Added new class gfx::ImageFamily.

ui/gfx/image/image_family.cc

+// Copyright 2013 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.
+
+#include "ui/gfx/image/image_family.h"
+
+#include <cmath>
+
+#include "ui/gfx/image/image.h"
+#include "ui/gfx/image/image_skia.h"
+#include "ui/gfx/size.h"
+
+namespace gfx {
+
+ImageFamily::ImageFamily() {}
+ImageFamily::~ImageFamily() {}
+
+void ImageFamily::Add(const gfx::Image& image) {
+  gfx::Size size = image.Size();
+  if (size.IsEmpty()) {
+    map_[MapKey(1.0f, 0)] = image;
+  } else {
+    float aspect = static_cast<float>(size.width()) / size.height();
+    DCHECK_GT(aspect, 0.0f);
+    map_[MapKey(aspect, size.width())] = image;
+  }
+}
+
+void ImageFamily::Add(const gfx::ImageSkia& image_skia) {
+  Add(gfx::Image(image_skia));
+}
+
+const gfx::Image* ImageFamily::Get(int width, int height) const {
+  if (map_.empty())
+    return NULL;
+
+  // If either width or height is 0, both are.
+  float desired_aspect;
+  if (height == 0 || width == 0) {
+    desired_aspect = 1.0f;
+    height = 0;
+    width = 0;
+  } else {
+    desired_aspect = static_cast<float>(width) / height;
+  }
+  DCHECK_GT(desired_aspect, 0.0f);
+
+  float closest_aspect = GetClosestAspect(desired_aspect);
+
+  // If thinner than desired, search for images with width such that the
+  // corresponding height is greater than or equal to the desired height.
+  int desired_width = closest_aspect <= desired_aspect ?
+      width : static_cast<int>(ceilf(height * closest_aspect));

[Robert Sesek, 2013/04/01 20:57:45]

Do you need this cast or can you just let it truncate (though that may cause a
warning)?

[Matt Giuca, 2013/04/02 06:11:28]

I explicitly want ceil because it will satisfy the property of finding an image
with height >= the desired height. If I use trunc/floor, it might find an image
with a height slightly smaller than the desired height.

+
+  // Get the best-sized image with the aspect ratio.
+  return GetWithExactAspect(closest_aspect, desired_width);
+}
+
+float ImageFamily::GetClosestAspect(float desired_aspect) const {
+  // Find the two aspect ratios on either side of desired_aspect.
+  std::map<MapKey, gfx::Image>::const_iterator greater_or_equal =
+      map_.lower_bound(MapKey(desired_aspect, 0.0f));
+  // Early exit optimization if there is an exact match.
+  if (greater_or_equal != map_.end() &&
+      greater_or_equal->first.aspect() == desired_aspect) {
+    return desired_aspect;
+  }
+
+  // No exact match; greater_or_equal will point to the first image with aspect
+  // ratio >= desired_aspect, and less_than will point to the last image with
+  // aspect ratio < desired_aspect.
+  if (greater_or_equal != map_.begin()) {
+    std::map<MapKey, gfx::Image>::const_iterator less_than =
+        greater_or_equal;
+    --less_than;
+    float thinner_aspect = less_than->first.aspect();
+    DCHECK_GT(thinner_aspect, 0.0f);
+    DCHECK_LT(thinner_aspect, desired_aspect);
+    if (greater_or_equal != map_.end()) {
+      float wider_aspect = greater_or_equal->first.aspect();
+      DCHECK_GT(wider_aspect, desired_aspect);
+      if ((wider_aspect / desired_aspect) < (desired_aspect / thinner_aspect))
+        return wider_aspect;
+    }
+    return thinner_aspect;
+  } else {
+    // No aspect ratio is less than or equal to desired_aspect.
+    DCHECK(greater_or_equal != map_.end());
+    float wider_aspect = greater_or_equal->first.aspect();
+    DCHECK_GT(wider_aspect, desired_aspect);
+    return wider_aspect;
+  }
+}
+
+const gfx::Image* ImageFamily::GetWithExactAspect(float aspect,
+                                                  int width) const {
+  // Find the two images of given aspect ratio on either side of width.
+  std::map<MapKey, gfx::Image>::const_iterator greater_or_equal =
+      map_.lower_bound(MapKey(aspect, width));
+  if (greater_or_equal != map_.end() &&
+      greater_or_equal->first.aspect() == aspect) {
+    // We have found the smallest image of the same size or greater.
+    return &greater_or_equal->second;
+  }
+
+  DCHECK(greater_or_equal != map_.begin());
+  std::map<MapKey, gfx::Image>::const_iterator less_than = greater_or_equal;
+  --less_than;
+  // This must be true because there must be at least one image with |aspect|.
+  DCHECK_EQ(less_than->first.aspect(), aspect);
+  // We have found the largest image smaller than desired.
+  return &less_than->second;
+}
+
+ImageFamily::const_iterator::const_iterator(
+    const std::map<MapKey, gfx::Image>::const_iterator& other)
+    : map_iterator_(other) {}
+
+}  // namespace gfx