imagescript/wasm/node/svg.js

zero-dependency javascript image manipulation

const wasm_name = 'svg';
const { join } = require('path');
const { promises: { readFile } } = require('fs');
const wasm_path = process.env.IMAGESCRIPT_WASM_SIMD ? 'simd' : 'any';

let mod = null;
module.exports = {
  async init() {
    if (!mod) mod = new WebAssembly.Module(await readFile(join(__dirname, `../${wasm_path}/${wasm_name}.wasm`)));

    return this.new();
  },

  new() {
    const wasm = new WebAssembly.Instance(mod).exports;

    class mem {
      static length() { return wasm.wlen(); }
      static alloc(size) { return wasm.walloc(size); }
      static free(ptr, size) { return wasm.wfree(ptr, size); }
      static u8(ptr, size) { return new Uint8Array(wasm.memory.buffer, ptr, size); }
      static u32(ptr, size) { return new Uint32Array(wasm.memory.buffer, ptr, size); }

      static copy_and_free(ptr, size) {
        let slice = mem.u8(ptr, size).slice();
        return (wasm.wfree(ptr, size), slice);
      }
    }

    function load(buffer, fit) {
      if (!fit) return rasterize(buffer, 0, 0);
      if (fit.zoom) return rasterize(buffer, 1, fit.zoom);
      if (fit.width) return rasterize(buffer, 2, fit.width);
      if (fit.height) return rasterize(buffer, 3, fit.height);
    }

    function rasterize(buffer, fit, scale) {
      const bptr = mem.alloc(buffer.length);
      mem.u8(bptr, buffer.length).set(buffer);
      const ptr = wasm.rasterize(bptr, buffer.length, fit, scale);

      if (0 === ptr) throw new Error('svg: failed to parse');
      if (1 === ptr) throw new Error('svg: failed to rasterize');

      const framebuffer = {
        width: wasm.rasterize_width(ptr),
        height: wasm.rasterize_height(ptr),
        buffer: mem.u8(wasm.rasterize_buffer(ptr), mem.length()).slice(),
      }

      return (wasm.rasterize_free(ptr), framebuffer);
    }

    return { load, rasterize };
  }
}