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33 ///////////////////////////////////////////////////////////////////////////
37 #ifndef INCLUDED_IMF_LUT_H
38 #define INCLUDED_IMF_LUT_H
40 //-----------------------------------------------------------------------------
42 // Lookup tables for efficient application
43 // of half --> half functions to pixel data,
44 // and some commonly applied functions.
46 //-----------------------------------------------------------------------------
48 #include <ImfRgbaFile.h>
49 #include <ImfFrameBuffer.h>
51 #include "halfFunction.h"
56 // Lookup table for individual half channels.
67 template <class Function>
71 //----------------------------------------------------------------------
72 // Apply the table to data[0], data[stride] ... data[(nData-1) * stride]
73 //----------------------------------------------------------------------
75 void apply (half *data,
77 int stride = 1) const;
80 //---------------------------------------------------------------
81 // Apply the table to a frame buffer slice (see ImfFrameBuffer.h)
82 //---------------------------------------------------------------
84 void apply (const Slice &data,
85 const Imath::Box2i &dataWindow) const;
89 halfFunction <half> _lut;
94 // Lookup table for combined RGBA data.
105 template <class Function>
106 RgbaLut (Function f, RgbaChannels chn = WRITE_RGB);
109 //----------------------------------------------------------------------
110 // Apply the table to data[0], data[stride] ... data[(nData-1) * stride]
111 //----------------------------------------------------------------------
113 void apply (Rgba *data,
115 int stride = 1) const;
118 //-----------------------------------------------------------------------
119 // Apply the table to a frame buffer (see RgbaOutpuFile.setFrameBuffer())
120 //-----------------------------------------------------------------------
122 void apply (Rgba *base,
125 const Imath::Box2i &dataWindow) const;
129 halfFunction <half> _lut;
135 // 12bit log rounding reduces data to 20 stops with 200 steps per stop.
136 // That makes 4000 numbers. An extra 96 just come along for the ride.
137 // Zero explicitly remains zero. The first non-zero half will map to 1
138 // in the 0-4095 12log space. A nice power of two number is placed at
139 // the center [2000] and that number is near 0.18.
142 half round12log (half x);
146 // Round to n-bit precision (n should be between 0 and 10).
147 // After rounding, the significand's 10-n least significant
148 // bits will be zero.
153 roundNBit (int n): n(n) {}
154 half operator () (half x) {return x.round(n);}
160 // Template definitions
164 template <class Function>
165 HalfLut::HalfLut (Function f):
166 _lut(f, -HALF_MAX, HALF_MAX, half (0),
167 half::posInf(), half::negInf(), half::qNan())
173 template <class Function>
174 RgbaLut::RgbaLut (Function f, RgbaChannels chn):
175 _lut(f, -HALF_MAX, HALF_MAX, half (0),
176 half::posInf(), half::negInf(), half::qNan()),