100 lines
3.0 KiB
C++
100 lines
3.0 KiB
C++
#include "conic_gradient.h"
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#define INTERPOLATE_COLOR(C1, C2, t) (((C2) - (C1)) * (t) + (C1))
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static void sector_patch (cairo_pattern_t *pattern, double radius,
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double angle_A,
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double A_r, double A_g, double A_b, double A_a,
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double angle_B,
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double B_r, double B_g, double B_b, double B_a)
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{
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double r_sin_A, r_cos_A;
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double r_sin_B, r_cos_B;
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double h;
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r_sin_A = radius * sin (angle_A);
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r_cos_A = radius * cos (angle_A);
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r_sin_B = radius * sin (angle_B);
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r_cos_B = radius * cos (angle_B);
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h = 4.0/3.0 * tan ((angle_B - angle_A) / 4.0);
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double x0 = r_cos_A;
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double y0 = r_sin_A;
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double x1 = r_cos_A - h * r_sin_A;
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double y1 = r_sin_A + h * r_cos_A;
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double x2 = r_cos_B + h * r_sin_B;
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double y2 = r_sin_B - h * r_cos_B;
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double x3 = r_cos_B;
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double y3 = r_sin_B;
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cairo_mesh_pattern_begin_patch (pattern);
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cairo_mesh_pattern_move_to (pattern, 0, 0);
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cairo_mesh_pattern_line_to (pattern, x0, y0);
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cairo_mesh_pattern_curve_to (pattern,
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x1, y1,
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x2, y2,
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x3, y3);
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cairo_mesh_pattern_line_to (pattern, 0, 0);
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cairo_mesh_pattern_set_corner_color_rgba (pattern, 0, A_r, A_g, A_b, A_a);
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cairo_mesh_pattern_set_corner_color_rgba (pattern, 1, A_r, A_g, A_b, A_a);
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cairo_mesh_pattern_set_corner_color_rgba (pattern, 2, B_r, B_g, B_b, B_a);
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cairo_mesh_pattern_set_corner_color_rgba (pattern, 3, B_r, B_g, B_b, B_a);
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cairo_mesh_pattern_end_patch (pattern);
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}
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cairo_pattern_t* create_conic_gradient_pattern(double angle, double radius, const std::vector<bg_color_point>& color_points)
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{
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if (color_points.empty())
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{
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return nullptr;
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}
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if(color_points.size() == 2)
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{
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std::vector<bg_color_point> points;
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points.push_back(color_points[0]);
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bg_color_point cp;
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cp.offset = 0.5f;
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cp.color.red = INTERPOLATE_COLOR(color_points[0].color.red, color_points[1].color.red, 0.5f);
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cp.color.green = INTERPOLATE_COLOR(color_points[0].color.green, color_points[1].color.green, 0.5f);
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cp.color.blue = INTERPOLATE_COLOR(color_points[0].color.blue, color_points[1].color.blue, 0.5f);
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cp.color.alpha = INTERPOLATE_COLOR(color_points[0].color.alpha, color_points[1].color.alpha, 0.5f);
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points.push_back(cp);
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points.push_back(color_points[1]);
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return create_conic_gradient_pattern(angle, radius, points);
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}
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const double two_pi = 2.0 * M_PI;
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cairo_pattern_t* pattern = cairo_pattern_create_mesh();
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for(size_t i = 0; i < color_points.size() - 1; ++i)
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{
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const bg_color_point& cp_A = color_points[i];
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const bg_color_point& cp_B = color_points[i + 1];
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double angle_A = cp_A.offset * two_pi + angle;
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double angle_B = color_points[i + 1].offset * two_pi + angle;
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double A_r = cp_A.color.red / 255.0;
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double A_g = cp_A.color.green / 255.0;
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double A_b = cp_A.color.blue / 255.0;
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double A_a = cp_A.color.alpha / 255.0;
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double B_r = cp_B.color.red / 255.0;
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double B_g = cp_B.color.green / 255.0;
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double B_b = cp_B.color.blue / 255.0;
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double B_a = cp_B.color.alpha / 255.0;
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sector_patch(pattern, radius,
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angle_A, A_r, A_g, A_b, A_a,
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angle_B, B_r, B_g, B_b, B_a);
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}
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return pattern;
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}
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