mirror of https://github.com/CesiumGS/obj2gltf.git
128 lines
3.9 KiB
JavaScript
128 lines
3.9 KiB
JavaScript
'use strict';
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var Cesium = require('cesium');
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var fsExtra = require('fs-extra');
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var jpeg = require('jpeg-js');
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var path = require('path');
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var PNG = require('pngjs').PNG;
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var Promise = require('bluebird');
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var Texture = require('./Texture');
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var defaultValue = Cesium.defaultValue;
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var defined = Cesium.defined;
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module.exports = loadTexture;
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/**
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* Load a texture file.
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*
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* @param {String} texturePath Path to the texture file.
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* @param {Object} [options] An object with the following properties:
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* @param {Boolean} [options.checkTransparency=false] Do a more exhaustive check for texture transparency by looking at the alpha channel of each pixel.
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* @param {Boolean} [options.decode=false] Whether to decode the texture.
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* @returns {Promise} A promise resolving to a Texture object.
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*
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* @private
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*/
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function loadTexture(texturePath, options) {
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options = defaultValue(options, {});
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options.checkTransparency = defaultValue(options.checkTransparency, false);
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options.decode = defaultValue(options.decode, false);
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return fsExtra.readFile(texturePath)
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.then(function(source) {
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var name = path.basename(texturePath, path.extname(texturePath));
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var extension = path.extname(texturePath).toLowerCase();
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var texture = new Texture();
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texture.source = source;
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texture.name = name;
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texture.extension = extension;
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texture.path = texturePath;
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var decodePromise;
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if (extension === '.png') {
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decodePromise = decodePng(texture, options);
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} else if (extension === '.jpg' || extension === '.jpeg') {
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decodePromise = decodeJpeg(texture, options);
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}
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if (defined(decodePromise)) {
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return decodePromise.thenReturn(texture);
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}
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return texture;
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});
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}
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function hasTransparency(pixels) {
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var pixelsLength = pixels.length / 4;
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for (var i = 0; i < pixelsLength; ++i) {
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if (pixels[i * 4 + 3] < 255) {
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return true;
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}
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}
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return false;
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}
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function getChannels(colorType) {
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switch (colorType) {
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case 0: // greyscale
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return 1;
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case 2: // RGB
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return 3;
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case 4: // greyscale + alpha
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return 2;
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case 6: // RGB + alpha
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return 4;
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default:
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return 3;
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}
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}
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function parsePng(data) {
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return new Promise(function(resolve, reject) {
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new PNG().parse(data, function(error, decodedResults) {
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if (defined(error)) {
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reject(error);
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return;
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}
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resolve(decodedResults);
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});
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});
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}
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function decodePng(texture, options) {
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// Color type is encoded in the 25th bit of the png
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var source = texture.source;
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var colorType = source[25];
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var channels = getChannels(colorType);
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var checkTransparency = (channels === 4 && options.checkTransparency);
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var decode = options.decode || checkTransparency;
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if (decode) {
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return parsePng(source)
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.then(function(decodedResults) {
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if (options.checkTransparency) {
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texture.transparent = hasTransparency(decodedResults.data);
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}
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if (options.decode) {
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texture.pixels = decodedResults.data;
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texture.width = decodedResults.width;
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texture.height = decodedResults.height;
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texture.source = undefined; // Unload resources
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}
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});
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}
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}
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function decodeJpeg(texture, options) {
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if (options.decode) {
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var source = texture.source;
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var decodedResults = jpeg.decode(source);
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texture.pixels = decodedResults.data;
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texture.width = decodedResults.width;
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texture.height = decodedResults.height;
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texture.source = undefined; // Unload resources
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}
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}
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