1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef CHROME_COMMON_THUMBNAIL_SCORE_H_ 6 #define CHROME_COMMON_THUMBNAIL_SCORE_H_ 7 8 #include <string> 9 #include "base/time/time.h" 10 11 // A set of metadata about a Thumbnail. 12 struct ThumbnailScore { 13 // Initializes the ThumbnailScore to the absolute worst possible values 14 // except for time, which is set to Now(), and redirect_hops_from_dest which 15 // is set to 0. 16 ThumbnailScore(); 17 18 // Builds a ThumbnailScore with the passed in values, and sets the 19 // thumbnail generation time to Now(). 20 ThumbnailScore(double score, bool clipping, bool top); 21 22 // Builds a ThumbnailScore with the passed in values. 23 ThumbnailScore(double score, bool clipping, bool top, 24 const base::Time& time); 25 ~ThumbnailScore(); 26 27 // Tests for equivalence between two ThumbnailScore objects. 28 bool Equals(const ThumbnailScore& rhs) const; 29 30 // Returns string representation of this object. 31 std::string ToString() const; 32 33 // How "boring" a thumbnail is. The boring score is the 0,1 ranged 34 // percentage of pixels that are the most common luma. Higher boring 35 // scores indicate that a higher percentage of a bitmap are all the 36 // same brightness (most likely the same color). 37 // 38 // The score should only be used for comparing two thumbnails taken from 39 // the same page to see which one is more boring/interesting. The 40 // absolute score is not suitable for judging whether the thumbnail is 41 // actually boring or not. For instance, www.google.com is very 42 // succinct, so the boring score can be as high as 0.9, depending on the 43 // browser window size. 44 double boring_score; 45 46 // Whether the thumbnail was taken with height greater than 47 // width or width greater than height and the aspect ratio less than 48 // kTooWideAspectRatio. In cases where we don't have |good_clipping|, 49 // the thumbnails are either clipped from the horizontal center of the 50 // window, or are otherwise weirdly stretched. 51 bool good_clipping; 52 53 // Whether this thumbnail was taken while the renderer was 54 // displaying the top of the page. Most pages are more recognizable 55 // by their headers then by a set of random text half way down the 56 // page; i.e. most MediaWiki sites would be indistinguishable by 57 // thumbnails with |at_top| set to false. 58 bool at_top; 59 60 // Whether this thumbnail was taken after load was completed. 61 // Thumbnails taken while page loading may only contain partial 62 // contents. 63 bool load_completed; 64 65 // Record the time when a thumbnail was taken. This is used to make 66 // sure thumbnails are kept fresh. 67 base::Time time_at_snapshot; 68 69 // The number of hops from the final destination page that this thumbnail was 70 // taken at. When a thumbnail is taken, this will always be the redirect 71 // destination (value of 0). 72 // 73 // For the most visited view, we'll sometimes get thumbnails for URLs in the 74 // middle of a redirect chain. In this case, the top sites component will set 75 // this value so the distance from the destination can be taken into account 76 // by the comparison function. 77 // 78 // If "http://google.com/" redirected to "http://www.google.com/", then 79 // a thumbnail for the first would have a redirect hop of 1, and the second 80 // would have a redirect hop of 0. 81 int redirect_hops_from_dest; 82 83 // How bad a thumbnail needs to be before we completely ignore it. 84 static const double kThumbnailMaximumBoringness; 85 86 // We consider a thumbnail interesting enough if the boring score is 87 // lower than this. 88 static const double kThumbnailInterestingEnoughBoringness; 89 90 // Time before we take a worse thumbnail (subject to 91 // kThumbnailMaximumBoringness) over what's currently in the database 92 // for freshness. 93 static const int64 kUpdateThumbnailTimeDays; 94 95 // Penalty of how much more boring a thumbnail should be per hour. 96 static const double kThumbnailDegradePerHour; 97 98 // If a thumbnail is taken with the aspect ratio greater than or equal to 99 // this value, |good_clipping| is to false. 100 static const double kTooWideAspectRatio; 101 102 // Checks whether we should consider updating a new thumbnail based on 103 // this score. For instance, we don't have to update a new thumbnail 104 // if the current thumbnail is new and interesting enough. 105 bool ShouldConsiderUpdating(); 106 }; 107 108 // Checks whether we should replace one thumbnail with another. 109 bool ShouldReplaceThumbnailWith(const ThumbnailScore& current, 110 const ThumbnailScore& replacement); 111 112 #endif // CHROME_COMMON_THUMBNAIL_SCORE_H_ 113
