How to convert a picture into black lines and a transparent background?

Question

I've looked at a couple of previous questions, but I haven't been able to apply it to my question.

I'm trying to extract the black from this picture (so I can turn it into a vector later in Illustrator):

One answer to this previous question suggested fiddling with the input levels, but mine don't look as nice as the ones they show and I can't find a setting where white is totally white and black is totally black.

When I add an adjustment layer converting it to black and white and I try to place it into Illustrator, I get this:

I've also tried following this answer's suggestion and do filter | stylize | find edges and I'm getting close, but I don't have optimal results yet:

Answer 1

For your image I would use Channels.

Go into your channels and notice the red one has the best contrast. Duplicate that channel and then use the Curves to adjust it. At the bottom of the Curves panel you can eyedrop the black point to your text and the white point to the background. Maybe tweak it a little. You get pretty close already. Might have to do the "Just Right" part on its own since its a bit lighter but in no time you should be real close.

Then just use that as a Mask on your original:

I'd clean up the little bit that's still rough on the edge which should take two seconds and like I said probably do the "Just Right" again with the same technique but making sure its pure black if that's what you want.

Answer 2

what I did is : used black&white fill and then use level(Ctrl+L)and make it full white background, see screenshot-1

Then I merge all three layer which you can see on layer panel in first screenshot using (Ctrl+E), and used magic wand tool to select the white background and ka-boom.. press DEL button.. :) Got transparent image

Answer 3

Photos of papers are almost always unevenly lighted. This makes using Levels very hard because it has to be a compromise between noise, leftover shading and losing lines. However, there's an easy solution.

Like others have already suggested, first you need to pick a color channel with the least noise. In your case, I picked green. Copy it into a new document.

Now follow these steps (numbers are specific to your image, others will need to adjust as needed):

1. Duplicate layer — the new "paper" layer
2. Median (2 pixels) — removes small noise to avoid problems on the next step
3. Maximum (10 pixels) — removes lines, adjust radius until you see almost all lines disappear
4. Spot Healing Brush if there're some dark spots left
5. Gaussian Blur (10 pixels) — to clean up circles/squares from Maximum, radius should be equal or bigger
6. Invert colors, set layer blending mode to Liner Dodge (Add) — subtracts the "paper" level from the source
7. Levels (50 to 235) — removes noise and increases contrast

Some additional dark magic with Content-Aware Fill may be required if lines are very light and grey, but usually this is enough already.

Result

Notice how all shading was removed, there's no noise and no lines became thinner. The image is ready to be traced in Adobe Illustrator.

Answer 4

still one more:

1. remove smooth luminosity variations (=low spatial frequencies) by applying high pass filtering:

2. Increase contrast to get black and white. Use curves. Let there be a non-vertical transition zone, do not apply steep tresholding because it generates harsh edges:

There's still some color left. Desaturate to remove it, if needed.

Just to show what you can expect there's a comparison:

The grey version is the fixed photo, it's only made partially transparent to make it grey. It's for better visibility of the red version. The red curve is the tracing result moved a little aside and with no fill, but with a thin red stroke.