Pre-scaling images to speed up feedback in Image Editor.

chrome/browser/resources/file_manager/js/image_editor/viewport.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.
+
+/**
+ * Viewport class controls the way the image is displayed (scale, offset etc).
+ */
+function Viewport(repaintCallback) {
+  this.repaintCallback_ = repaintCallback;
+
+  this.imageBounds_ = new Rect();
+  this.screenBounds_ = new Rect();
+
+  this.scale_ = 1;
+  this.offsetX_ = 0;
+  this.offsetY_ = 0;
+
+  this.generation_ = 0;
+
+  this.scaleControl_ = null;
+
+  this.update();
+}
+
+/*
+ * Viewport modification.
+ */
+
+Viewport.prototype.setScaleControl = function(scaleControl) {
+  this.scaleControl_ = scaleControl;
+};
+
+Viewport.prototype.setImageSize = function(width, height) {
+  this.imageBounds_ = new Rect(width, height);
+  if (this.scaleControl_) this.scaleControl_.displayImageSize(width, height);
+  this.invalidateCaches();
+};
+
+Viewport.prototype.setScreenSize = function(width, height) {
+  this.screenBounds_ = new Rect(width, height);
+  if (this.scaleControl_)
+    this.scaleControl_.setMinScale(this.getFittingScale());
+  this.invalidateCaches();
+};
+
+Viewport.prototype.getScale = function() { return this.scale_ };
+
+Viewport.prototype.setScale = function(scale, notify) {
+  if (this.scale_ == scale) return;
+  this.scale_ = scale;
+  if (notify && this.scaleControl_) this.scaleControl_.displayScale(scale);
+  this.invalidateCaches();
+};
+
+Viewport.prototype.getFittingScale = function() {
+  var scaleX = this.screenBounds_.width / this.imageBounds_.width;
+  var scaleY = this.screenBounds_.height / this.imageBounds_.height;
+  return Math.min(scaleX, scaleY) * 0.85;
+};
+
+Viewport.prototype.fitImage = function() {
+  var scale = this.getFittingScale();
+  if (this.scaleControl_) this.scaleControl_.setMinScale(scale);
+  this.setScale(scale, true);
+};
+
+Viewport.prototype.getOffsetX = function () { return this.offsetX_ };
+
+Viewport.prototype.getOffsetY = function () { return this.offsetY_ };
+
+Viewport.prototype.setOffset = function(x, y, ignoreClipping) {
+  if (!ignoreClipping) {
+    x = this.clampOffsetX_(x);
+    y = this.clampOffsetY_(y);
+  }
+  if (this.offsetX_ == x && this.offsetY_ == y) return;
+  this.offsetX_ = x;
+  this.offsetY_ = y;
+  this.invalidateCaches();
+};
+
+Viewport.prototype.setCenter = function(x, y, ignoreClipping) {
+  this.setOffset(
+      this.imageBounds_.width / 2 - x,
+      this.imageBounds_.height / 2 - y,
+      ignoreClipping);
+};
+
+/**
+ * Return a closure that can be called to pan the image.
+ * Useful for implementing non-trivial variants of panning (overview etc).
+ * @param {Number} originalX The x coordinate on the screen canvas that
+ *                 corresponds to zero change to offsetX.
+ * @param {Number} originalY The y coordinate on the screen canvas that
+ *                 corresponds to zero change to offsetY.
+ * @param {Function} scaleFunc returns the current image to screen scale.
+ * @param {Function} hitFunc returns true if (x,y) is in the valid region.
+ */
+Viewport.prototype.createOffsetSetter = function (
+    originalX, originalY, scaleFunc, hitFunc) {
+  var originalOffsetX = this.offsetX_;
+  var originalOffsetY = this.offsetY_;
+  if (!hitFunc) hitFunc = function() { return true };
+  if (!scaleFunc) scaleFunc = this.getScale.bind(this);
+
+  var self = this;
+  return function(x, y) {
+    if (hitFunc(x, y)) {
+      var scale = scaleFunc();
+      self.setOffset(
+          originalOffsetX + (x - originalX) / scale,
+          originalOffsetY + (y - originalY) / scale);
+      self.repaint();
+    }
+  };
+};
+
+/*
+ * Access to the current viewport state.
+ */
+
+/**
+ * @return {Rect} The image bounds in image coordinates.
+ */
+Viewport.prototype.getImageBounds = function() { return this.imageBounds_ };
+
+/**
+* @return {Rect} The screen bounds in screen coordinates.
+*/
+Viewport.prototype.getScreenBounds = function() { return this.screenBounds_ };
+
+/**
+ * @return {Rect} The visible part of the image, in image coordinates.
+ */
+Viewport.prototype.getImageClipped = function() { return this.imageClipped_ };
+
+/**
+ * @return {Rect} The visible part of the image, in screen coordinates.
+ */
+Viewport.prototype.getScreenClipped = function() { return this.screenClipped_ };
+
+/**
+ * A counter that is incremented with each viewport state change.
+ * Clients that cache anything that depends on the viewport state should keep
+ * track of this counter.
+ */
+Viewport.prototype.getCacheGeneration = function() { return this.generation_ };
+
+/**
+ * Called on evert view port state change (even if repaint has not been called).
+ */
+Viewport.prototype.invalidateCaches = function() { this.generation_++ };
+
+/**
+ * @return {Rect} The image bounds in screen coordinates.
+ */
+Viewport.prototype.getImageBoundsOnScreen = function() {
+  return this.imageOnScreen_;
+};
+
+/*
+ * Conversion between the screen and image coordinate spaces.
+ */
+
+Viewport.prototype.screenToImageSize = function(size) {
+  return size / this.getScale();
+};
+
+Viewport.prototype.screenToImageX = function(x) {
+  return Math.round((x - this.imageOnScreen_.left) / this.getScale());
+};
+
+Viewport.prototype.screenToImageY = function(y) {
+  return Math.round((y - this.imageOnScreen_.top) / this.getScale());
+};
+
+Viewport.prototype.screenToImageRect = function(rect) {
+  return new Rect(
+      this.screenToImageX(rect.left),
+      this.screenToImageY(rect.top),
+      this.screenToImageSize(rect.width),
+      this.screenToImageSize(rect.height));
+};
+
+Viewport.prototype.imageToScreenSize = function(size) {
+  return size * this.getScale();
+};
+
+Viewport.prototype.imageToScreenX = function(x) {
+  return Math.round(this.imageOnScreen_.left + x * this.getScale());
+};
+
+Viewport.prototype.imageToScreenY = function(y) {
+  return Math.round(this.imageOnScreen_.top + y * this.getScale());
+};
+
+Viewport.prototype.imageToScreenRect = function(rect) {
+  return new Rect(
+      this.imageToScreenX(rect.left),
+      this.imageToScreenY(rect.top),
+      this.imageToScreenSize(rect.width),
+      this.imageToScreenSize(rect.height));
+};
+
+/**
+ * @return {Boolean} True if some part of the image is clipped by the screen.
+ */
+Viewport.prototype.isClipped = function () {
+  return this.getMarginX_() < 0 || this.getMarginY_() < 0;
+};
+
+/**
+ * Horizontal margin. Negative if the image is clipped horizontally.
+ */
+Viewport.prototype.getMarginX_ = function() {
+  return Math.floor(
+    (this.screenBounds_.width  - this.imageBounds_.width * this.scale_) / 2);
+};
+
+/**
+ * Vertical margin. Negative if the image is clipped vertically.
+ */
+Viewport.prototype.getMarginY_ = function() {
+  return Math.floor(
+    (this.screenBounds_.height - this.imageBounds_.height * this.scale_) / 2);
+};
+
+Viewport.prototype.clampOffsetX_ = function(x) {
+  var limit = Math.max(0, -this.getMarginX_() / this.getScale());
+  return ImageUtil.clamp(-limit, x, limit);
+};
+
+Viewport.prototype.clampOffsetY_ = function(y) {
+  var limit = Math.max(0, -this.getMarginY_() / this.getScale());
+  return ImageUtil.clamp(-limit, y, limit);
+};
+
+/**
+ * Recalculate the viewport parameters.
+ */
+Viewport.prototype.update = function() {
+  var scale = this.getScale();
+
+  // Image bounds in screen coordinates.
+  this.imageOnScreen_ = new Rect(
+      this.getMarginX_(),
+      this.getMarginY_(),
+      Math.floor(this.imageBounds_.width * scale),
+      Math.floor(this.imageBounds_.height * scale));
+
+  // A visible part of the image in image coordinates.
+  this.imageClipped_ = new Rect(this.imageBounds_);
+
+  // A visible part of the image in screen coordinates.
+  this.screenClipped_ = new Rect(this.screenBounds_);
+
+  // Adjust for the offset.
+  if (this.imageOnScreen_.left < 0) {
+    this.imageOnScreen_.left += this.clampOffsetX_(this.offsetX_) * scale;
+    this.imageClipped_.left = -this.imageOnScreen_.left / scale;
+    this.imageClipped_.width = this.screenBounds_.width / scale;
+  } else {
+    this.screenClipped_.left = this.imageOnScreen_.left;
+    this.screenClipped_.width = this.imageOnScreen_.width;
+  }
+
+  if (this.imageOnScreen_.top < 0) {
+    this.imageOnScreen_.top += this.clampOffsetY_(this.offsetY_) * scale;
+    this.imageClipped_.top = -this.imageOnScreen_.top / scale;
+    this.imageClipped_.height = this.screenBounds_.height / scale;
+  } else {
+    this.screenClipped_.top = this.imageOnScreen_.top;
+    this.screenClipped_.height = this.imageOnScreen_.height;
+  }
+};
+
+Viewport.prototype.repaint = function () {
+  if (this.repaintCallback_) this.repaintCallback_();
+};