Creating Digital Line Drawings with GIMP

Today, I want to show you one of my favorite ways of creating digital line drawings from digital photos using GIMP.

GIMP stands for GNU Image Manipulation Program, and it’s a free, open source photo editor available for PC and Mac. If you’ve never used GIMP before, prepare for a fairly steep learning curve. Once you grasp the basics, however, GIMP is versatile, powerful, and an excellent alternative for Photoshop. It’s a great app if you prefer downloadable software.

I’ve already written about how easy it is to square up photos in GIMP. If you have problems getting good, square photos of your artwork, you’ll want to read that.

Now on to today’s subject.

Creating Digital Line Drawings with GIMP

Convert the Image to Gray Scale

Converting an image to grayscale removes all the color and turns the image into a black-and-white image. GIMP refers to this process as desaturation.

Select COLORS from the drop-down menu along the top of the GIMP window. Then choose DESATURATE and DESATURATE as shown below.

A dialog box will open that allows you to adjust the level of de-saturation. I usually click OK.

Here’s my sample image in full, glorious color.

And here is the fully de-saturated (converted to grayscale) image.

NOTE: Some photo editors automatically remove the color when you do an edge detection. Some do not, so you may or may not need to do this step.

Look for an Edge Detect or Find Edges Option

The next step is to reduce the image to edges.

In GIMP, you do that with the EDGE DETECT tool under the FILTERS drop down menu as shown here. I also use the DIFFERENCE OF GAUSSIANS option, which other photo editors may or may not have. If you don’t have that option, then choose the default. Most of the time, that option works best.

TIP: Set your photo editor up to show a preview of the changes you make, if possible. That way, you can see how the image is going to look before you apply the edge detect tool, and you can make adjustments if necessary.

This is how my image looked after finishing this step.

Adjust Brightness and Contrast

Next, adjust the brightness and contrast of the image. The goal is the best possible level of details with the least amount of distraction.

The BRIGHTNESS-CONTRAST settings in GIMP are under the COLORS drop down menu.

Another way to adjust the brightness and contrast is by selecting LEVELS (just below Brightness-Contrast in this illustration.)

There’s so much contrast in my sample image that the Brightness-Contrast setting didn’t help much, so I tried Levels instead.

There is still quite a bit of “noise” (unwanted details) in the background, but that’s easily enough ignored in the drawing process. The level of detail and value gradations in the subject is excellent.

Next….

Print the resulting image as is, or continue adjusting it until you have the level of detail you want.

You can also print this image and use it as a simplified reference to hand draw your own line drawing if you prefer.

Personally, I would print this image, then transfer only the details I thought absolutely necessary.

This process can be hit-and-miss sometimes. While default settings work most of the time, they may not be satisfactory with some photos. The problem is in the photos themselves. Lighting levels, clarity, and contrast all play a role. The better the photo is in each area, the better results you’ll get.

No matter what photo editor you use, you will have to make adjustments with some photos.

My sample required different settings in Brightness-Contrast, Levels, and in other places, than the last horse image I put through the process.

Creating Digital Line Drawings with a Photo Editor

This is a wonderful way to save time creating line drawings.

But no two photo editors are exactly alike, so explore your favorite photo editor and see what it can do.

After that, practice, practice, practice!

The only easier way to do this is to find someone else to do these conversions for you!