Converting a page photograph into black and white

The typescript of Ibn Abi Usaibia reached  me in the form of digital photos of the pages.  These were evidently taken under fluorescent light, since the images are huge, green, and weirdly coloured.  They’re so large, in fact, that they are hard to manipulate.

But I needed something a bit more normal.  So I was tinkering with the image and, quite by chance, got what I needed.  This tip may be of general use, where we have black text on white paper in funny-coloured photos, so I add it here.

  • Export the selected page from FR10 as an image.  Mine was a png, and came out as 32mb in size!  Here’s a snippet.  Note particularly the “see through” text to the left of the diagram.

  • Open with 3.5.10.  Trim to right size.
  • Adjustments | Black and White, to convert to greyscale.

  • Adjustments | Brightness contrast, to turn the background white.  So increase the brightness as far as you can without losing text.   The idea is to lose as much of the background as possible, and in particular any see-through text.  The text will be very grey.

  • Then you can also increase the contrast if you like.  Juggling the two should give a pale image.  Mine were brightness=100, contrast=20.
  • Then do Adjustments | Auto-level.  This will turn the pale grey text black again.  (If you didn’t get rid of enough background artefacts,  these will promptly appear as smudges, so you may have to go back a stage, and increase the contrast – that’s what disposes of a lot of them.)  The larger the image, the better the result when converted — this image is a little small, and the text ends up a bit fuzzy.

  • You can then do minor cleanup manually of dots etc.

As someone who is quite useless at image manipulation, I thought I would pass this on.

Ideally one would save the end product as black and white, but I haven’t worked out how to do that.

UPDATE: For some reason you can’t do it in Paint.Net.  But you can in the Windows accessory Paint, which comes free with Windows7.  Just do File | Properties, change the image to black and white and save.  The file size drops from 45k to 12k.  Here’s the sample:

Note that true 1-bit black and white doesn’t resize well — hence the jaggedness in the thumbnail above — but the full size version is fine.


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