Make Text from Image More Readable

Question

Is there a particular agorithm to maximize visibility of text from image below?

I am not very familiar with Adobe products, so are there suggested filters I could utilize?

Thank you!

Answer 1

You can recover 'gross' detail using curves, as mentioned in Hueco's post. You can additionally desaturate, leaving an essentially black & white image.

This will be somewhat more legible…

however, fine detail cannot be recovered because it has already been lost in the jpg compression, leading to these ghosting artefacts around the edges of each letter…

This may be recoverable using a dedicated scan/reader app, though I've tried Readiris Pro & it can't read this page, quality is too low.

Answer 2

Part of the problem is the original image. Read up on copy stand photography.

Things that help create a better image:

1. Get a chunk of heavy glass. You want plate glass, not float glass. Plate glass is ground flat. Float glass has ripples. Ideal is a piece about 3/4" thick. This has to be larger than the pages. You can use glass as thin as 1/4" but you may need additional pressure to hold the book flat.

2. Create a support system so that you can make the page at right angles to the camera axis.

3. Illuminate the page with two lights about 45 degrees offaxis. This eliminates reflections off the glass.

4. Suspend a dark cloth as a background behind/above the camera so you don't get reflections off the ceiling/wall behind you in the glass.

5. Shoot at minimum ISO to reduce noise.

6. Turn off image stabilization.

7. Work from a tripod.

8. Use your sharpest f/stop. (Usually f/8)

9. Use a remote trigger, or shoot as a set of timed exposures. (E.g. Once you find you can remove the glass, flip the page, replace the glass in 12 seconds, set the timer to take a shot every 15 seconds.)

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Do your initial setup using a sheet of lightly ruled graph paper as a target. This allows you to check that you are square to the glass. (Each edge of the image will have equal numbers of graph squares.) The lightly ruled aspect will allow you to adjust exposure and contrast to get sharp edges.

I have a tamron 90 mm f/2.8 macro lens I use for this sort of work. 90mm allows me reasonable working distance from the page.

You will need to do some tests to find the right exposure.

Answer 3

I highly recommend you use instead a document scanning app like Genius Scan. The algorithm to straighten, enhance black and white, and save to pdf is built into those programs and it it far more useful than dealing with jpgs.

But, if you must, you can use any editor to modify the “curves” of the image:

The normal curve line is on the 45 degree line. Note the histogram and how the left curve was simply drug over to the left side of the histogram. This darkens everything, including the text, so that it stands out more from the page.

Answer 4

The problem of using simple color modifications on the raw document is that they apply equally to text and to background, so you are often limited in what you can do. My favorite technique with Gimp is to:

1. Use the "Wavelet-decompose" filter to decompose the image in its frequency components
2. Bucket-fill the bottom layer ("Residual", the very low frequency components) with white
3. You can duplicate the top levels (high-level detail) to increase sharpness
4. Use Curves to restore the black and white points and add some contrast on the result

Without Wavelet decompose, there is an older technique (grain-extract a blurred copy of the image) to remove background variations, that I can add if interested.