image_processor.js

"use strict";

let gm = require("gm");
let os = require("os");
let fs = require("fs");
let promisify = require("es6-promisify");
let imageSize = promisify(require("image-size"));
let Gmsmith = require("gmsmith");
let concat = require("concat-stream");
let promiseLimit = require("promise-limit");

module.exports = class ImageProcessor{
    constructor() {
        this.gm = gm.subClass({ imageMagick: true });
    }

    getSize(path) {
        return imageSize(path);
    }

    scale(input, output, scale) {
        let resized = this.gm(input)
        .resizeExact(scale.width, scale.height);
        return promisify(resized.write.bind(resized))(output);
    }

    trim(input, output, fuzz) {
        fuzz = fuzz || "0%";

        let imageWithBorder = this.gm(input)
        .borderColor("none")
        .border(1, 1);

        return promisify(imageWithBorder.toBuffer.bind(imageWithBorder))()
        .then((data) => {
            let image = this.gm(data).trim();
            return promisify(image.identify.bind(image))("%@");
        })
        .then((data) => {
            data = data.match(/^(\d+)x(\d+)\+(\d+)\+(\d+)$/);
            var width = parseInt(data[1], 10);
            var height = parseInt(data[2], 10);
            var x = parseInt(data[3], 10) - 1;
            var y = parseInt(data[4], 10) - 1;

            if(width === 0 && height === 0) {
                return false;
            }

            if (width === 0 || height === 0) {
                width = 1;
                height = 1;
                x = 0;
                y = 0;
            }

            var crop = this.gm(input)
                .crop(width, height, x, y);
            return promisify(crop.write.bind(crop))(output)
            .then(() => { return {width, height, x, y}; });
        });
    };

    combine(rects, width, height, outputFileName, jpeg, quality, compressor) {
        let exportOptions = {format: jpeg ? "jpeg" : "png"};
        if (jpeg && quality) {
            exportOptions.quality = quality;
        }
        let gmsmith = new Gmsmith({});
        let paths = rects.map(rect => rect.data.path);

        return promisify(gmsmith.createImages.bind(gmsmith))(paths)
        .then(images => {
            let canvas = gmsmith.createCanvas(width, height);

            images.forEach((image, i) => {
                canvas.addImage(image, rects[i].x, rects[i].y);
            });

            let stream = canvas.export(exportOptions);
            return new Promise((resolve, reject) => {
                stream.on("error", reject);
                stream.pipe(concat({encoding: "buffer"}, resolve))
            })
        })
        .then(buffer => compressor ? compressor(buffer) : buffer)
        .then(buffer => promisify(fs.writeFile)(outputFileName, buffer));
    }
};