I have pdfs of my homework assignment written in pencil. I was supposed to write it in pen. I am looking for a software that changes the colour of my handwriting to blue/black colour. Please help, Thanks in advance!

Edit: I wrote my homework assignment in a ruled notebook, then I scanned the images, and

something like this, for example,

Mohandas K. Gandhi, letter in indelible pencil, South Africa 1909.jpg

Basically, a pencil handwriting can be erased by eraser. It is light.

I found a very useful free PDF colour inverter online: invert-pdf.club (Perfect for printing dark PDFs.)

I found another website: online2pdf.com/pdf-change-color-to-black-and-white I can change the pdf color to grayscale or monochrome.

BUt i am still not able to find a tool that changes color blue/black

1 Answer 1


I'd suggest to use GNU GIMP. You can 1) change to grey scale (Image > Mode, it is second menu item) 2) change contrast and brightness first so that the background is more white (under Color menu) 3) change back to color mode (Image > MODE) 4) adjust blue color balance there (under Color menu)

Though I would suggest first to put the document under a glass and improve the lighting in the room. If you don't have glass you can use something simple transparent like a refridgerator shelf. Even if it is missing, moving the document to a better lit area would help.

Tried it and got this:

enter image description here

If I skip the contrast editing and just do step 4, then here is what it looks like:

enter image description here

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