image-tiler/index.js

Create zoom tile pyramids from a large image

'use strict';
var execFileSync = require('child_process').execFileSync;
var sizeOf = require('image-size');
var mkdirp = require('mkdirp-promise');
var rimraf = require('rimraf-then');
var fs = require('fs');
var path = require('path');

function tileLevel(inPath, outPath, zoom, tileSize, pattern, quality) {
    var dotExtension = pattern.replace(/.*(\.[^.]+)$/, '$1');
    var patternedFilename = pattern.replace(/\{z\}/, '' + zoom)
        .replace(/\{x\}/, '%[fx:page.x/' + tileSize + ']')
        .replace(/\{y\}/, '%[fx:page.y/' + tileSize + ']')
        .replace(/\.[^.]+$/, '');
    var patternedFilenameWithoutTheFilename = '';
    if (pattern.indexOf(path.sep) > 0) {
        patternedFilenameWithoutTheFilename = pattern.replace(new RegExp(path.sep + '[^' + path.sep + ']*$'), '')
            .replace(/\{z\}/, '' + zoom);
    }
    return mkdirp(outPath + path.sep + patternedFilenameWithoutTheFilename)
        .then(() => {
            var args = [inPath,
                '-crop', tileSize + 'x' + tileSize,
                '-set', 'filename:tile', patternedFilename,
                '-quality', quality, '+repage', '+adjoin',
                outPath + '/%[filename:tile]' + dotExtension];
            execFileSync('convert', args);
        });
}

function imageBiggerThanTile(path, tileSize) {
    var size = sizeOf(path);
    return size.height > tileSize || size.width > tileSize;
}

function tileRec(inPath, outPath, zoom, tileSize, tempDir, pattern, zoomToDisplay, invertZoom, quality) {
    var inPathMpc = tempDir + '/temp_level_' + zoom + '.mpc';
    var inPathCache = tempDir + '/temp_level_' + zoom + '.cache';
    execFileSync('convert', [inPath, inPathMpc]);
    return tileLevel(inPathMpc, outPath, zoomToDisplay, tileSize, pattern, quality)
        .then(function () {
            if (imageBiggerThanTile(inPath, tileSize)) {
                var newZoom = zoom + 1;
                var newZoomToDisplay = zoomToDisplay + 1;
                if (!invertZoom) {
                    newZoomToDisplay = zoomToDisplay - 1;
                }
                var newInPath = tempDir + '/temp_level_' + zoom + '.png';
                execFileSync('convert', [inPathMpc, '-resize', '50%', '-quality', quality, newInPath]);
                fs.unlinkSync(inPathMpc);
                fs.unlinkSync(inPathCache);
                return tileRec(newInPath, outPath, newZoom, tileSize, tempDir, pattern, newZoomToDisplay, invertZoom, quality);
            } else {
                fs.unlinkSync(inPathMpc);
                fs.unlinkSync(inPathCache);
            }
        });
}

module.exports.tile = function (inPath, outPath, pattern, options) {
    options = options || {};
    var tileSize = options.tileSize || 256;
    var tmpDir = options.tmpDir || process.env.TMPDIR || '/tmp';
    var tempDir = tmpDir + '/image-tiler_' + process.pid;
    var zoom = 0;
    var zoomToDisplay = 0;
    var quality = options.quality || 100;
    if (!options.invertZoom) {
        var size = sizeOf(inPath);
        var halvingsWidth = Math.ceil(Math.log2(Math.ceil(size.width / tileSize)));
        var halvingsheight = Math.ceil(Math.log2(Math.ceil(size.height / tileSize)));
        zoomToDisplay = Math.max(halvingsWidth, halvingsheight);
    }
    return mkdirp(tempDir)
        .then(() => tileRec(inPath, outPath, zoom, tileSize, tempDir, pattern, zoomToDisplay, options.invertZoom, quality))
        .then(() => rimraf(tempDir));
};