绘制圆圈(使用带有for循环的图像中应用的像素)

Question

我想使用像素位置绘制一个圆圈(带有1或2个循环)(从左上角开始到右下角结束)

我用这个方法成功绘制了一个矩形:

private void drawrect(int width,int height,int x,int y) {
    int top=y;
    int left=x;

    if(top<0){
        height+=top;
        top=0;
        }
    if(left<0){
        width+=left;
        left=0;
    }

    for (int j = 0; j <width; j++) {
        for (int i = 0; i <height; i++) {
                    pixels[((i+top)*w)+j+left] = 0xffffff;//white color
        }

    }

}

像素数组包含像素索引,后跟颜色.

pixels[index]=color;

在此之前,我将此代码用于"图像"和"像素"数组(如果这对您有帮助)

img = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
pixels = ((DataBufferInt) img.getRaster().getDataBuffer()).getData();

但是,如何只绘制此图像中的白色像素并忽略其他像素？

Pixel Image http://oi42.tinypic.com/2u61sud.jpg

Answer 1

下面是用像素绘制圆的代码:它使用公式xend = x + r cos(角度)和yend = y + r sin(角度).

#include <stdio.h>
#include <graphics.h>
#include <stdlib.h>
#include <conio.h>
#include <bios.h>
#include <math.h>

void DrawCircle(int x, int y, int r, int color)
{
      static const double PI = 3.1415926535;
      double i, angle, x1, y1;

      for(i = 0; i < 360; i += 0.1)
      {
            angle = i;
            x1 = r * cos(angle * PI / 180);
            y1 = r * sin(angle * PI / 180);
            putpixel(x + x1, y + y1, color);
      }
}

参考:http://www.softwareandfinance.com/Turbo_C/DrawCircle.html

Answer 2

您可以计算两个像素之间的最小角度并改进 Kathir 解决方案

...
void DrawCircle(int x, int y, int r, int color)
{
      static const double PI = 3.1415926535;
      double x1, y1;

      // calculates the minimun angle between two pixels in a diagonal.
      // you can multiply minAngle by a security factor like 0.9 just to be sure you wont have empty pixels in the circle
      double minAngle = acos(1 - 1/r);

      for(double angle = 0; angle <= 360; angle += minAngle)
      {
            x1 = r * cos(angle);
            y1 = r * sin(angle);
            putpixel(x + x1, y + y1, color);
      }
}