license.bot | f003cfe | 2008-08-24 09:55:55 +0900 | [diff] [blame^] | 1 | // Copyright (c) 2006-2008 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. |
initial.commit | 3f4a732 | 2008-07-27 06:49:38 +0900 | [diff] [blame] | 4 | |
| 5 | #ifndef BASE_GFX_CONVOLVER_H__ |
| 6 | #define BASE_GFX_CONVOLVER_H__ |
| 7 | |
| 8 | #include <vector> |
| 9 | |
| 10 | #include "base/basictypes.h" |
| 11 | |
awalker@google.com | a6edc1d | 2008-08-21 04:34:30 +0900 | [diff] [blame] | 12 | // avoid confusion with Mac OS X's math library (Carbon) |
| 13 | #if defined(OS_MACOSX) |
| 14 | #undef FloatToFixed |
| 15 | #endif |
| 16 | |
initial.commit | 3f4a732 | 2008-07-27 06:49:38 +0900 | [diff] [blame] | 17 | namespace gfx { |
| 18 | |
| 19 | // Represents a filter in one dimension. Each output pixel has one entry in this |
| 20 | // object for the filter values contributing to it. You build up the filter |
| 21 | // list by calling AddFilter for each output pixel (in order). |
| 22 | // |
| 23 | // We do 2-dimensional convolusion by first convolving each row by one |
| 24 | // ConvolusionFilter1D, then convolving each column by another one. |
| 25 | // |
| 26 | // Entries are stored in fixed point, shifted left by kShiftBits. |
| 27 | class ConvolusionFilter1D { |
| 28 | public: |
| 29 | // The number of bits that fixed point values are shifted by. |
| 30 | enum { kShiftBits = 14 }; |
| 31 | |
| 32 | ConvolusionFilter1D() : max_filter_(0) { |
| 33 | } |
| 34 | |
| 35 | // Convert between floating point and our fixed point representation. |
| 36 | static inline int16 FloatToFixed(float f) { |
| 37 | return static_cast<int16>(f * (1 << kShiftBits)); |
| 38 | } |
| 39 | static inline unsigned char FixedToChar(int16 x) { |
| 40 | return static_cast<unsigned char>(x >> kShiftBits); |
| 41 | } |
| 42 | |
| 43 | // Returns the maximum pixel span of a filter. |
| 44 | int max_filter() const { return max_filter_; } |
| 45 | |
| 46 | // Returns the number of filters in this filter. This is the dimension of the |
| 47 | // output image. |
| 48 | int num_values() const { return static_cast<int>(filters_.size()); } |
| 49 | |
| 50 | // Appends the given list of scaling values for generating a given output |
| 51 | // pixel. |filter_offset| is the distance from the edge of the image to where |
| 52 | // the scaling factors start. The scaling factors apply to the source pixels |
| 53 | // starting from this position, and going for the next |filter_length| pixels. |
| 54 | // |
| 55 | // You will probably want to make sure your input is normalized (that is, |
| 56 | // all entries in |filter_values| sub to one) to prevent affecting the overall |
| 57 | // brighness of the image. |
| 58 | // |
| 59 | // The filter_length must be > 0. |
| 60 | // |
| 61 | // This version will automatically convert your input to fixed point. |
| 62 | void AddFilter(int filter_offset, |
| 63 | const float* filter_values, |
| 64 | int filter_length); |
| 65 | |
| 66 | // Same as the above version, but the input is already fixed point. |
| 67 | void AddFilter(int filter_offset, |
| 68 | const int16* filter_values, |
| 69 | int filter_length); |
| 70 | |
| 71 | // Retrieves a filter for the given |value_offset|, a position in the output |
| 72 | // image in the direction we're convolving. The offset and length of the |
| 73 | // filter values are put into the corresponding out arguments (see AddFilter |
| 74 | // above for what these mean), and a pointer to the first scaling factor is |
| 75 | // returned. There will be |filter_length| values in this array. |
| 76 | inline const int16* FilterForValue(int value_offset, |
| 77 | int* filter_offset, |
| 78 | int* filter_length) const { |
| 79 | const FilterInstance& filter = filters_[value_offset]; |
| 80 | *filter_offset = filter.offset; |
| 81 | *filter_length = filter.length; |
| 82 | return &filter_values_[filter.data_location]; |
| 83 | } |
| 84 | |
| 85 | private: |
| 86 | struct FilterInstance { |
| 87 | // Offset within filter_values for this instance of the filter. |
| 88 | int data_location; |
| 89 | |
| 90 | // Distance from the left of the filter to the center. IN PIXELS |
| 91 | int offset; |
| 92 | |
| 93 | // Number of values in this filter instance. |
| 94 | int length; |
| 95 | }; |
| 96 | |
| 97 | // Stores the information for each filter added to this class. |
| 98 | std::vector<FilterInstance> filters_; |
| 99 | |
| 100 | // We store all the filter values in this flat list, indexed by |
| 101 | // |FilterInstance.data_location| to avoid the mallocs required for storing |
| 102 | // each one separately. |
| 103 | std::vector<int16> filter_values_; |
| 104 | |
| 105 | // The maximum size of any filter we've added. |
| 106 | int max_filter_; |
| 107 | }; |
| 108 | |
| 109 | // Does a two-dimensional convolusion on the given source image. |
| 110 | // |
| 111 | // It is assumed the source pixel offsets referenced in the input filters |
| 112 | // reference only valid pixels, so the source image size is not required. Each |
| 113 | // row of the source image starts |source_byte_row_stride| after the previous |
| 114 | // one (this allows you to have rows with some padding at the end). |
| 115 | // |
| 116 | // The result will be put into the given output buffer. The destination image |
| 117 | // size will be xfilter.num_values() * yfilter.num_values() pixels. It will be |
| 118 | // in rows of exactly xfilter.num_values() * 4 bytes. |
| 119 | // |
| 120 | // |source_has_alpha| is a hint that allows us to avoid doing computations on |
| 121 | // the alpha channel if the image is opaque. If you don't know, set this to |
| 122 | // true and it will work properly, but setting this to false will be a few |
| 123 | // percent faster if you know the image is opaque. |
| 124 | // |
| 125 | // The layout in memory is assumed to be 4-bytes per pixel in B-G-R-A order |
| 126 | // (this is ARGB when loaded into 32-bit words on a little-endian machine). |
| 127 | void BGRAConvolve2D(const uint8* source_data, |
| 128 | int source_byte_row_stride, |
| 129 | bool source_has_alpha, |
| 130 | const ConvolusionFilter1D& xfilter, |
| 131 | const ConvolusionFilter1D& yfilter, |
| 132 | uint8* output); |
| 133 | |
| 134 | } // namespace gfx |
| 135 | |
| 136 | #endif // BASE_GFX_CONVOLVER_H__ |
license.bot | f003cfe | 2008-08-24 09:55:55 +0900 | [diff] [blame^] | 137 | |