C++画圆算法Algorithm DrawCircle

最新推荐文章于 2024-07-25 10:12:07 发布

原创最新推荐文章于 2024-07-25 10:12:07 发布 · 2.4k 阅读

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本文介绍了一种使用OpenGL ES实现美颜效果的方法，通过调整点的位置来绘制圆弧，适用于实时视频处理和直播特效应用。算法基于tangetial_factor和radial_factor计算新的点位坐标，以创建平滑的曲线。

原算法引用地址 http://slabode.exofire.net/circle_draw.shtml

懒得用画图软件直接用画图画一下
这里是用点来分割画出圆， num_segments 是点的个数这里theta =360/num_segments
x y,分别代表新的点位的坐标
y += ty * tangetial_factor; 这步就是求BC 因为AB长度为r r*tan( theta)

void DrawArc(float cx, float cy, float r, float start_angle, float arc_angle, int num_segments)
{
float theta = arc_angle / float(num_segments - 1);//theta is now calculated from the arc angle instead, the - 1 bit comes from the fact that the arc is open

float tangetial_factor = tanf(theta);

float radial_factor = cosf(theta);


float x = r * cosf(start_angle);//we now start at the start angle
float y = r * sinf(start_angle); 

glBegin(GL_LINE_STRIP);//since the arc is not a closed curve, this is a strip now
for(int ii = 0; ii < num_segments; ii++)
{ 
	glVertex2f(x + cx, y + cy);

	float tx = -y; 
	float ty = x; 

	x += tx * tangetial_factor; 
	y += ty * tangetial_factor; 

	x *= radial_factor; 
	y *= radial_factor; 
} 
glEnd();

}