spritemap.js

const gm = require('gm');
const fse = require('fs-extra');
const path = require('path');

module.exports = (sheets, cache = '.spritemap-cache/') => {
  fse.ensureDir(cache).then(() =>
    sheets.forEach((configPath) => fse.readJson(configPath).then((data) => {
      console.log('Reading ' + configPath);
      const basePath = path.dirname(configPath);
      const inputPath = path.join(basePath, data.input.path);
      const inputExt = data.input.extension || 'png';
      const { x: basisX, y: basisY } = data.basis;
      const { x: gridX, y: gridY } = data.grid;
      const sprites = data.sprites;
      const blocks = data.blocks;
      const tempPath = path.join(cache, data.output.path);
      console.log('Writing ' + tempPath);
      const ox = basisX * gridX;
      const oy = basisY * gridY;

      const getValues = (data) => {
        const { x: gx, y: gy, src } = data;
        const gw = data.w || 1;
        const gh = data.h || 1;
        const px = gx * (basisX + 0);
        const py = gy * (basisY + 0);
        const pw = gw * basisX;
        const ph = gh * basisY;

        const imgSrc = `${src}.${inputExt}`;
        const srcPath = path.join(inputPath, imgSrc);
        const tmpPath = path.join(cache, imgSrc);
        return {
          gx, gy, gw, gh, px, py, pw, ph, imgSrc, srcPath, tmpPath,
        };
      }

      const bufferX = sprites.map(v => (v.w || 1) * basisX).reduce((a, b) => a > b ? a : b, 0);
      const bufferY = sprites.map(v => (v.h || 1) * basisY).reduce((a, b) => a > b ? a : b, 0);
      console.log('bufferX: '+ bufferX + ' bufferY: ' + bufferY); // Needs a buffer zone because region().draw() overrites from 0,0 for some reason

      const serialStitch = (array, buffer, position) => {
        if (position === array.length) {
          gm(buffer)
            .crop(ox, oy, bufferX, bufferY)
            .write(tempPath, err => {
              if (err) console.log('no write: '+ tempPath + `\n${err}`);
            });
        } else {

          const { gx, gy, gw, gh, px, py, pw, ph, imgSrc, srcPath, tmpPath } = getValues(array[position]);

          if (!fse.existsSync(srcPath)) {
            console.log('DNE:', srcPath, '->', tempPath);
            serialStitch(array, buffer, position + 1);
          } else {
            gm(buffer)
              .region(pw, ph, px + bufferX, py + bufferY)
              .draw(`image Over ${0},${0} ${pw},${ph} ${srcPath}`)
              .region(ox + bufferX, oy + bufferY, -px - bufferX, -py - bufferY) // required because gm draw bleeds one column to the right and the left-most pixel below
              .toBuffer('PNG', (err, buf) => {
                serialStitch(array, buf, position + 1); // TODO convert to actual iterative
              });
          }
        }
      };

      gm(ox + bufferX, oy + bufferY, "transparent")
        .toBuffer('png', (err, buffer) => {
          if (err) console.log(err);
          serialStitch(sprites, buffer, 0);
        });
    })));

}