mimouchat/srv/src/faviconWriter.js

const fs = require('fs')
    ,Jimp = require('jimp')

    ,COLOR_MESSAGE = 0x96AFFFFF
    ,COLOR_HIGHLIGHT = 0x4C9689FF //rgb(76, 150, 137);

var font = {}
    ,FONTNAME = __dirname +"/../res/absender1.fnt";

FONTNAME = Jimp.FONT_SANS_128_BLACK;

function FaviconWriter() { }

function loadFont(fontname, cb) {
    if (!font[fontname]) {
        Jimp.loadFont(fontname).then((f) => {
            font[fontname] = f;
            cb(f);
        });
    } else {
        cb(font[fontname]);
    }
}

function centerText(image, font, fontHeight, color, text) {
    var imageWidth = image.bitmap.width
        ,imageHeight = image.bitmap.height
        ,fontCalc = new Jimp(imageWidth, imageHeight)
        ,fontPos = {
            minX: Infinity
            ,maxX: -Infinity
            ,minY: Infinity
            ,maxY: -Infinity
        };

    fontCalc.print(font, 0, 0, text);
    for (var i =0; i < imageWidth; i++)
        for (var j =0; j < imageHeight; j++)
            if (fontCalc.getPixelColor(i, j) !== 0x00000000) {
                fontCalc.setPixelColor(color, i, j);
                fontPos.minX = Math.min(fontPos.minX, i);
                fontPos.maxX = Math.max(fontPos.maxX, i);
                fontPos.minY = Math.min(fontPos.minY, j);
                fontPos.maxY = Math.max(fontPos.maxY, j);
            }
    var margin = 10;
    fontPos.minX = Math.max(fontPos.minX -margin, 0);
    fontPos.maxX = Math.min(fontPos.maxX +margin, imageWidth);
    var sourceWidth = fontPos.maxX -fontPos.minX
        ,sourceHeight = fontPos.maxY -fontPos.minY
        ,zoomFactor = Math.min(imageWidth /sourceWidth, fontHeight /sourceHeight);

    fontCalc.crop(fontPos.minX, fontPos.minY, sourceWidth, sourceHeight);
    fontCalc.scale(zoomFactor);

    image.blit(
        fontCalc,       // font printed image
        (imageWidth/2) - (sourceWidth *zoomFactor /2),  // target x
        (imageHeight/2) -(sourceHeight *zoomFactor /2), // target y
        0,   // source x
        0,   // source y
        sourceWidth *zoomFactor,    // source width
        sourceHeight *zoomFactor);  // source height
    return image;
}

function newImage(text, color, cb) {
    loadFont(FONTNAME, (font) => {
        centerText(new Jimp(256, 256), font, 236, color, text)
            .getBuffer(Jimp.MIME_PNG, (_, buf) => {
                cb(buf);
            });
    });
}

/**
 * @param {number} unreadHi
 * @param {number} unread
 * @param {http.ServerResponse} res
**/
FaviconWriter.write = function(unreadHi, unread, cb) {
    if (unreadHi) {
        newImage('!' +unreadHi, COLOR_HIGHLIGHT, cb);
    } else if (unread) {
        newImage('' +unread, COLOR_MESSAGE, cb);
    } else {
        try {
            var stat = fs.statSync("public/favicon_ok.png")
            res.setHeader('Content-Length', stat.size);
            res.writeHeader("200");
            fs.createReadStream("public/favicon_ok.png").pipe(res, { end: true });
        } catch (e) {
            console.error("WTF cannot find favicon_ok.png in public dir");
            res.writeHeader("404", "Not Found");
            res.end();
        }
    }
};

module.exports = { FaviconWriter: FaviconWriter };