305 lines
8.1 KiB
C++
305 lines
8.1 KiB
C++
//----------------------------------------------------------------------------
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// Anti-Grain Geometry - Version 2.4
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// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
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//
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// Permission to copy, use, modify, sell and distribute this software
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// is granted provided this copyright notice appears in all copies.
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// This software is provided "as is" without express or implied
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// warranty, and with no claim as to its suitability for any purpose.
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//
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//----------------------------------------------------------------------------
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// Contact: mcseem@antigrain.com
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// mcseemagg@yahoo.com
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// http://www.antigrain.com
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//----------------------------------------------------------------------------
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#ifndef AGG_GAMMA_LUT_INCLUDED
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#define AGG_GAMMA_LUT_INCLUDED
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#include <cmath>
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#include "agg_basics.h"
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#include "agg_gamma_functions.h"
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namespace agg
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{
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template<class LoResT=int8u,
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class HiResT=int8u,
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unsigned GammaShift=8,
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unsigned HiResShift=8> class gamma_lut
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{
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public:
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typedef gamma_lut<LoResT, HiResT, GammaShift, HiResShift> self_type;
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enum gamma_scale_e
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{
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gamma_shift = GammaShift,
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gamma_size = 1 << gamma_shift,
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gamma_mask = gamma_size - 1
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};
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enum hi_res_scale_e
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{
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hi_res_shift = HiResShift,
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hi_res_size = 1 << hi_res_shift,
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hi_res_mask = hi_res_size - 1
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};
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~gamma_lut()
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{
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pod_allocator<LoResT>::deallocate(m_inv_gamma, hi_res_size);
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pod_allocator<HiResT>::deallocate(m_dir_gamma, gamma_size);
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}
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gamma_lut() :
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m_gamma(1.0),
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m_dir_gamma(pod_allocator<HiResT>::allocate(gamma_size)),
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m_inv_gamma(pod_allocator<LoResT>::allocate(hi_res_size))
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{
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unsigned i;
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for(i = 0; i < gamma_size; i++)
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{
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m_dir_gamma[i] = HiResT(i << (hi_res_shift - gamma_shift));
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}
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for(i = 0; i < hi_res_size; i++)
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{
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m_inv_gamma[i] = LoResT(i >> (hi_res_shift - gamma_shift));
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}
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}
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gamma_lut(double g) :
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m_gamma(1.0),
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m_dir_gamma(pod_allocator<HiResT>::allocate(gamma_size)),
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m_inv_gamma(pod_allocator<LoResT>::allocate(hi_res_size))
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{
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gamma(g);
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}
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void gamma(double g)
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{
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m_gamma = g;
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unsigned i;
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for(i = 0; i < gamma_size; i++)
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{
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m_dir_gamma[i] = (HiResT)
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uround(pow(i / double(gamma_mask), m_gamma) * double(hi_res_mask));
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}
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double inv_g = 1.0 / g;
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for(i = 0; i < hi_res_size; i++)
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{
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m_inv_gamma[i] = (LoResT)
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uround(pow(i / double(hi_res_mask), inv_g) * double(gamma_mask));
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}
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}
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double gamma() const
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{
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return m_gamma;
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}
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HiResT dir(LoResT v) const
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{
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return m_dir_gamma[unsigned(v)];
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}
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LoResT inv(HiResT v) const
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{
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return m_inv_gamma[unsigned(v)];
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}
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private:
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gamma_lut(const self_type&);
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const self_type& operator = (const self_type&);
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double m_gamma;
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HiResT* m_dir_gamma;
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LoResT* m_inv_gamma;
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};
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//
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// sRGB support classes
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//
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// Optimized sRGB lookup table. The direct conversion (sRGB to linear)
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// is a straightforward lookup. The inverse conversion (linear to sRGB)
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// is implemented using binary search.
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template<class LinearType>
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class sRGB_lut_base
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{
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public:
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LinearType dir(int8u v) const
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{
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return m_dir_table[v];
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}
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int8u inv(LinearType v) const
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{
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// Unrolled binary search.
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int8u x = 0;
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if (v > m_inv_table[128]) x = 128;
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if (v > m_inv_table[x + 64]) x += 64;
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if (v > m_inv_table[x + 32]) x += 32;
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if (v > m_inv_table[x + 16]) x += 16;
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if (v > m_inv_table[x + 8]) x += 8;
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if (v > m_inv_table[x + 4]) x += 4;
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if (v > m_inv_table[x + 2]) x += 2;
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if (v > m_inv_table[x + 1]) x += 1;
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return x;
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}
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protected:
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LinearType m_dir_table[256];
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LinearType m_inv_table[256];
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// Only derived classes may instantiate.
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sRGB_lut_base()
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{
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}
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};
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// sRGB_lut - implements sRGB conversion for the various types.
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// Base template is undefined, specializations are provided below.
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template<class LinearType>
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class sRGB_lut;
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template<>
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class sRGB_lut<float> : public sRGB_lut_base<float>
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{
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public:
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sRGB_lut()
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{
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// Generate lookup tables.
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m_dir_table[0] = 0;
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m_inv_table[0] = 0;
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for (unsigned i = 1; i <= 255; ++i)
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{
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// Floating-point RGB is in range [0,1].
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m_dir_table[i] = float(sRGB_to_linear(i / 255.0));
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m_inv_table[i] = float(sRGB_to_linear((i - 0.5) / 255.0));
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}
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}
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};
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template<>
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class sRGB_lut<int16u> : public sRGB_lut_base<int16u>
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{
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public:
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sRGB_lut()
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{
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// Generate lookup tables.
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m_dir_table[0] = 0;
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m_inv_table[0] = 0;
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for (unsigned i = 1; i <= 255; ++i)
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{
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// 16-bit RGB is in range [0,65535].
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m_dir_table[i] = uround(65535.0 * sRGB_to_linear(i / 255.0));
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m_inv_table[i] = uround(65535.0 * sRGB_to_linear((i - 0.5) / 255.0));
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}
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}
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};
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template<>
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class sRGB_lut<int8u> : public sRGB_lut_base<int8u>
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{
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public:
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sRGB_lut()
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{
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// Generate lookup tables.
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m_dir_table[0] = 0;
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m_inv_table[0] = 0;
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for (unsigned i = 1; i <= 255; ++i)
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{
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// 8-bit RGB is handled with simple bidirectional lookup tables.
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m_dir_table[i] = uround(255.0 * sRGB_to_linear(i / 255.0));
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m_inv_table[i] = uround(255.0 * linear_to_sRGB(i / 255.0));
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}
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}
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int8u inv(int8u v) const
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{
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// In this case, the inverse transform is a simple lookup.
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return m_inv_table[v];
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}
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};
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// Common base class for sRGB_conv objects. Defines an internal
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// sRGB_lut object so that users don't have to.
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template<class T>
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class sRGB_conv_base
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{
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public:
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static T rgb_from_sRGB(int8u x)
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{
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return lut.dir(x);
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}
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static int8u rgb_to_sRGB(T x)
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{
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return lut.inv(x);
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}
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private:
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static sRGB_lut<T> lut;
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};
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// Definition of sRGB_conv_base::lut. Due to the fact that this a template,
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// we don't need to place the definition in a cpp file. Hurrah.
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template<class T>
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sRGB_lut<T> sRGB_conv_base<T>::lut;
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// Wrapper for sRGB-linear conversion.
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// Base template is undefined, specializations are provided below.
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template<class T>
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class sRGB_conv;
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template<>
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class sRGB_conv<float> : public sRGB_conv_base<float>
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{
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public:
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static float alpha_from_sRGB(int8u x)
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{
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return float(x / 255.0);
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}
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static int8u alpha_to_sRGB(float x)
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{
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if (x <= 0) return 0;
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else if (x >= 1) return 255;
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else return int8u(0.5 + x * 255);
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}
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};
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template<>
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class sRGB_conv<int16u> : public sRGB_conv_base<int16u>
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{
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public:
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static int16u alpha_from_sRGB(int8u x)
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{
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return (x << 8) | x;
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}
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static int8u alpha_to_sRGB(int16u x)
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{
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return x >> 8;
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}
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};
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template<>
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class sRGB_conv<int8u> : public sRGB_conv_base<int8u>
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{
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public:
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static int8u alpha_from_sRGB(int8u x)
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{
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return x;
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}
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static int8u alpha_to_sRGB(int8u x)
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{
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return x;
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}
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};
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}
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#endif
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