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Bitmap/Bézier curves/Cubic: Difference between revisions
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Using the data storage type defined [[Basic_bitmap_storage|on this page]] for raster images, and the <code>draw_line</code> function defined in [[Bresenham's_line_algorithm|this other one]], draw a '''cubic bezier curves'''
([http://en.wikipedia.org/wiki/Bezier_curves#Cubic_B.C3.A9zier_curves definition on Wikipedia]).
=={{header|C}}==
<C>#define plot(x, y) put_pixel_clip(img, x, y, r, g, b)
#define line(x0,y0,x1,y1) draw_line(img, x0,y0,x1,y1, r,g,b)
void cubic_bezier(
image img,
unsigned int x1, unsigned int y1,
unsigned int x2, unsigned int y2,
unsigned int x3, unsigned int y3,
unsigned int x4, unsigned int y4,
color_component r,
color_component g,
color_component b )
{
unsigned int i;
double pts[N_SEG+1][2];
for (i=0; i <= N_SEG; ++i)
{
double t = (double)i / (double)N_SEG;
double a = pow((1.0 - t), 3.0);
double b = 3.0 * t * pow((1.0 - t), 2.0);
double c = 3.0 * pow(t, 2.0) * (1.0 - t);
double d = pow(t, 3.0);
double x = a * x1 + b * x2 + c * x3 + d * x4;
double y = a * y1 + b * y2 + c * y3 + d * y4;
pts[i][0] = x;
pts[i][1] = y;
}
#if 0
/* draw only points */
for (i=0; i <= N_SEG; ++i)
{
plot( pts[i][0],
pts[i][1] );
}
#else
/* draw segments */
for (i=0; i < N_SEG; ++i)
{
int j = i + 1;
line( pts[i][0], pts[i][1],
pts[j][0], pts[j][1] );
}
#endif
}
#undef plot
#undef line</C>
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