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Is there any way to change the speckly black background of this screen photo to solid black?

enter image description here

This is a photo of a rectangular selection of a black screen that appears when a computer is booting. To the eye this screen has only three colors. OK is bright green, the other text is white and the background is black, however in this screen photo the background is mottled black and gray instead of solid black. In order to see the speckly background more clearly click anywhere on the image with the mouse.

I want to change the speckly black and gray background to solid black without losing image resolution. I tried using the Colors -> Threshold option in GIMP, but it results in losing too much resolution.

I have several different image editors, among them Photoshop, GIMP and Darktable, so the choice of software is not important to me as long as I can obtain a higher quality image. A general solution that works with other colors is not important to me either. If black, white or green is off color I can correct it myself, so for the purpose of answering this question you can assume that the image has already been color corrected to be similar to the image in this question.

I've already tried OCR, but it doesn't work for this situation because OCR introduces small errors into the boot screens which I'm not always able to catch. The boot screens can't have any errors because their purpose is to troubleshoot boot problems, and small errors in the boot screen can result in big problems with booting the computer, so all of the text has to be exactly the same as in the original images.

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    You would get better quality if you figure out what the font is and rewrite the text. It would help to know what boot screen that is from, but there might be something at least sorta close here: int10h.org/oldschool-pc-fonts/fontlist — This isn't exact, but definitely similar: Link to preview (The actual preview is below the green "DO IT" button.) – Joonas Dec 19 '18 at 9:58
  • @Joonas Thanks for commenting. That font looks right, but I can't retype everything on the boot screen because the full boot screen photo is a solid wall of text, so it's faster to just edit it. – karel Dec 19 '18 at 10:11
  • You seem to have your mind set that in this case fast with poor quality defeats slow with better quality, buuuut I pushed your image through www.onlineocr.net and it actually came out alright: pastebin link. Just a few hiccups here and there. – Joonas Dec 19 '18 at 10:24
  • My goal is that I have hundreds of images that need to be improved, and my objective is to get decent readabilty for the casual reader. I've already tried it with OCR. OCR takes me about one hour per image and more importantly OCR would inevitably introduce small errors into the results that I wouldn't be able to catch, and these errors would be fatal to the purpose of the boot screens which is to troubleshoot boot problems. I need an exact image that is of sufficiently good quality to be easily readable. – karel Dec 19 '18 at 11:08
  • Yea that sounds about right... – Joonas Dec 19 '18 at 11:29
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In Gimp:

Just use the Brightness/Contrast tool to increase contrast (up to 66 in the image below):

enter image description here

  • This does exactly what I wanted. Contrast of 50 worked for me. – karel Dec 19 '18 at 9:47
  • I have been improving a batch of boot screen images and I found out one more thing. If the resolution of the image is low to begin with, increasing the contrast makes the resolution noticeably lower. For this reason I recommend making a backup copy of each image before editing it. That way it is possible to compare the two images and select the better one. If the image has a normal resolution, then increasing the contrast should improve it. – karel Dec 19 '18 at 15:33

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