Removing the blue-line markings from your inks without Photoshop

9 Nov

On a Mac, if you have Photoshop, removing the underdrawing in blue lead pencil is easy. Just convert into CMYK and clear the C, M and Y channels, so you’re left with a black channel. However, in a program like Pixelmator there is no such option (yet). Apart from “copping out” and using GIMP, how do you remove that blue pencil without CMYK separation?

Well, I found a solution (workaround) using Sheashore. Seashore is a freeware Cocoa-based application that uses the GIMP engine. You can read and write XCF files with it (the native GIMP file format). It has a handy feature Pixelmator lacks, namely a layer mode called “Divide”.

Step 1. Scan the drawing

Here is the original blue-line and ink drawing I scanned.

Agent Smith, phase 1

Step 2. Remove the blue color

Opened in Seashore, I picked the color of the blue lead pencil. Next, I added a layer on top of the scanned image layer, and filled it with the picked color. The layer mode was changed into “Divide”, which gave the result you see below.

If it doesn’t remove the blue pencil markings, you probably picked the wrong color. While in the layer containing the scanned image, look for instances on the screen where the original blue is still visible, select that color, use it to fill the layer on top, and see if it removes (most of) the blues. If it does, then go on to the next step. You can remove any remainders of the blue color during retouch.

Agent Smith, phase 2

Step 3. Clean up and finishing touches

I exported the file from within Seashore as a TIFF file, which I imported into Pixelmator for clean up. The colors were desaturated, the image optimized and small retouches were made. Next the blacks were filled, which gave this result.

Agent Smith, phase 3

Why, Mr. Anderson, why, why, why?

You might ask, why not use GIMP if you can’t afford Photoshop (Pixelmator is a paid application, but much more affordable)? Well, because I want to use an application that adds auto-save capabilities to my applications. Such a program is ForeverSave Lite. If you have ever lost an image file due to a crash, you appreciate such little gems.

However, it only seems to work on Cocoa-based applications, and GIMP isn’t that (it is a X11-based application). Even Art Rage 2 (which I love) isn’t a Cocoa-based application (it can’t be, because it is written in C++, as far as I know, to enable simultaneous development of a Windows and Mac version, so it has to be Carbon-based). ForeverSave Lite seems to need the Cocoa framework to access the save function of an application.

For efficiency reasons, your original scan, the color-separated version and the final version should be separate files anyway. So, if your workflow enforces that, you’ll never be tempted to take shortcuts and overwrite your originals. I’ve done that, and regretted it when I couldn’t go back when I needed to.

That is all.

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