[Files.app] Split the JavaScript files into subdirectories: common, background, and foreground

chrome/browser/resources/file_manager/js/image_editor/image_encoder.js

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-'use strict';
-
-/**
- * A namespace class for image encoding functions. All methods are static.
- */
-function ImageEncoder() {}
-
-/**
- * @type {Array.<Object>}
- */
-ImageEncoder.metadataEncoders = {};
-
-/**
- * @param {function(new:ImageEncoder.MetadataEncoder)} constructor
- *     // TODO(JSDOC).
- * @param {string} mimeType  // TODO(JSDOC).
- */
-ImageEncoder.registerMetadataEncoder = function(constructor, mimeType) {
-  ImageEncoder.metadataEncoders[mimeType] = constructor;
-};
-
-/**
- * Create a metadata encoder.
- *
- * The encoder will own and modify a copy of the original metadata.
- *
- * @param {Object} metadata Original metadata.
- * @return {ImageEncoder.MetadataEncoder} Created metadata encoder.
- */
-ImageEncoder.createMetadataEncoder = function(metadata) {
-  var constructor = ImageEncoder.metadataEncoders[metadata.mimeType] ||
-      ImageEncoder.MetadataEncoder;
-  return new constructor(metadata);
-};
-
-
-/**
- * Create a metadata encoder object holding a copy of metadata
- * modified according to the properties of the supplied image.
- *
- * @param {Object} metadata Original metadata.
- * @param {HTMLCanvasElement} canvas Canvas to use for metadata.
- * @param {number} quality Encoding quality (defaults to 1).
- * @return {ImageEncoder.MetadataEncoder} Encoder with encoded metadata.
- */
-ImageEncoder.encodeMetadata = function(metadata, canvas, quality) {
-  var encoder = ImageEncoder.createMetadataEncoder(metadata);
-  encoder.setImageData(canvas);
-  encoder.setThumbnailData(ImageEncoder.createThumbnail(canvas), quality || 1);
-  return encoder;
-};
-
-
-/**
- * Return a blob with the encoded image with metadata inserted.
- * @param {HTMLCanvasElement} canvas The canvas with the image to be encoded.
- * @param {ImageEncoder.MetadataEncoder} metadataEncoder Encoder to use.
- * @param {number} quality (0..1], Encoding quality, defaults to 0.9.
- * @return {Blob} encoded data.
- */
-ImageEncoder.getBlob = function(canvas, metadataEncoder, quality) {
-  // Contrary to what one might think 1.0 is not a good default. Opening and
-  // saving an typical photo taken with consumer camera increases its file size
-  // by 50-100%.
-  // Experiments show that 0.9 is much better. It shrinks some photos a bit,
-  // keeps others about the same size, but does not visibly lower the quality.
-  quality = quality || 0.9;
-
-  ImageUtil.trace.resetTimer('dataurl');
-  // WebKit does not support canvas.toBlob yet so canvas.toDataURL is
-  // the only way to use the Chrome built-in image encoder.
-  var dataURL =
-      canvas.toDataURL(metadataEncoder.getMetadata().mimeType, quality);
-  ImageUtil.trace.reportTimer('dataurl');
-
-  var encodedImage = ImageEncoder.decodeDataURL(dataURL);
-
-  var encodedMetadata = metadataEncoder.encode();
-
-  var slices = [];
-
-  // TODO(kaznacheev): refactor |stringToArrayBuffer| and |encode| to return
-  // arrays instead of array buffers.
-  function appendSlice(arrayBuffer) {
-    slices.push(new DataView(arrayBuffer));
-  }
-
-  ImageUtil.trace.resetTimer('blob');
-  if (encodedMetadata.byteLength != 0) {
-    var metadataRange = metadataEncoder.findInsertionRange(encodedImage);
-    appendSlice(ImageEncoder.stringToArrayBuffer(
-        encodedImage, 0, metadataRange.from));
-
-    appendSlice(metadataEncoder.encode());
-
-    appendSlice(ImageEncoder.stringToArrayBuffer(
-        encodedImage, metadataRange.to, encodedImage.length));
-  } else {
-    appendSlice(ImageEncoder.stringToArrayBuffer(
-        encodedImage, 0, encodedImage.length));
-  }
-  var blob = new Blob(slices, {type: metadataEncoder.getMetadata().mimeType});
-  ImageUtil.trace.reportTimer('blob');
-  return blob;
-};
-
-/**
- * Decode a dataURL into a binary string containing the encoded image.
- *
- * Why return a string? Calling atob and having the rest of the code deal
- * with a string is several times faster than decoding base64 in Javascript.
- *
- * @param {string} dataURL Data URL to decode.
- * @return {string} A binary string (char codes are the actual byte values).
- */
-ImageEncoder.decodeDataURL = function(dataURL) {
-  // Skip the prefix ('data:image/<type>;base64,')
-  var base64string = dataURL.substring(dataURL.indexOf(',') + 1);
-  return atob(base64string);
-};
-
-/**
- * Return a thumbnail for an image.
- * @param {HTMLCanvasElement} canvas Original image.
- * @param {number=} opt_shrinkage Thumbnail should be at least this much smaller
- *     than the original image (in each dimension).
- * @return {HTMLCanvasElement} Thumbnail canvas.
- */
-ImageEncoder.createThumbnail = function(canvas, opt_shrinkage) {
-  var MAX_THUMBNAIL_DIMENSION = 320;
-
-  opt_shrinkage = Math.max(opt_shrinkage || 4,
-                       canvas.width / MAX_THUMBNAIL_DIMENSION,
-                       canvas.height / MAX_THUMBNAIL_DIMENSION);
-
-  var thumbnailCanvas = canvas.ownerDocument.createElement('canvas');
-  thumbnailCanvas.width = Math.round(canvas.width / opt_shrinkage);
-  thumbnailCanvas.height = Math.round(canvas.height / opt_shrinkage);
-
-  var context = thumbnailCanvas.getContext('2d');
-  context.drawImage(canvas,
-      0, 0, canvas.width, canvas.height,
-      0, 0, thumbnailCanvas.width, thumbnailCanvas.height);
-
-  return thumbnailCanvas;
-};
-
-/**
- * TODO(JSDOC)
- * @param {string} string  // TODO(JSDOC).
- * @param {number} from  // TODO(JSDOC).
- * @param {number} to  // TODO(JSDOC).
- * @return {ArrayBuffer}  // TODO(JSDOC).
- */
-ImageEncoder.stringToArrayBuffer = function(string, from, to) {
-  var size = to - from;
-  var array = new Uint8Array(size);
-  for (var i = 0; i != size; i++) {
-    array[i] = string.charCodeAt(from + i);
-  }
-  return array.buffer;
-};
-
-/**
- * A base class for a metadata encoder.
- *
- * Serves as a default metadata encoder for images that none of the metadata
- * parsers recognized.
- *
- * @param {Object} original_metadata Starting metadata.
- * @constructor
- */
-ImageEncoder.MetadataEncoder = function(original_metadata) {
-  this.metadata_ = MetadataCache.cloneMetadata(original_metadata) || {};
-  if (this.metadata_.mimeType != 'image/jpeg') {
-    // Chrome can only encode JPEG and PNG. Force PNG mime type so that we
-    // can save to file and generate a thumbnail.
-    this.metadata_.mimeType = 'image/png';
-  }
-};
-
-/**
- * TODO(JSDOC)
- * @return {Object}   // TODO(JSDOC).
- */
-ImageEncoder.MetadataEncoder.prototype.getMetadata = function() {
-  return this.metadata_;
-};
-
-/**
- * @param {HTMLCanvasElement|Object} canvas Canvas or or anything with
- *                                          width and height properties.
- */
-ImageEncoder.MetadataEncoder.prototype.setImageData = function(canvas) {
-  this.metadata_.width = canvas.width;
-  this.metadata_.height = canvas.height;
-};
-
-/**
- * @param {HTMLCanvasElement} canvas Canvas to use as thumbnail.
- * @param {number} quality Thumbnail quality.
- */
-ImageEncoder.MetadataEncoder.prototype.setThumbnailData =
-    function(canvas, quality) {
-  this.metadata_.thumbnailURL =
-      canvas.toDataURL(this.metadata_.mimeType, quality);
-};
-
-/**
- * Return a range where the metadata is (or should be) located.
- * @param {string} encodedImage // TODO(JSDOC).
- * @return {Object} An object with from and to properties.
- */
-ImageEncoder.MetadataEncoder.prototype.
-    findInsertionRange = function(encodedImage) { return {from: 0, to: 0} };
-
-/**
- * Return serialized metadata ready to write to an image file.
- * The return type is optimized for passing to Blob.append.
- * @return {ArrayBuffer} // TODO(JSDOC).
- */
-ImageEncoder.MetadataEncoder.prototype.encode = function() {
-  return new Uint8Array(0).buffer;
-};