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307 lines
8.0 KiB
307 lines
8.0 KiB
//---------------------------------------------------------------------------- |
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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(std::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(std::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 (int 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 (int 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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static const double y = 1 / 255.0; |
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return float(x * y); |
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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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if (x > 1) return 255; |
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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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