readme.md: add description of image_matcher.go

README.md

@@ -58,3 +58,33 @@ D" 	 84
 151.88245ms
 ```
 You can see the string slowly becoming more like the input string as there are more iterations.
+
+#### examples/image_matcher.go
+To run:
+```
+cd examples
+go run image_matcher.go <path_to_image>
+```
+
+Image matcher takes an input image and attempts to produce an output image that is as close to it as possible only using RGBA coloured rectangles and circles. There are a few parameters at the top of the file that are interesting to fiddle with:
+```
+kNumShapes = 100
+kPopulationSize = 1000
+kMaxIterations = 9999999
+kBitsPerCoordinateNumber = 9
+kParallelSimulations = 24
+kMaxCircleRadiusFactor = 3
+```
+* kNumShapes - the number of shapes that are used when the algorithm re-creates the input image
+* kPopulationSize - the number of genomes in each population. Each genome can be decoded into a picture. A high value will mean each iteration takes longer, and usually results in the algorithm finding its optimal solution in less iterations.
+* kMaxIterations - the maximum number of simulations/iterations to run. Providing a huge number will essentially run until the algorithm has figured out what it thinks is an optimal solution.
+* kBitsPerCoordinateNumber - Each shape is positioned using coordinates. A rect is represented by the top left and bottom right coordinates, and a circle by its centre. A coordinate is made up of two numbers, each number is represented by this many bits. The number generated is used to calculate a percentage of the overall width/height of the image for the coordinate to be positioned at. For example, if kBitsPerCoordinateNumber is 8, that means the maximum value a coordinte can be is ```0b11111111```, or ```255```. To calculate the coordinates number relative to the image's width and height we normalise this and apply the decimal to the pictures dimensions. For example, if our X coordinate produced by the algorithm is 233, and our images width is 120. ```( 233 / 255 ) * 120 == 109 == our X coordinate```. Setting this to a high value means the algorithm has more accuracy when placing shapes. A low value of 2 or 3 also creates some interesting effects.
+* kParallelSimulations - The number of simulations to run in parallel. A higher value usually means each iteration takes less time, up to a certain point.
+* kMaxCircleRadiusFactor - A number to divide a circles radius by. 1 will mean a circles radius can be anywhere between 1 and max( inputImageWidth, inputImageHeight ). From experimenting, restricting the radius a little creates 'better' images quicker
+
+The script outputs the 'best' genome from each iteration to "elite.png" as well as the original overlayed in "elite_with_original.png".
+
+Here's an example of what can be generated. Input, output and both overlayed over the top of each other:
+![input](https://cloud.githubusercontent.com/assets/5236109/10744734/01031bda-7c34-11e5-94ab-795afba114c1.gif)
+![output](https://cloud.githubusercontent.com/assets/5236109/10744673/97a7aea8-7c33-11e5-8cfe-ea66489d8d9c.png)
+![overlayed](https://cloud.githubusercontent.com/assets/5236109/10744674/9ad23fa8-7c33-11e5-88d9-aff565cca6c4.png)