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Using GIMP, given a black text on a white area having some grayish smudges, how do I remove everything except the text?

for example this image, has gray outline around the text at places, I tried using the color tool with various tolerance but it always grabbed bits of the text. What is the proccess to be left with a sharper text? ( Redoing it in GIMP from scratch is easy, if one knows the font and size).

sample image

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up vote 2 down vote accepted

Don't know about GIMP, but in Photoshop you can just adjust the levels or curves so that the the grey smudges are hidden.

With levels you simply set the white point lower, at around 220 seems optimal.

enter image description here

Alternatively, you can adjust the RGB curve so that everything above 220 is output as 255 (white). This is similar to increasing the exposure to a photo. Then add a point at (105, 106) to anchor the lower tones to the baseline curve.

enter image description here

You can also play around with blurring the image slightly and then adjusting the curves/levels. By combining the blurred and unblurred version, you can get something like this:

enter image description here

Though personally I'd just recreate the image. It looks like it's done in Georgia bold or a similar font. It should take less time and get you much better results.

enter image description here

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Besides the method described by Lèse majesté (which, indeed, works just fine in GIMP), another useful noise removal tool to try, especially with JPEG compression noise like this, is Filters → Blur → Selective Gaussian Blur. Here's what I got after applying it to your example image with the default settings (radius 5.0, threshold 50):

Example image after selective Gaussian blur
(Usually you'll have to play with the settings a bit to find the optimal values for your image. I was just lucky that the defaults worked pretty well even without any tuning.)

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+1, thank you for the info, it is god to have alterantives! – Arjang Feb 27 '12 at 19:55

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