sunnuntai 31. maaliskuuta 2019

JS1k 2019 writeup part 3 - Strigiformes

Most of my better known wildlife images are of owls and birds of prey have fascinated me since I was a little boy. Once while going through images on Pinterest I saw a cool art design where feathers had owl heads. It was created by Oleksandra Barysheva and can be seen on her Threadless page. I decided to try and do my version of it and see how many recognizable owls I could fit in 1024 bytes of JavaScript...

1. Feather function

To draw one side of the feather we first build two nested loops. Inner loop draws a single barb away from the shaft while the outer loop moves us upwards to the next starting position.


The above code shows the basic loop structure. Then step by step we begin to add rules for the barb length and make them curve resulting in a very natural looking shape...

We then put this loop inside a function which allows us to use arguments for variation. To create the other side of the feather we can use scale(-1,1) to flip the x-axis and then call our function again.

Now that we are happy with the shape of the feather we can add colors. We make the brightness change based on the values of loop iterators. The shaft and first barbs need to be white. A nice gradient for the length of the barb and some natural looking variation and our feather function is complete.

2. Drawing the head in layers

To start the owl's head we use arc to draw an unfinished circle. On top of that we draw darker colored rays shooting out from the center. The tricky part is creating a loop to draw the two discs that are characteristic of owls. Eyes are in the center of these discs. Color of pixels change as we go further away from the center. Texture is achieved by adding smaller scale contrast changes using remainder. Eyebrows are done in similar fashion on top of the disc. Last but not least we do the peak with two small rects...

3. Repeating code

One of the strategies to fit a lot of code into 1kb is making different parts of the code look the same. The packer can heavily compress these repetitions. After I had done the great grey owl I repeated the same code and made just enough changes so that the next owl would be recognizable. I kept doing more species until I was out of space. To finalize the demo I grouped the owls nicely instead of having them in a line. I also came up with a variation to the feathers so it would look like some of the owls are spreading their wings.

Follow me on Twitter if you want to hear of new demos and blog updates - @jylikangas

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