Better resize methods (#498)

* Port resize to wasm

* Expose resize algorithms

* Lanczos3 working!

* lol copy paste

* Adding support for other resizers

* Don’t track generated README

* Cache wasm instance

codecs/resize/src/lib.rs

@@ -0,0 +1,52 @@
+extern crate cfg_if;
+extern crate resize;
+extern crate wasm_bindgen;
+
+mod utils;
+
+use cfg_if::cfg_if;
+use resize::Pixel::RGBA;
+use resize::Type;
+use wasm_bindgen::prelude::*;
+
+cfg_if! {
+    // When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
+    // allocator.
+    if #[cfg(feature = "wee_alloc")] {
+        extern crate wee_alloc;
+        #[global_allocator]
+        static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
+    }
+}
+
+#[wasm_bindgen]
+#[no_mangle]
+pub fn resize(
+    input_image: Vec<u8>,
+    input_width: usize,
+    input_height: usize,
+    output_width: usize,
+    output_height: usize,
+    typ_idx: usize,
+) -> Vec<u8> {
+    let typ = match typ_idx {
+        0 => Type::Triangle,
+        1 => Type::Catrom,
+        2 => Type::Mitchell,
+        3 => Type::Lanczos3,
+        _ => panic!("Nope"),
+    };
+    let num_output_pixels = output_width * output_height;
+    let mut resizer = resize::new(
+        input_width,
+        input_height,
+        output_width,
+        output_height,
+        RGBA,
+        typ,
+    );
+    let mut output_image = Vec::<u8>::with_capacity(num_output_pixels * 4);
+    output_image.resize(num_output_pixels * 4, 0);
+    resizer.resize(input_image.as_slice(), output_image.as_mut_slice());
+    return output_image;
+}