Display images in multiline Braille

chrome/browser/resources/chromeos/chromevox/braille/braille_display_manager.js

 // Copyright 2014 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.
 
 /**
  * @fileoverview Puts text on a braille display.
  *
  */
 
 goog.provide('cvox.BrailleDisplayManager');
@@ skipping 101 matching lines @@
  *     of the display content is expanded when translating to braille.
  *     (See {@code cvox.ExpandingBrailleTranslator}).
  */
 cvox.BrailleDisplayManager.prototype.setContent = function(
     content, expansionType) {
   this.translateContent_(content, expansionType);
 };
 
 
 /**
+ * Takes an image, in the form of a data url, and displays it in braille
+ * onto the physical braille display and the virtual braille captions display.
+ * @param {!string} imageUrl The image, in the form of a data url.
+ */
+cvox.BrailleDisplayManager.prototype.setImageContent = function(imageUrl) {
+  if (!this.displayState_.available) {
+    return;
+  }
+
+  var rows = this.displayState_.textRowCount;
+  var columns = this.displayState_.textColumnCount;
+  var imageDataUrl = imageUrl;
+  var imgElement = document.createElement('img');
+  imgElement.src = imageDataUrl;
+  var canvas1 = document.createElement('canvas');

[dmazzoni, 2016/12/06 07:39:42]

Nit: maybe just |canvas| since you don't have more than one of the anymore

[ultimatedbz, 2016/12/07 22:03:48]

Done.

+  var context = canvas1.getContext('2d');
+  canvas1.width = columns * 2;
+  canvas1.height = rows * 4;
+  context.drawImage(imgElement, 0, 0, canvas1.width, canvas1.height);
+  var imageData = context.getImageData(0, 0, canvas1.width, canvas1.height);
+  var data = imageData.data;
+  var outputData = [];
+
+  // Convert image to black and white.
+  for (var i = 0; i < data.length; i += 4) {
+    // Show if the alpha value is visible (above 20) and the pixel is not
+    // white (under 600).
+    var show = (data[i] +
+                data[i + 1] +
+                data[i + 2] <= 200 * 3) &&
+                (data[i + 3]) >= 20;
+    outputData.push(show);
+  }
+
+  // Convert to Braille.
+  var buf = new ArrayBuffer(rows * columns);
+  var view = new Uint8Array(buf);
+  var coordsToBrailleDot = [0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80];
+  for (var i = 0; i < rows; i++) {
+    for (var j = 0; j < columns; j++) {
+      //Index in braille array
+      var index = i * columns + j;
+      view[index] = 0;
+      for (var x = 0; x < 2; x++) {
+        for (var y = 0; y < 4; y++) {
+          if (outputData[((i * columns * 4 + j + y * columns) * 2 + x)] == 1)
+            view[index] += coordsToBrailleDot[x * 4 + y];
+        }
+      }
+    }
+  }
+
+  if (this.realDisplayState_.available) {
+    chrome.brailleDisplayPrivate.writeDots(buf, buf.byteLength, 1);
+  }
+  if (cvox.BrailleCaptionsBackground.isEnabled()) {
+    cvox.BrailleCaptionsBackground.setImageContent(buf, rows, columns);
+  }
+};
+
+
+/**
  * Sets the command listener.  When a command is invoked, the listener will be
  * called with the BrailleKeyEvent corresponding to the command and the content
  * that was present on the display when the command was invoked.  The content
  * is guaranteed to be identical to an object previously used as the parameter
  * to cvox.BrailleDisplayManager.setContent, or null if no content was set.
  * @param {function(!cvox.BrailleKeyEvent, !cvox.NavBraille)} func The listener.
  */
 cvox.BrailleDisplayManager.prototype.setCommandListener = function(func) {
   this.commandListener_ = func;
 };
@@ skipping 230 matching lines @@
 };
 
 /**
  * @param {boolean} wordWrap
  * @private
  */
 cvox.BrailleDisplayManager.prototype.updatePanStrategy_ = function(wordWrap) {
   this.panStrategy_.setPanStrategy(wordWrap);
   this.refresh_();
 };