[filebrowser] More reliable file saving in Photo Editor

chrome/browser/resources/file_manager/js/image_parsers.js

+// Copyright (c) 2011 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.
+
+/* Base class for image metadata parsers that only need to look at a short
+  fragment at the start of the file */
+function SimpleImageParser(parent, type, urlFilter, headerSize) {
+  ImageParser.call(this, parent, type, urlFilter);
+  this.headerSize = headerSize;
+}
+
+SimpleImageParser.prototype = {__proto__: ImageParser.prototype};
+
+SimpleImageParser.prototype.parse = function(file, callback, errorCallback) {
+  var self = this;
+  util.readFileBytes(file, 0, this.headerSize,
+    function (file, br) {
+      try {
+        var metadata = self.createDefaultMetadata();
+        self.parseHeader(metadata, br);
+        callback(metadata);
+      } catch(e) {
+        errorCallback(e.toString());
+      }
+    },
+    errorCallback);
+};
+
+
+function PngParser(parent) {
+  SimpleImageParser.call(this, parent, 'png', /\.png$/i, 24);
+}
+
+PngParser.prototype = {__proto__: SimpleImageParser.prototype};
+
+PngParser.prototype.parseHeader = function(metadata, br) {
+  br.setByteOrder(ByteReader.BIG_ENDIAN);
+
+  var signature = br.readString(8);
+  if (signature != '\x89PNG\x0D\x0A\x1A\x0A')
+    throw new Error('Invalid PNG signature: ' + signature);
+
+  br.seek(12);
+  var ihdr = br.readString(4);
+  if (ihdr != 'IHDR')
+    throw new Error('Missing IHDR chunk');
+
+  metadata.width = br.readScalar(4);
+  metadata.height = br.readScalar(4);
+};
+
+MetadataDispatcher.registerParserClass(PngParser);
+
+
+function BmpParser(parent) {
+  SimpleImageParser.call(this, parent, 'bmp', /\.bmp$/i, 28);
+}
+
+BmpParser.prototype = {__proto__: SimpleImageParser.prototype};
+
+BmpParser.prototype.parseHeader = function(metadata, br) {
+  br.setByteOrder(ByteReader.LITTLE_ENDIAN);
+
+  var signature = br.readString(2);
+  if (signature != 'BM')
+    throw new Error('Invalid BMP signature: ' + signature);
+
+  br.seek(18);
+  metadata.width = br.readScalar(4);
+  metadata.height = br.readScalar(4);
+};
+
+MetadataDispatcher.registerParserClass(BmpParser);
+
+
+function GifParser(parent) {
+  SimpleImageParser.call(this, parent, 'gif', /\.Gif$/i, 10);
+}
+
+GifParser.prototype = {__proto__: SimpleImageParser.prototype};
+
+GifParser.prototype.parseHeader = function(metadata, br) {
+  br.setByteOrder(ByteReader.LITTLE_ENDIAN);
+
+  var signature = br.readString(6);
+  if (!signature.match(/GIF8(7|9)a/))
+    throw new Error('Invalid GIF signature: ' + signature);
+
+  metadata.width = br.readScalar(2);
+  metadata.height = br.readScalar(2);
+};
+
+MetadataDispatcher.registerParserClass(GifParser);