mirror of https://github.com/CesiumGS/obj2gltf.git
102 lines
2.9 KiB
JavaScript
102 lines
2.9 KiB
JavaScript
'use strict';
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var Cesium = require('cesium');
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var fs = require('fs-extra');
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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 fsReadFile = Promise.promisify(fs.readFile);
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var defaultValue = Cesium.defaultValue;
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var WebGLConstants = Cesium.WebGLConstants;
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module.exports = loadImage;
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/**
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* Load an image file and get information about it.
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*
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* @param {String} imagePath Path to the image file.
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* @param {Object} [options] An object with the following properties:
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* @param {Boolean} [options.checkTextureAlpha=false] Do a more exhaustive check for texture transparency by looking at the alpha channel of each pixel.
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* @returns {Promise} A promise resolving to the image information, or undefined if the file doesn't exist.
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*
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* @private
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*/
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function loadImage(imagePath, options) {
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options = defaultValue(options, defaultValue.EMPTY_OBJECT);
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var checkTextureAlpha = defaultValue(options.checkTextureAlpha, false);
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return fsReadFile(imagePath)
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.then(function(data) {
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var extension = path.extname(imagePath);
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var info = {
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transparent : false,
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format : getFormat(3),
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source : data,
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extension : extension
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};
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if (extension === '.png') {
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// Color type is encoded in the 25th bit of the png
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var colorType = data[25];
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var channels = getChannels(colorType);
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info.format = getFormat(channels);
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if (channels === 4) {
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if (checkTextureAlpha) {
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info.transparent = isTransparent(data);
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} else {
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info.transparent = true;
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}
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}
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}
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return info;
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})
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.catch(function() {
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console.log('Could not read image file at ' + imagePath + '. Material will ignore this image.');
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return undefined;
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});
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}
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function isTransparent(data) {
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var decoded = PNG.sync.read(data);
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var pixels = decoded.data;
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var pixelsLength = decoded.width * decoded.height;
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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 getFormat(channels) {
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switch (channels) {
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case 1:
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return WebGLConstants.ALPHA;
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case 2:
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return WebGLConstants.LUMINANCE_ALPHA;
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case 3:
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return WebGLConstants.RGB;
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case 4:
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return WebGLConstants.RGBA;
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}
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}
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