https://github.com/icholy/caps

Attempt at making computer generated pixel art from bottle caps
https://github.com/icholy/caps

Last synced: 1 day ago
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Attempt at making computer generated pixel art from bottle caps

• Host: GitHub
• URL: https://github.com/icholy/caps
• Owner: icholy
• Created: 2022-02-04T18:26:27.000Z (over 2 years ago)
• Default Branch: master
• Last Pushed: 2022-02-04T18:27:00.000Z (over 2 years ago)
• Last Synced: 2024-06-21T18:56:21.924Z (3 months ago)
• Language: Go
• Homepage:
• Size: 23.2 MB
• Stars: 3
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        

I started sorting the caps and realised that there are significantly more Alexander Keiths than anything else. Counting them while sorting was something I considered, but it was harder than you'd think. The plan is to use a scale to weigh them and avoid having to count at all.

![](images/sorting.JPG)

These are the main caps. The individual cropped photos can be found in the `images/caps/` directory. The two budwiser cap types are pretty similar but I decided to keep them separate just in case. Mixing them is a lot easier than re-sorting.

![](images/cropped.png)

While I figure out where to find a scale, I might as well start thinking about the cap layout. The `shape` and `pattern` packages define some simple layout algorithms. This is the output of the `pattern.Grid` implementation.

![](images/grid_pattern.png)

This seemed ok until I started actually arranging the caps manually. The pattern wasn't a square grid at all...

![](images/packed_caps.JPG)

A bit of googling I found that it's called [Circle Packing](https://en.wikipedia.org/wiki/Circle_packing). A set of 3 touching caps can be viewed as an equilateral triangle with a point at the center of each cap. Each side is two times the radius of a cap so all we need is the Pythagorean Theorem for this one.

![](images/circle_packing_whiteboard.JPG)

 

Based on this, I implemented `pattern.Triangular`. Here's an example of the output.

![](images/triangular_pattern.png)

Time to see how this might actually work. This is the source image I'm working with:

![](images/rubik_cube.png)

I set the circle radius to be 20 pixels which results in 1863 circles. For each circle, I am taking the bounding box and padding it with 5 additiona pixels. I'm then computing the average RGB color for that rectangle in the source image. Finally, I draw the circle with the color as the fill.

![](images/rubik_cube_bounds_averaging.png)

Now let's replace the circles with bottlecaps! I'm choosing a bottle cap image by comparing the circle color with the cap image's average color. The huristic is pretty simplistic: `DISTANCE = ABS(a.R - b.R) + ABS(a.G - b.G) + ABS(a.B - b.B)`.

![](images/rubik_cube_avg_color_caps.png)

Not what we wanted ... I'm assuming the color difference function is too shitty. I found the Wikipedia page for [Color Difference](https://en.wikipedia.org/wiki/Color_difference) and it says that I should be using a weighted Euclidean distance function. That's basically what I was doing before except you square each component difference before adding and then take the square root of the sum. Since I'm just comparing them, I can skip the last step. 

![](images/rubik_cube_weighted_avg.png)

I tried a different approach to color selection. First I find N prominent colors in the image (using k-means) where N is number of cap types (in our case 6). Then I match each promiment color to a bottlecap that has a similar color (each color is only used once). This seems to produce better contrast in certain features. I also stopped drawing caps in tiles with no pixels. I'll need to figure out how to deal with those edges.

![](images/rubik_cube_kmeans.png)

Someone threw out all the caps, so I'm not going to be working on this anymore.