Add ImageOrientation class.

ui/file_manager/file_manager/foreground/js/metadata/image_orientation.js

Index: ui/file_manager/file_manager/foreground/js/metadata/image_orientation.js
diff --git a/ui/file_manager/file_manager/foreground/js/metadata/image_orientation.js b/ui/file_manager/file_manager/foreground/js/metadata/image_orientation.js
new file mode 100644
index 0000000000000000000000000000000000000000..ba9bba146f26dacf30846c51cf6479a839fd6315
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+++ b/ui/file_manager/file_manager/foreground/js/metadata/image_orientation.js
@@ -0,0 +1,126 @@
+// Copyright 2015 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.
+
+/**
+ * Class representing image orientation.
+ * The constructor takes 2x2 matrix value that cancels the image orientation:
+ * |a, c|
+ * |b, d|
+ * @param {number} a
+ * @param {number} b
+ * @param {number} c
+ * @param {number} d
+ * @struct
+ * @constructor
+ */
+function ImageOrientation(a, b, c, d) {
+  /**
+   * @public {number}
+   * @const
+   */
+  this.a = a;
+
+  /**
+   * @public {number}
+   * @const
+   */
+  this.b = b;
+
+  /**
+   * @public {number}
+   * @const
+   */
+  this.c = c;
+
+  /**
+   * @public {number}
+   * @const
+   */
+  this.d = d;
+}
+
+/**
+ * @param {number} orientation 1-based orientation number defined by EXIF.
+ * @return {!ImageOrientation}
+ */
+ImageOrientation.fromExifOrientation = function(orientation) {
+  switch (~~orientation) {
+    case 1:
+      return new ImageOrientation(1, 0, 0, 1);
+    case 2:
+      return new ImageOrientation(-1, 0, 0, 1);
+    case 3:
+      return new ImageOrientation(-1, 0, 0, -1);
+    case 4:
+      return new ImageOrientation(1, 0, 0, -1);
+    case 5:
+      return new ImageOrientation(0, 1, 1, 0);
+    case 6:
+      return new ImageOrientation(0, 1, -1, 0);
+    case 7:
+      return new ImageOrientation(0, -1, -1, 0);
+    case 8:
+      return new ImageOrientation(0, -1, 1, 0);
+    default:
+      console.error('Invalid orientation number.');
+      return new ImageOrientation(1, 0, 0, 1);
+  }
+};
+
+/**
+ * @param {number} rotation90 Clockwise degrees / 90.
+ * @return {!ImageOrientation}
+ */
+ImageOrientation.fromDriveOrientation = function(rotation90) {
+  switch (~~(rotation90 % 4)) {
+    case 0:
+      return new ImageOrientation(1, 0, 0, 1);
+    case 1:
+      return new ImageOrientation(0, -1, 1, 0);
+    case 2:
+      return new ImageOrientation(-1, 0, 0, -1);
+    case 3:
+      return new ImageOrientation(0, 1, -1, 0);
+    default:
+      console.error('Invalid orientation number.');
+      return new ImageOrientation(1, 0, 0, 1);
+  }
+};
+
+/**
+ * Obtains the image size after cancelling its orientation.
+ * @param {number} imageWidth
+ * @param {number} imageHeight
+ * @return {{width:number, height:number}}
+ */
+ImageOrientation.prototype.getSizeAfterCancelling = function(
+    imageWidth, imageHeight) {
+  var projectedX = this.a * imageWidth + this.c * imageHeight;
+  var projectedY = this.b * imageWidth + this.d * imageHeight;
+  return {
+    width: Math.abs(projectedX),
+    height: Math.abs(projectedY)
+  };
+};
+
+/**
+ * Applies the transformation that cancels the image orientation to the given
+ * context.
+ * @param {!CanvasRenderingContext2D} context
+ * @param {number} imageWidth
+ * @param {number} imageHeight
+ */
+ImageOrientation.prototype.cancelImageOrientation = function(
+    context, imageWidth, imageHeight) {
+  // Calculate where to project the point of (imageWidth, imageHeight).
+  var projectedX = this.a * imageWidth + this.c * imageHeight;
+  var projectedY = this.b * imageWidth + this.d * imageHeight;
+
+  // If the projected point coordinates are negative, add offset to cancel it.
+  var offsetX = projectedX < 0 ? -projectedX : 0;
+  var offsetY = projectedY < 0 ? -projectedY : 0;
+
+  // Apply the transform.
+  context.setTransform(this.a, this.b, this.c, this.d, offsetX, offsetY);
+};