Advise filters to improve text visibility on photo
I need filters to improve text visibility on photo, since it has some noise. Which filters (algorithms) do you know for this purpose?
Now, I use monochrome filter but it doesn't improve image quality. I need to filter can determine medium background of little area and make image monochrome depending on medium background.
For example almost all picture background is white and grey characters but some areas has darker color (grey) and black characters. I need to algorithm can understand that some area of image more darker and make level of black accepting lower.
For example, source image:
And processed photo (median, monochrome filters)
Unfortunately I'm not able to provide an accurate and fast answer using an image processing package in code, but I can provide some hints based on some really quick tests done in Photoshop(sorry, visual thinker, slow typist). Worst case scenario, you can run Photoshop filters from Matlab, but the filters are used should be available or not to difficult to implement since I've constraint myself to:
In simple terms, I recommend first getting read of the gradient dark to bright gradient: it will be easier to play with contrast/threshold on a more even image.
In Photoshop I applied curves (which other people wondered about implementing in code)
Not perfect, but it illustrates the idea of cancelling out a bit of that strong gradient.
On the resulting image I applied levels
Afterwards, a high pass:
You can use the high pass result and blend it (overlay) with the previous step which will emphasise the details
Asked in February 2016Viewed 2,782 timesVoted 14Answered 2 times