Sharpening text in a jpg image

[PAL Thai]

   
Hi!  I'm quite new to GIMP and would like to make use of its capabilities as follows:
I have a .jpg image of an outdoor sign  that when zoomed to 400% shows the white text of the sign quite blurred.  I am hoping to find the proper way to sharpen and whiten just the white text and leave everything else on the image as it is, i.e. slightly blurred.  I have attached the file in question so you can see for yourself what I am talking about.  The border and empty space surrounding the image must remain as seen so as to have the correct size for posting to a Yahoo! Page. Many thanks to those members who may help me out.

[rich2005]

Lots of jpeg artefacts. The image maybe exported at low quality / scaled up from a tiny image.

Try:

1. Duplicate the image layer Layer -> Duplicate Layer and in the new top layer use the Threshold tool Colors -> Treshold Move the center slider a little to the left to make white areas whiter.

2. Paint out in black all of the background leaving the text.

screenshots https://i.imgur.com/vu0xF3F.jpg

3. Apply a small (values = 3) Gaussian Blur Filters -> Blur -> Gaussian Blur

4. In the layers dialogue change the mode of the top layer to Screen

5. Exporting as a new jpeg? Untick all the exif stuff. Do you need that comment? Otherwise default values give a file size much the same as the original.

screenshots https://i.imgur.com/ujAUYSo.jpg

edit: I wish I could give some simple way to improve that overall. Guessing at much of the jpeg artefacts actually come from over-sharpening. A partial reconstruction, scale the image up 400% then clean up, scale back down to original size, new borders to finish. Not a quick process. Gets this.

   

[PAL Thai]

(01-15-2019, 09:01 AM)rich2005 Wrote: Lots of jpeg artefacts. The image maybe exported at low quality / scaled up from a tiny image.

Try:

1. Duplicate the image layer Layer -> Duplicate Layer and in the new top layer use the Threshold tool Colors -> Treshold Move the center slider a little to the left to make white areas whiter.

2. Paint out in black all of the background leaving the text.

screenshots https://i.imgur.com/vu0xF3F.jpg

3. Apply a small (values = 3) Gaussian Blur Filters -> Blur -> Gaussian Blur

4. In the layers dialogue change the mode of the top layer to Screen

5. Exporting as a new jpeg? Untick all the exif stuff. Do you need that comment? Otherwise default values give a file size much the same as the original.

screenshots https://i.imgur.com/ujAUYSo.jpg

edit: I wish I could give some simple way to improve that overall. Guessing at much of the jpeg artefacts actually come from over-sharpening. A partial reconstruction, scale the image up 400% then clean up, scale back down to original size, new borders to finish. Not a quick process. Gets this.

---

Many thanks for the suggestions and a peek at the finished product. I will print out your post and use its contents as I try my hand at sharpening the white text of the jpg in question.

I'll keep my fingers crossed as I move through the steps since I'm quite new to GIMP. But the last picturein your post really does sharpen the white text and makes it very legible indeed.