chrome/browser/thumbnails/content_analysis.h

   1 // Copyright (c) 2013 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_BROWSER_THUMBNAILS_CONTENT_ANALYSIS_H_
   6 #define CHROME_BROWSER_THUMBNAILS_CONTENT_ANALYSIS_H_
   7
   8 #include <vector>
   9
  10 #include "base/basictypes.h"
  11 #include "third_party/skia/include/core/SkColor.h"
  12 #include "ui/gfx/geometry/rect.h"
  13 #include "ui/gfx/geometry/size.h"
  14
  15 class SkBitmap;
  16
  17 namespace thumbnailing_utils {
  18
  19 // Compute in-place gaussian gradient magnitude of |input_bitmap| with sigma
  20 // |kernel_sigma|. |input_bitmap| is requried to be of SkBitmap::kA8_Config
  21 // type. The routine computes first-order gaussian derivative on a
  22 // gaussian-smoothed image. Beware, this is fairly slow since kernel size is
  23 // 4 * kernel_sigma + 1.
  24 void ApplyGaussianGradientMagnitudeFilter(SkBitmap* input_bitmap,
  25                                           float kernel_sigma);
  26
  27 // Accumulates vertical and horizontal sum of pixel values from a subsection of
  28 // |input_bitmap| defined by |image_area|. The image is required to be of
  29 // SkBitmap::kA8_Config type.
  30 // If non-empty |target_size| is given, the routine will use it to process the
  31 // profiles with closing operator sized to eliminate gaps which would be smaller
  32 // than 1 pixel after rescaling to |target_size|.
  33 // If |apply_log| is true, logarithm of counts are used for morhology (and
  34 // returned).
  35 void ExtractImageProfileInformation(const SkBitmap& input_bitmap,
  36                                     const gfx::Rect& image_area,
  37                                     const gfx::Size& target_size,
  38                                     bool apply_log,
  39                                     std::vector<float>* rows,
  40                                     std::vector<float>* columns);
  41
  42 // Compute a threshold value separating background (low) from signal (high)
  43 // areas in the |input| profile.
  44 float AutoSegmentPeaks(const std::vector<float>& input);
  45
  46 // Compute and return a workable (not too distorted, not bigger than the image)
  47 // target size for retargeting in ConstrainedProfileSegmentation. |target_size|
  48 // is the desired image size (defines aspect ratio and minimal image size) while
  49 // |computed_size| is the size of a result of unconstrained segmentation.
  50 // This routine makes very little sense outside ConstrainedProfileSegmentation
  51 // and is exposed only for unit tests (it is somehow complicated).
  52 gfx::Size AdjustClippingSizeToAspectRatio(const gfx::Size& target_size,
  53                                           const gfx::Size& image_size,
  54                                           const gfx::Size& computed_size);
  55
  56 // Compute thresholding guides |included_rows| and |included_columns| by
  57 // segmenting 1-d profiles |row_profile| and |column_profile|. The routine will
  58 // attempt to keep the image which would result from using these guides as close
  59 // to the desired aspect ratio (given by |target_size|) as reasonable.
  60 void ConstrainedProfileSegmentation(const std::vector<float>& row_profile,
  61                                     const std::vector<float>& column_profile,
  62                                     const gfx::Size& target_size,
  63                                     std::vector<bool>* included_rows,
  64                                     std::vector<bool>* included_columns);
  65
  66 // Shrinks the source |bitmap| by removing rows and columns where |rows| and
  67 // |columns| are false, respectively. The function returns a new bitmap if the
  68 // shrinking can be performed and an empty instance otherwise.
  69 SkBitmap ComputeDecimatedImage(const SkBitmap& bitmap,
  70                                const std::vector<bool>& rows,
  71                                const std::vector<bool>& columns);
  72
  73 // Creates a new bitmap which contains only 'interesting' areas of
  74 // |source_bitmap|. The |target_size| is used to estimate some computation
  75 // parameters, but the resulting bitmap will not necessarily be of that size.
  76 // |kernel_sigma| defines the degree of image smoothing in gradient computation.
  77 // For a natural-sized (not shrunk) screenshot at 96 DPI and regular font size
  78 // 5.0 was determined to be a good value.
  79 SkBitmap CreateRetargetedThumbnailImage(const SkBitmap& source_bitmap,
  80                                         const gfx::Size& target_size,
  81                                         float kernel_sigma);
  82
  83 }  // namespace thumbnailing_utils
  84
  85 #endif  // CHROME_BROWSER_THUMBNAILS_CONTENT_ANALYSIS_H_