Add magnifying ability, perceptual diff and improve layout of Skia Tryserver HTML output

compute_engine_scripts/telemetry/static-files/diff_viewer.js

+var MAX_SWAP_IMG_SIZE = 400;

[epoger, 2014/02/03 21:17:13]

Do we need copyright notice up here?

+var MAGNIFIER_WIDTH = 200;
+var MAGNIFIER_HEIGHT = 200;

[epoger, 2014/02/03 21:17:13]

So, if we are hosting this file within Google Storage, what is the HTTP-cacheing
update policy?  (In other words, is there some lag between when we update the
file and when that update will become available to clients?)

If there is non-negligible delay, and we envision ever making changes to this
file, we may need to store it using a version number to prevent code version
mismatches.

+var MAGNIFIER_HALF_WIDTH = MAGNIFIER_WIDTH * 0.5;
+var MAGNIFIER_HALF_HEIGHT = MAGNIFIER_HEIGHT * 0.5;
+var MAGNIFIER_SCALE_FACTOR = 2.0;
+
+angular.module('diff_viewer', []).directive('imgCompare', function() {
+  // Custom directive for comparing (3-way) images

[epoger, 2014/02/03 21:17:13]

Maybe it's just me, but this all seems like magic and I don't know how it gets
"plugged into" the rest of the UI.  Perhaps more documentation would be useful.

+  return {
+      restrict: 'E', // The directive can be used as an element name
+      replace: true, // The directive replaces itself with the template
+      template: '<canvas/>',
+      scope: true,
+      link: function(scope, elm, attrs, ctrl) {
+          var image = new Image();
+          var canvas = elm[0];
+          var ctx = canvas.getContext('2d');
+
+          var magnifyContent = false;
+          var maskCanvas = false;
+
+          // When the type attribute changes, load the image and then render
+          attrs.$observe('type', function(value) {
+              switch(value) {
+                case "differingPixelsInWhite":
+                    image.src = attrs.src;
+                    // maskCanvas = true;

[epoger, 2014/02/03 21:17:13]

why is this commented out?

+                    magnifyContent = true;
+                    break;
+                case "differencePerPixel":
+                    image.src = attrs.src;
+                    maskCanvas = true;
+                    break;
+                case "baseline":
+                    image.src = attrs.src;
+                    magnifyContent = true;
+                    break;
+                case "test":
+                    image.src = attrs.src;
+                    magnifyContent = true;
+                    break;
+                default:
+                    console.log("Unknown type attribute on <img-compare>: " + value);
+                    return;
+              }
+
+              image.onload = function() {
+                  // compute the scaled image width/height for image and canvas
+                  var divisor = 1;
+                  // Make it so the maximum size of an image is MAX_SWAP_IMG_SIZE,
+                  // and the images are scaled down in halves.
+                  while ((image.width / divisor) > MAX_SWAP_IMG_SIZE) {
+                      divisor *= 2;
+                  }
+
+                  scope.setImgScaleFactor(1 / divisor);

[epoger, 2014/02/03 21:17:13]

I don't know how JavaScript handles floating point math... might there be a
compelling reason to store the scale factor as its (integer) divisor component,
rather than as 1/divisor?

This might affect the results of multiplying by imgScaleFactor below...

+
+                  // Set canvas to correct size
+                  canvas.width = image.width * scope.imgScaleFactor;
+                  canvas.height = image.height * scope.imgScaleFactor;
+
+                  // update the size for non-alphaMask canvas when loading baseline image
+                  if (!scope.maskSizeUpdated) {
+                      if (!maskCanvas) {
+                          scope.updateMaskCanvasSize({width: canvas.width, height: canvas.height});
+                      }
+                      scope.maskCanvasSizeUpdated(true);
+                  }
+
+                  // render the image onto the canvas
+                  scope.renderImage();
+              }
+          });
+
+          // when updatedMaskSize changes, update mask canvas size.

[epoger, 2014/02/03 21:17:13]

Somewhere there needs to be an explanation of what the different mask sizes mean
in here.  (See also my comments at the bottom of this file.)

+          scope.$watch('updatedMaskSize', function(updatedSize) {
+              if (!maskCanvas) {
+                  return;
+              }
+
+              // rmistry: Commented out because was throwing js errors.

[epoger, 2014/02/03 21:17:13]

So, does this function do anything now?

+              // canvas.width = updatedSize.width;
+              // canvas.height = updatedSize.height;
+          });
+
+          // When the magnify attribute changes, render the magnified rect at
+          // the default zoom level.
+          scope.$watch('magnifyCenter', function(magCenter) {
+              if (!magnifyContent) {
+                  return;
+              }
+
+              scope.renderImage();
+
+              if (!magCenter) {
+                  return;
+              }
+
+              var magX = magCenter.x - MAGNIFIER_HALF_WIDTH;
+              var magY = magCenter.y - MAGNIFIER_HALF_HEIGHT;
+
+              var magMaxX = canvas.width - MAGNIFIER_WIDTH;
+              var magMaxY = canvas.height - MAGNIFIER_HEIGHT;
+
+              var magRect = { x: Math.max(0, Math.min(magX, magMaxX)),
+                              y: Math.max(0, Math.min(magY, magMaxY)),
+                              width: MAGNIFIER_WIDTH,
+                              height: MAGNIFIER_HEIGHT
+                            };
+
+              var imgRect = { x: (magCenter.x / scope.imgScaleFactor) - MAGNIFIER_HALF_WIDTH,
+                              y: (magCenter.y  / scope.imgScaleFactor) - MAGNIFIER_HALF_HEIGHT,
+                              width: MAGNIFIER_WIDTH,
+                              height: MAGNIFIER_HEIGHT
+                            };
+
+              // draw the magnified image
+              ctx.clearRect(magRect.x, magRect.y, magRect.width, magRect.height);
+              ctx.drawImage(image, imgRect.x, imgRect.y, imgRect.width, imgRect.height,
+                            magRect.x, magRect.y, magRect.width, magRect.height);
+
+              // draw the outline rect
+              ctx.beginPath();
+              ctx.rect(magRect.x, magRect.y, magRect.width, magRect.height);
+              ctx.lineWidth = 2;
+              ctx.strokeStyle = 'red';
+              ctx.stroke();
+
+          });
+
+          // render the image to the canvas. This is often done every frame prior
+          // to any special effects (i.e. magnification).
+          scope.renderImage = function() {
+            ctx.clearRect(0, 0, canvas.width, canvas.height);
+            ctx.drawImage(image, 0, 0, canvas.width, canvas.height);
+          };
+
+          // compute a rect (x,y,width,height) that represents the bounding box for
+          // the magnification effect
+          scope.computeMagnifierOutline = function(event) {
+            var scaledWidth = MAGNIFIER_WIDTH * scope.imgScaleFactor;
+            var scaledHeight = MAGNIFIER_HEIGHT * scope.imgScaleFactor;
+            return {
+              x: event.offsetX - (scaledWidth * 0.5),
+              y: event.offsetY  - (scaledHeight * 0.5),
+              width: scaledWidth,
+              height: scaledHeight
+            };
+          };
+
+          // event handler for mouse events that triggers the magnification
+          // effect across the 4 images being compared.
+          scope.MagnifyDraw = function(event, startMagnify) {
+              if (startMagnify) {

[epoger, 2014/02/03 21:17:13]

seems like indent levels shift freely between 2 and 4 within this file...

+                  scope.setMagnifierState(true);
+              }  else if (!scope.magnifierOn) {
+                  return;
+              }
+
+              scope.renderImage();
+
+              // render the magnifier outline rect
+              var rect = scope.computeMagnifierOutline(event);
+              ctx.save();
+              ctx.beginPath();
+              ctx.rect(rect.x, rect.y, rect.width, rect.height);
+              ctx.lineWidth = 2;
+              ctx.strokeStyle = 'red';
+              ctx.stroke();
+              ctx.restore();
+
+              // update scope on baseline / test that will cause them to render
+              scope.setMagnifyCenter({x: event.offsetX, y: event.offsetY});
+          };
+
+          // event handler that triggers the end of the magnification effect and
+          // resets all the canvases to their original state.
+          scope.MagnifyEnd = function(event) {
+              scope.renderImage();
+              // update scope on baseline / test that will cause them to render
+              scope.setMagnifierState(false);
+              scope.setMagnifyCenter(undefined);
+          };
+      }
+  };
+});
+
+function ImageController($scope, $http, $location, $timeout, $parse) {
+  $scope.imgScaleFactor = 1.0;
+  $scope.magnifierOn = false;
+  $scope.magnifyCenter = undefined;
+  $scope.updatedMaskSize = undefined;
+  $scope.maskSizeUpdated = false;
+
+  $scope.setImgScaleFactor = function(scaleFactor) {
+    $scope.imgScaleFactor = scaleFactor;
+  }
+
+  $scope.setMagnifierState = function(magnifierOn) {
+    $scope.magnifierOn = magnifierOn;
+  }
+
+  $scope.setMagnifyCenter = function(magnifyCenter) {
+      $scope.magnifyCenter = magnifyCenter;
+  }
+
+  $scope.updateMaskCanvasSize = function(updatedSize) {

[epoger, 2014/02/03 21:17:13]

Is there some reason we don't use consistent naming for this one, like so?

$scope.setMaskCanvasSize = function(maskCanvasSize) {
    $scope.maskCanvasSize = maskCanvasSize;
}

+      $scope.updatedMaskSize = updatedSize;
+  }
+
+  $scope.maskCanvasSizeUpdated = function(flag) {

[epoger, 2014/02/03 21:17:13]

What is this function for?  How does it relate to the function above it?

+      $scope.maskSizeUpdated = flag;
+  }
+}