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41 #include "utils.h"
42
43 #include <assert.h>
44 #include <qglobal.h>
45
46 #include "qnum.h"
47
48 #define FloatToXFixed(i) (int)((i) * 65536)
49 #define IntToXFixed(i) ((i) << 16)
50
compute_x_at(XFixed y,XPointFixed p1,XPointFixed p2)51 static double compute_x_at(XFixed y, XPointFixed p1, XPointFixed p2)
52 {
53 double d = XFixedToDouble(p2.x - p1.x);
54 return
55 XFixedToDouble(p1.x) + d*XFixedToDouble(y - p1.y)/XFixedToDouble(p2.y - p1.y);
56 }
57
compute_area(XTrapezoid * trap)58 double compute_area(XTrapezoid *trap)
59 {
60 double x1 = compute_x_at(trap->top, trap->left.p1, trap->left.p2);
61 double x2 = compute_x_at(trap->top, trap->right.p1, trap->right.p2);
62 double x3 = compute_x_at(trap->bottom, trap->left.p1, trap->left.p2);
63 double x4 = compute_x_at(trap->bottom, trap->right.p1, trap->right.p2);
64
65 double top = XFixedToDouble(trap->top);
66 double bottom = XFixedToDouble(trap->bottom);
67 double h = bottom - top;
68
69 double top_base = x2 - x1;
70 double bottom_base = x4 - x3;
71
72 if ((top_base < 0 && bottom_base > 0)
73 || (top_base > 0 && bottom_base < 0)) {
74 double y0 = top_base*h/(top_base - bottom_base) + top;
75 double area = qAbs(top_base * (y0 - top) / 2.);
76 area += qAbs(bottom_base * (bottom - y0) /2.);
77 return area;
78 }
79
80
81 return 0.5 * h * qAbs(top_base + bottom_base);
82 }
83
compute_area_for_x(const QVector<XTrapezoid> & traps)84 double compute_area_for_x(const QVector<XTrapezoid> &traps)
85 {
86 double area = 0;
87
88 for (int i = 0; i < traps.size(); ++i) {
89 XTrapezoid trap = traps[i];
90 area += compute_area(&trap);
91 }
92 return area;
93 }
94