From Photo to Line Drawing....Without Leaving RawTherapee .

The jpg of the girl in the fur outfit has a moderate resolution: 804 by 629 pixels. While working with high resolution Raw files will generate interesting images, if you are after a line drawing medium resolution jpgs works best. That way you can view your image at 100 percent. You will be creating what would be called artifacts in a normal workflow and it is easy to go a bit too far with the sliders.

Step one

Start by upping the exposure compensation. For a realistic line drawing keep detail in at least one of the color channel in areas such as the girl's face. In other areas that will be paper white in the line drawing such as the girl's skirt you can push all channel to 100 percent,

Step two

Tone map the jpg to create edges without turning shadows into blotchy artifacts in area such as the girl's face.

Step three

If you like your original colors  this and the next step are optional. Using the three color temperature sliders produces a wide range of color shifts ranging from a total color cast to a blue tinting of the edges created in step two.

Step four

Again this step is optional.  The channel mixer switches the colors towards green.

Now another big reason for using roughly 800 pixel resolution jpgs, The bottom sliders in the contrast-by-detail tool creates hard edges. With higher resolution images the effect is nowhere as strong.

My original final image.

A water color perhaps rather than a line drawing but still an attractive image. Because of the interactions between the tools pushing beyond this didn't work out. But after I slept on the problem when I woke up I realize that if I did a second pass stating with my painterly jpg I wouldn't be fighting any interactions.

Repeating step one and two--more exposure, more tone mapping, and then setting the saturation down to -100 created this  line drawing.

Edit

Variations on a theme.

Toss in the black and white tool channel mixer and you have a ton of manipulations to play with. Here are two examples

These images were created with RawTherapee build 4.2.77. It is open source and forever free and can be downloaded at  http://rawtherapee.com/downloads

Matching skin tones for a Kodak Moment

Every now and then I've seen posts asking how to duplicate the look of a favorite film. I've played around with the idea myself with some occasional success.  Perhaps my most successful attempt was back in ancient years--my Photoshop days--where I exhibited an image that duplicated the National Geographic look of the 1920s and 1930s.  A bit of a hassle as I remember where it took several tries before what came off the print shop's Fuji Frontier machine look like what was printed in the magazine. A learning experience and my first attempt at color management.

Now we have RT with CIECAM . The tutorial is about duplicating what the 1950s ads in National Geographic called a Kodak Moment.

Why am I working on a jpg, Raw's poor and looked down upon cousin?  Because there are a lot of  jpgs out in the world, including a several year collection backed up on my computer. Call this a gentle reminder that RT is also one of the finest jpg editor around.

This image is from Charlotte's kindergarten dance recital. It was taken flashless and handheld with a point and shoot back when ISO400 was the ultimate in digital sensitivity. So it is nowhere near as crisp and noise free as an image I would take today. But it has family significance.

When Charlotte moved on to first grade she dropped out of dance because it was no longer just fun and play and had became real work learning real dance moves. But now that she is an almost seventh grader going on high school junior she has changed her mind. Her summer vacation will be afternoons of private dance lessons followed by several weeks of 8 to 5 dance camp. With weekly  recitals that I will immortalize in pixels and  then combine with the highlight of this recital to make a photobook or calendar for mom and the grandmas. Early Xmas shopping on steroids

Pass one was standard ISO high corrections to.brightened and cleaned up the image.

Pass two added an CIECAM tone curve to lighten the girls faces without washing out their costumes. Of the two curve choices the Lightness curve was stronger than the Brightness curve

Pass three was to use the  'All' algorithm to fine tune the facial tones of the image to match those on the cover of the Kodak pamphlet.  This wasn't done with any great science; just moving sliders around until the tone match looked reasonably close. Nor was this a challenging image since I was only working with one critical tone. But it does demonstrate a workflow.

 Converted with RawTherapee 4.0.12.165  which  can be found at http://rawtherapee.com/downloads