results, one with a lot of text, still came out poorly, but others like the one below came out spectacularly.

Download and install the filters, and next time you are scanning out of a book or newspaper, you can stomp out the dots.

Helen Gibson: Hazards of Helen 1915-1917

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