adds julia set example (#419)

* adds julia set example

* fixes indentation in *.js files

* fixes *.js formatting

* fixes a typo in function arguments signature

examples/julia_set/src/fractal/complex/mod.rs

@@ -0,0 +1,27 @@
+use std::ops::Add;
+
+#[derive(Clone, Copy, Debug)]
+pub struct Complex {
+  pub real: f64,
+  pub imaginary: f64,
+}
+
+impl Complex {
+  pub fn square(self) -> Complex {
+    let real = (self.real * self.real) - (self.imaginary * self.imaginary);
+    let imaginary = 2.0 * self.real * self.imaginary;
+    Complex { real, imaginary }
+  }
+
+  pub fn norm(&self) -> f64 {
+    (self.real * self.real) + (self.imaginary * self.imaginary)
+  }
+}
+
+impl Add<Complex> for Complex {
+  type Output = Complex;
+
+  fn add(self, rhs: Complex) -> Complex {
+    Complex { real: self.real + rhs.real, imaginary: self.imaginary + rhs.imaginary }
+  }
+}

examples/julia_set/src/fractal/mod.rs

@@ -0,0 +1,36 @@
+pub mod complex;
+use self::complex::Complex;
+
+fn get_iter_index(z: Complex, c: Complex) -> u32 {
+  let mut iter_index: u32 = 0;
+  let mut z = z;
+  while iter_index < 900 {
+    if z.norm() > 2.0 {
+      break
+    }
+    z = z.square() + c;
+    iter_index += 1;
+  }
+  iter_index
+}
+
+pub fn get_julia_set(width: u32, height: u32, c: Complex) -> Vec<u8> {
+  let mut data: Vec<u8> = vec![];
+    
+  let param_i = 1.5;
+  let param_r = 1.5;
+  let scale = 0.005;
+
+  for x in 0..width {
+    for y in 0..height {
+      let z = Complex { real: y as f64 * scale - param_r, imaginary: x as f64 * scale - param_i };
+      let iter_index = get_iter_index(z, c);
+      data.push((iter_index / 4) as u8);
+      data.push((iter_index / 2) as u8);
+      data.push(iter_index as u8);
+      data.push(255);
+    }
+  }
+
+  data
+}

examples/julia_set/src/lib.rs

@@ -0,0 +1,41 @@
+#![feature(proc_macro, wasm_custom_section, wasm_import_module, js_globals)]
+
+extern crate wasm_bindgen;
+use wasm_bindgen::prelude::*;
+
+mod fractal;
+use fractal::get_julia_set;
+use fractal::complex::Complex;
+
+#[wasm_bindgen]
+extern "C" {
+    pub type ImageData;
+
+    #[wasm_bindgen(constructor)]
+    pub fn new(arr: &Uint8ClampedArray, width: u32, height: u32) -> ImageData;
+}
+
+#[wasm_bindgen]
+extern "C" {
+    pub type Uint8ClampedArray;
+
+    #[wasm_bindgen(constructor)]
+    pub fn new(arr: &[u8]) -> Uint8ClampedArray;
+}
+
+#[wasm_bindgen]
+extern "C" {
+    pub type CanvasRenderingContext2D;
+
+    #[wasm_bindgen(method, js_name = putImageData)]
+    pub fn put_image_data(this: &CanvasRenderingContext2D, image_data: &ImageData, p_1: i32, p_2: i32);
+}
+
+#[wasm_bindgen]
+pub fn draw(ctx: &CanvasRenderingContext2D, width: u32, height: u32, real: f64, imaginary: f64) {
+    let c = Complex { real, imaginary };
+    let data = get_julia_set(width, height, c);
+    let uint8_array = Uint8ClampedArray::new(&data);
+
+    ctx.put_image_data(&ImageData::new(&uint8_array, width, height), 0, 0);
+}