Opengl__渐变画线

中点画线#

#include <GL/glut.h> 
#include<math.h>
#include<iostream>
using namespace std;
void Midpoint(float x0, float y0, float x1, float y1)
{
	int flag = 0;
	float a, b, d, x, y;
	//k>1
	if (abs(x1 - x0) < abs(y1 - y0)) {
		swap(x0, y0);
		swap(x1, y1);
		flag = 1;
	}
	if (x0 > x1) {
		swap(x0, x1);
		swap(y0, y1);
	}
	//窗口清为黑色
	glClear(GL_COLOR_BUFFER_BIT);
	a = y0 - y1;
	b = x1 - x0;
	d = 2 * a + b;
	if (y0 < y1) {//斜率为正
		x = x0;
		y = y0;
		//画点
		glBegin(GL_POINTS);
		GLfloat  n = x1 - x;
		GLfloat  cnt = 0;
		GLfloat colorChange = cnt / n;
		glColor3f(1.0, 0, 0);
		glVertex2f(x0 / 1000, y0 / 1000);
		glEnd();
	
		while (x < x1) {
			x++;
			cnt++;
			colorChange = cnt / n;
			if (d < 0) {
				y++;
				d += 2 * (a + b);
			}
			else {
				d += 2 * a;
			}
			if (flag == 1) {
				glBegin(GL_POINTS);
				glColor3f(1.0* colorChange, 0, 0);
				glVertex2f(y / 1000, x / 1000);
				glEnd();
			}
			else {
				glBegin(GL_POINTS);
				glColor3f(1.0 * colorChange, 0, 0);
				glVertex2f(x / 1000, y / 1000);
				glEnd();
			}
		}
		glFlush();
	}
	else {
		x = x1;
		y = y1;
		GLfloat  n = x-x0;
		GLfloat  cnt = 0;
		GLfloat colorChange = cnt / n;
		//画点
		glBegin(GL_POINTS);
		glColor3f(1.0 * colorChange, 0, 0);
		glVertex2f(x0 / 1000, y0 / 1000);
		glEnd();
		while (x > x0) {
			x--;
			cnt++;
		 colorChange = cnt / n;
			
			if (d < 0) {
				y++;
				d = d - 2 * a + 2 * b;
			}
			else {
				d = d - 2 * a;
			}
			if (flag == 1) {
				glBegin(GL_POINTS);
				glColor3f(1.0 * colorChange, 0, 0);
				glVertex2f(y / 1000, x / 1000);
				glEnd();
			}
			else {
				glBegin(GL_POINTS);
				glColor3f(1.0 * colorChange, 0, 0);
				glVertex2f(x / 1000, y / 1000);
				glEnd();
			}
		}
		glFlush();
	}
}

void display(void) {
	float x0, y0, x1, y1;
	cout << "请输入起始点和终点坐标" << endl;
	cin >> x0 >> y0 >> x1 >> y1;
	Midpoint(x0, y0, x1, y1);
}

void main(int argc, char** argv) {
	glutInit(&argc, argv); //初始化glut
	glutInitDisplayMode(GLUT_DEPTH | GLUT_SINGLE | GLUT_RGBA);
	//设置窗口的模式－深度缓存，单缓存，颜色模型
	glutInitWindowPosition(200, 200); //设置窗口的位置
	glutInitWindowSize(400, 400); //设置窗口的大小
	glutCreateWindow("Line"); //创建窗口并赋予title
	glutDisplayFunc(display);//调用display把绘制传送到窗口,这个函数的原型为glutDisplayFunc（void）
	glutMainLoop(); //进入循环等待
}

结果#

DDA算法#


void DDA(float x0, float y0, float x1, float y1) {
	float dm = 0;
	if (abs(x1-x0) < abs(y1 - y0)) {
		dm = abs(y1 - y0);
	}
	else dm = abs(x1 - x0);
	
	float dx = (float)(x1 - x0) / dm;
	float dy = (float ) (y1 - y0) / dm;
	float x = x0, y = y0;
	glPointSize(6.0f);
	GLfloat precise = 0.25;
	glBegin(GL_POINTS);
	for (float  i = 0; i < dm; i+=precise) {
		glColor3f(i/dm, 0, 0);
		x += dx * precise;
		y += dy * precise;
		glVertex2f(x , y );
	}
	glEnd();

}