LayoutTests/fast/canvas/canvas-imageSmoothingEnabled_t01.dart

/*
 * Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 * for details. All rights reserved. Use of this source code is governed by a
 * BSD-style license that can be found in the LICENSE file.
 */
/** 
 * @description Tests for the imageSmoothingEnabled attribute.
 */
import "dart:html";
import "../../testcommon.dart";
import "../../../Utils/async_utils.dart";

main() {
  var ctx = createContext2d("canvas");

  debug("Test that the default value is true.");
  shouldBe(ctx.imageSmoothingEnabled, true);

  debug("Test that false is returned after a the attribute is set to false.");
  ctx.imageSmoothingEnabled = false;
  shouldBe(ctx.imageSmoothingEnabled, false);

  debug("Test that restore works. We save a false state; create, then save a true state; and then finally restore.");
  ctx.save();
  ctx.imageSmoothingEnabled = true;
  ctx.restore();
  shouldBe(ctx.imageSmoothingEnabled, false);

  var image = document.createElement('canvas');
  image.width = 2;
  image.height = 1;

  // We use this to colour the individual pixels
  var dotter = ctx.createImageData(1, 1);

  // Colour the left pixel black.
  dotter.data[0] = 0;
  dotter.data[1] = 0;
  dotter.data[2] = 0;
  dotter.data[3] = 255;
  image.getContext('2d').putImageData(dotter, 0, 0);

  // Colour the right pixel white.
  dotter.data[0] = 255;
  dotter.data[1] = 255;
  dotter.data[2] = 255;
  dotter.data[3] = 255;
  image.getContext('2d').putImageData(dotter, 1, 0);


  debug("New canvas element created.");
  var canvas = document.createElement('canvas');
  canvas.width = 4;
  canvas.height = 1;
  ctx = canvas.getContext('2d');
  ctx.drawImageScaled(image, 0, 0, canvas.width, canvas.height);
  var left_of_center_pixel = ctx.getImageData(1, 0, 1, 1);

  debug("Test that the image is smoothed by default. We check by making sure the pixel just to the left of the middle line is not completely black.");
  shouldBe(left_of_center_pixel.data[0] != 0, true);
  shouldBe(left_of_center_pixel.data[1] != 0, true);
  shouldBe(left_of_center_pixel.data[2] != 0, true);

  ctx.imageSmoothingEnabled = false;
  ctx.drawImageScaled(image, 0, 0, canvas.width, canvas.height);
  left_of_center_pixel = ctx.getImageData(1, 0, 1, 1);
  debug("Test that nearest neighbour is used when imageSmoothingEnabled is set to false. We check this by making sure the pixel just to the left of the middle line is completely black.");
  shouldBe(left_of_center_pixel.data[0], 0);
  shouldBe(left_of_center_pixel.data[1], 0);
  shouldBe(left_of_center_pixel.data[2], 0);

  ctx.imageSmoothingEnabled = true;
  ctx.drawImageScaled(image, 0, 0, canvas.width, canvas.height);
  left_of_center_pixel = ctx.getImageData(1, 0, 1, 1);
  debug("Test that the image is smoothed when imageSmoothingEnabled is set to true.");
  shouldBe(left_of_center_pixel.data[0] != 0, true);
  shouldBe(left_of_center_pixel.data[1] != 0, true);
  shouldBe(left_of_center_pixel.data[2] != 0, true);

  debug("Test that restoring actually changes smoothing and not just the attribute value. We are restoring to a point where imageSmoothingEnabled is set to false.");
  ctx.imageSmoothingEnabled = false;
  ctx.save();
  ctx.imageSmoothingEnabled = true;
  ctx.restore();
  ctx.drawImageScaled(image, 0, 0, canvas.width, canvas.height);
  left_of_center_pixel = ctx.getImageData(1, 0, 1, 1);
  shouldBe(left_of_center_pixel.data[0], 0);
  shouldBe(left_of_center_pixel.data[1], 0);
  shouldBe(left_of_center_pixel.data[2], 0);
}