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− | One of the perennial problems that we have come across in a variety of contexts, including [http://www.evilmadscientist.com/2012/cnc-halftones-with-ascii-art/ CNC artwork] and producing artwork for the [http:// | + | One of the perennial problems that we have come across in a variety of contexts, including [http://www.evilmadscientist.com/2012/cnc-halftones-with-ascii-art/ CNC artwork] and producing artwork for the [http://evilmadscience.com/productsmenu/tinykitlist/171-egg-bot Egg-Bot], is the difficulty of creating good-quality toolpaths– i.e., vector artwork representing halftones –when starting from image files. One of the finest solutions that we’ve ever come across is [http://mrl.nyu.edu/~ajsecord/stipples.html Adrian Secord's algorithm], which uses an iterative relaxation process to optimize a weighted [http://en.wikipedia.org/wiki/Voronoi_diagram Voronoi diagram], mathematically producing a set of points (stipples) that can closely approach the appearance of a traditional stipple drawing. |
Another important technique is [[TSP art]], where the image is represented by a single continuous path. You can generate a path like this by connecting all of the dots in a stipple diagram. Designing a route that visits each dot exactly once (and minimizing the distance travelled) is an example of the famous [http://en.wikipedia.org/wiki/Travelling_salesman_problem Travelling Salesman Problem] (or just “TSP”), and an optimal TSP path can give a surprisingly good grayscale representation of an image. From the standpoint of toolpaths (for the Egg-bot and most other CNC machines), a TSP path is even nicer than stipples, because little or no time is spent raising and lowering the tool. | Another important technique is [[TSP art]], where the image is represented by a single continuous path. You can generate a path like this by connecting all of the dots in a stipple diagram. Designing a route that visits each dot exactly once (and minimizing the distance travelled) is an example of the famous [http://en.wikipedia.org/wiki/Travelling_salesman_problem Travelling Salesman Problem] (or just “TSP”), and an optimal TSP path can give a surprisingly good grayscale representation of an image. From the standpoint of toolpaths (for the Egg-bot and most other CNC machines), a TSP path is even nicer than stipples, because little or no time is spent raising and lowering the tool. | ||
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StippleGen is easy-to-use software that can generate TSP and stipple drawings from input images. It saves its files as editable, Eggbot-ready Inkscape SVG files, which can in turn be opened by other vector graphics programs, or re-saved as PDF files for use in other contexts. It can also generate a TSP path from the stippled image, and either save that path as an SVG file or simply use that path as the order of plotting for the stipple diagram. | StippleGen is easy-to-use software that can generate TSP and stipple drawings from input images. It saves its files as editable, Eggbot-ready Inkscape SVG files, which can in turn be opened by other vector graphics programs, or re-saved as PDF files for use in other contexts. It can also generate a TSP path from the stippled image, and either save that path as an SVG file or simply use that path as the order of plotting for the stipple diagram. | ||
− | You can read an extended [http://www.evilmadscientist.com/article.php/stipple introduction to StippleGen] at Evil Mad Scientist Laboratories | + | You can read an extended [http://www.evilmadscientist.com/article.php/stipple introduction to StippleGen] at Evil Mad Scientist Laboratories. |
+ | == Download == | ||
− | == | + | StippleGen is free and open source software, written in the [http://processing.org/ Processing development environment]. It comes ready to run on Mac, Windows, and Linux, and it is [http://code.google.com/p/eggbotcode/downloads/list?can=2&q=stipplegen available for download here]. The current version number is 2.01. |
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+ | (StippleGen is hosted as part of the Eggbot project [http://code.google.com/p/eggbotcode/ on Google Code].) | ||
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+ | The download includes ready-to-run platform-specific versions of StippleGen for Mac, Windows, and Linux, as well as the source code. You will need to have a recent version of [http://java.com/ Java] installed on your computer. If the platform-specific version of the software won't run on your computer, please install Java and try again.) | ||
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== Quick Start == | == Quick Start == | ||
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− | All of | + | All of Stipplegen's controls are accessed through the graphical user interface located in the lower part of the screen, in the gray bar. In what follows, we will go over the usage of the individual controls within the interface. |
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After the initial Voronoi diagram is calculated, StippleGen will display the stipple locations that it has calculated. This "first guess" is usually quite crude— as you can see above — and will improve dramatically as you allow StippleGen to run for a while. | After the initial Voronoi diagram is calculated, StippleGen will display the stipple locations that it has calculated. This "first guess" is usually quite crude— as you can see above — and will improve dramatically as you allow StippleGen to run for a while. | ||
− | ''Aside:'' The calculation of the stipple point locations through Secord's algorithm is an ''iterative'' process. For any given "generation," the process begins with an initial set of points— whether that's the initial set of "sprinkled' points, or the output from the previous generation. The Voronoi diagram of those points is then calculated, and each point is moved to the weighted centroid of its Voronoi cell. That distribution of points then serves as the starting point for the subsequent generation. | + | ''Aside:'' The calculation of the stipple point locations through Secord's algorithm is an ''iterative'' process. For any given "generation," the process begins with an initial set of points— whether that's the initial set of "sprinkled' points, or the output from the previous generation. The Voronoi diagram of those points is then calculated, and each point is moved to the weighted centroid of its Voronoi cell. That distribution of points then serves as the starting point for the subsequent generation.) |
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http://evilmadscience.s3.amazonaws.com/wiki/eggbot/stipplegen/v2docs/plant2k.png | http://evilmadscience.s3.amazonaws.com/wiki/eggbot/stipplegen/v2docs/plant2k.png | ||
− | Shown above are two stipple drawings made from the same image of a corn plant, a sample image | + | Shown above are two stipple drawings made from the same image of a corn plant, a sample image that you can download [http://mrl.nyu.edu/~ajsecord/stipples.html here]. One drawing is made with black dots on a white background, and the other has white dots on a black background. However, each drawing has 2000 dots and the parameters are otherwise identical. In this case, as the source image was predominantly white, the image with the white background is of considerably higher quality, as the dots are concentrated in the area of interest, rather than in the background. |
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− | The TSP ("travelling salesman problem") path is an efficient route plotted between the stipple locations. And, depending on how | + | The TSP ("travelling salesman problem") path is an efficient route plotted between the stipple locations. And, depending on how plan to use StippleGen's output, this part of the process may or may not be important to you: |
* If you are creating a set of stipple points for use on the Eggbot, the order in which the points are plotted is given by their order in the file. If you allow the TSP path to be calculated— at least until the end of the "rats nest" stage —will dramatically reduce plotting time. | * If you are creating a set of stipple points for use on the Eggbot, the order in which the points are plotted is given by their order in the file. If you allow the TSP path to be calculated— at least until the end of the "rats nest" stage —will dramatically reduce plotting time. | ||
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http://evilmadscience.s3.amazonaws.com/wiki/eggbot/stipplegen/v2docs/plant10kpath_3.png | http://evilmadscience.s3.amazonaws.com/wiki/eggbot/stipplegen/v2docs/plant10kpath_3.png | ||
− | For this path, we've (1) used the white cutoff to hide the background and (2) allowed it to run for a few more minutes. This path probably won't get much better, so it's a good time to save the TSP path file. There are some little defects, but we're probably better off opening up the file in Inkscape at this point to edit away the bad path segments by hand. | + | For this path, we've (1) used the white cutoff to hide the background and (2) allowed it to run for a few more minutes. This path probably won't get much better, so it's probably a good time to save the TSP path file. There are some little defects, but we're probably better off opening up the file in Inkscape at this point to edit away the bad path segments by hand. |
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==== Saving a Stipple Drawing ==== | ==== Saving a Stipple Drawing ==== | ||
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== Source Code == | == Source Code == | ||
− | The StippleGen source code is available | + | The StippleGen source code is available as part of the [http://code.google.com/p/eggbotcode/downloads/list?can=2&q=stipplegen StippleGen .zip file]. To run the code from source, you'll need to download [http://processing.org/ Processing], and install the [http://hg.postspectacular.com/toxiclibs/downloads toxiclibs library] and the [http://www.sojamo.de/libraries/controlP5/ ControlP5 library]. |