Producing a stippled image with Gimp

Here is a tutorial on how to use the Gimp to transform something like this:

into something like this:

You should be able to use the same process with any photo and then use the resulting stippled image as an underdrawing.

How Did the Old Masters Actually Paint?

I have put together an Amazon.com list on how did the Old Masters actually paint.

Open Source Methods To Transform A Photograph Into An Underdrawing

As promised, set forth below are the procedures for how to transform a photograph into an underdrawing using free, open source software.

No single software package will perform all of these steps, so you will have to download and install several different programs to perform each of these steps. For the purposes of clarity, I first will present several end results, then will tell you what steps to take and why. If any of these steps call for special software, I will link you to where you can get it.

Results:

A portrait:

Beginning with this photograph:

I achieved this result with open source tools:

As opposed to this result with Photoshop CS5:

A building:

Beginning with this photograph of the Parthenon:

I achieved this result with open source tools:

as opposed this this with Photoshop:

Why We Are Taking These Steps:

Basically, we are trying to make our photographs as sharp as possible. By so doing, we are bringing the greatest possible definition into them, we are highlighting the borders. These borders constitute the residual lines, which are all we are interested in for achieving an underdrawing.

Then we strip away as much of the rest of the photograph as we can. We get rid of the colors by desaturating. We radically simplify matters with the Threshold command. Absolutely all the steps we take, all the hoops we jump through, are nothing more than efforts to soup up the image, to obtain as much definition as possible, so as to give the Threshold command the maximum punch.

One of the best ways to soup up our image is with a technology known as tone mapping. While open source tone mapping tools exist; GIMP itself lacks tone mapping. Much of the complexity of the following discussion results from steps necessary to shuttle back and forth between GIMP and the tone mapping program.

There is nothing sacred or formulaic about these procedures. I am actually already experimenting with another possible method, and each photograph is unique. These steps are simply a means to an end which I have found to be generally satisfactory.

Finally, as part of my sharpening procedure, I have been using a high-pass filter. However, the tone mapping software I am now using also has something similar, called an unsharp mask. Apparently for this reason, applying the high pass filter with GIMP can be problematic. Sometimes - but not always - it fails to help or even hurts the result. So you just have to give it a try and, if you don't like the result, undo the filter, and then apply the Threshold command without it.

The Procedure:

1. I began with an underexposed RAW format photo of a pond that looked like this:
   
   
   
   
   
   
   
2. Convert to JPEG and correct image. Our tone mapping utility cannot process RAW files, so you have to convert it to JPEG. If your image already is JPEG, you can skip this step. Often, however, your photos will be in RAW format and cannot readily otherwise be converted.
   
   I imported this image into UFRaw, an open source raw correction utility comparable to Adobe's Camera Raw.
   
   This allowed me to boost the images exposure, which was helpful.
   
   More importantly, it enabled me to convert the image to JPEG, which is vital. UFRaw can be installed as a GIMP plug-in. On the lower right corner of the program is a button marked with a GIMP icon. Click that to load your RAW file into GIMP. Then, in GIMP, click "File/Save As..." to save the image in JPEG format. I obtained this result:
   
   
   
   
   To download install UFRaw, click heer. For its User Guide, click here.
   
3. Apply tone mapping. I imported this JPEG into LDR Tonemapping.
   
   I have found this program to be simpler and more reliable than Luminance / qtpfsgui ( which you nevertheless can still use so long as, in the previous step, you convert your image to TIFF rather than to JPEG. ).
   
   After trying to make the image as sharp as possible, I obtained the following:
   
   
   
   
   
   To download LDR Tonemapping, click here
   
   
4. Import into GIMP and desaturate.. I re-imported the image back into GIMP and converted to greyscale by clicking "Colors/Desaturate..." for the following:
   
   
   
   
   
5. Run the high pass filter. While GIMP itself lacks a high pass filter, you can download and install a plugin that will do that. After installing, you can click "Filters/Generic/High Pass Filter" to get it.
   
   Because this filter has no preview, you are shooting in the dark while applying settings. Shove the sliders back and forth to obtain various settings, which you can undo with "Edit/Undo High Pass Filter." You are attempting to make the image look more like an etching. After several attempts, choose the settings that come closest to that.
   
   This is what I got:
   
   
   
   
   
6. Apply the Threshold CommandAfter applying the "Colors/Threshold..." command I obtained this final result:
   
   
   

Concluding Comments

As I noted, the high pass filter can be problematic. Omitting it entirely yielded this:

Experiment with these tools. Here are two other results I have obtained:

The Fall of Icarus

Pieter Bruegel's Landscape with the Fall of Icarus provides us with a clue for how to go about obtaining images which, after we have converted them into underdrawings, we can thereupon paint.

We want to avoid composed, contrived settings. Sharp, well composed and focused photos are just fine as is. Why transform those into paintings? But setting up a good photo is a left brain enterprise. We are painters and - while we do use cameras to capture our image - our purpose is to draw upon if not necessarily to draw on the right side of the brain. To uncover the out of focus image that we glimpse out of the corner of our eye.

So how do we do this with a camera?

Landscape with the Fall of Icarus portrays a fine Flemish landscape:

But the real subject is Icarus' fall,  tucked away in the lower right:

We go around with the left side of our brains seeking fine Flemish landscapes to photograph. Only later do we notice that "Hey! I've got a shot of Icarus falling here." And that's what we want to paint.

For example, here we have an underexposed, poorly arranged, tilted photograph:

Certainly this is an unpromising photo. But this young lady is its Icarus:

And here is her photo converted to an underdrawing:

This means, generally speaking, you want a camera with a wide angle lens, a deep depth of field, and shutter speed fast enough to prevent blurring. This will enable you to capture as much imagery as possible. You will decide - or, rather, you will discover - what actually to display later. As for the artistic effects and visual impacts - that is what painting is for.

An Open Source Alternative

Following Meg's suggestion, I have explored open source alternative approaches to converting a photograph into an underdrawing.

In addition to the Gimp, I used an open source HDR prgram, Qtpfsgui.

These are simply the results. I will publish detailed procedures later.

Open Source:

Photoshop:

After being imported into Painter and further adjusted, here's how they compare

Open Source:

Photoshop:

Remember, the particular differences between the two photos here probably suggest nothing about the inherent properties of the two approaches. Do not conclude that the Open Source would always be more robust or the Photoshop more refined. Both programs could be adjusted to produce differing results; and this is the first time I have ever attempted to transform via the Open Source approach. Rather, focus on the similarities between the and the feasibility of the Open Source option. Here's another, lighter Open Source version obtained by adjusting a few controls:

How To Transform A Photograph Into An Underdrawing

Our first step will be to use Adobe Camera Raw, then Photoshop, then Corel Painter to transform a photograph into an underdrawing.

Here are the steps we take:

1. Let us begin with this photograph. It is a digital photograph in Camera RAW format.
   
   
   
   
   This is a dark photograph the color of which might suggest Rembrandt while its atmosphere might suggest Reubens. But its low contrast inhibits our efforts to transform it into a drawing.
   
2. So we import it into Adobe Camera Raw, where we increase its fill light and its contrast to achieve the following picture:
   
   
   This transformation brings out many previously obscured details.
   
3. Now we import this photograph into Photoshop CS5, where we use the new HDR Toning to convert to greyscale. Click "Image/Adjustments/HDR Toning..." to open the HDR Toning dialog box. Reduce the saturation to its minimum level while raising the detail. Consider other adjustments that would make the picture sharper and punchier. Get the following result:
   
   
   Photoshop has other methods to transform color photos to black and white. You can experiment with those, but so far I have found them less sharp. And sharpness is good when you want to transform a photograph into a drawing.
   
4. Now we run our photograph through the High Pass filter to make it resemble an etching. Click "Filter/Other/High Pass..." to get the following result:
   
   
5. Then we add a Threshold adjustment layer to transform it into a black and white outline. Goto the layers panel, click on the adjustment layers icon and select "Threshold..." for the following result:
   
   
   
   Save the file in PNG, GIF, or JPEG format and exit Photoshop.
   
6. Now goto Corel Painter to color this drawing with burnt umber. Painter has an "Artists Oils" color set. Using this color set, you can manipulate most of the colors with which we are familiar when using physical media such as oils, acrylics, or water color: cadmium blue, permanent alizarin crimson, raw sienna, and so forth. It is a swatch panel preset with those colors which you already know. Burnt umber is one of them. To load, open your color panel with "Window/Color Panels/Color Sets." Then click on the triangle on the panel's upper right hand corner to get "Open Color Set..." A dialog box will appear warning you that the new color set will overwrite your old one. Ignore this warning and click "Load." Then select "Artists Oils Colors.colors" from your available options.
   
7. Then load burnt umber as your primary color. It is the swatch on the third row from the bottom and the third column from the left.
   
8. Add a new layer above your canvas. Open the Layers panel by clicking "Window/Layers." Then click the "New Layer" icon.
   
9. Fill this new layer with burnt umber. Click the layer to be sure it has been selected. Click "Edit/Fill.." to launch the Fill dialog box. Set it to fill with current color and set the opacity to 50 percent. You get the following:
   
   
10. This is too dark but can be corrected with a blending mode. Goto your layers panel and change the blending mode from "Default" to "Color." You get the following, which is our final result:
    
    
    Or rather, we have achieved an underdrawing upon which we can do some real painting.
    

This technique is not limited to portraits. For example, similar steps transformed this photograph of the lighthouse in Chania harbor, Crete:

into this underdrawing:

Our Basic Approach

The purpose of this blog is to take David Hockney's thesis that Old Masters achieved the photographic qualities of their paintings by projecting camera obscura techniques to project the image of their subject onto a painting's surface and to use this thesis as a basis for us to compose our own paintings.

Hockney sets forth his thesis in Secret Knowledge (New and Expanded Edition): Rediscovering the Lost Techniques of the Old Masters. According to the Amazon.com review:

British painter David Hockney, well known for his cool and lovely paintings of California pools, has taken on the new role of detective. For two years Hockney seriously investigated the painting techniques of the old masters, and like any admirable sleuth, compiled substantial evidence to support his revolutionary theory. Secret Knowledge is the fruit of this labor, an exhaustive treatise in pictures revealing clues that some of the world's most famous painters, Ingres, Velázquez, Caravaggio (just to mention a few) utilized optics and lenses in creating their masterpieces. Hockney's fascination with the subject is contagious, and the book feels almost like a game with each analysis a "How'd they do that?" instead of a whodunit. While some may find the technical revelation a disappointment in terms of the idea of genius, Hockney is quick to point out that the use of optics does not diminish the immensity of artistic achievement. He reminds the reader that a tool is just a tool, and it is still the artist's hand and creative vision that produce a work of art. (296 pages, 460 illustrations, 402 in color.) --J.P. Cohen --This text refers to an out of print or unavailable edition of this title.

Nowadays, we don't have to use camera obscura to achieve the sort of techniques that Hockney ascribes to the Old Masters. Rather, by using digital photographs, Adobe Photoshop, and Corel Painter, we can follow essentially the same steps.

In this blog, we shall adapt Old Master techniques into equivalent Photoshop or Painter techniques, thereby practicing what Hockney preaches.

Is Hockney historically accurate? I don't know and - frankly - who cares? What matters is that by using his thesis as a sounding board and combining it with available software, we ourselves can achieve interesting and worthwhile effects.

So let's go.