C语言 Bresenham 的线描代码
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原文地址: http://stackoverflow.com/questions/18761457/
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Bresenham's line drawing Code
提问by Lucy
I'm trying to draw a line in C language using Bresenham's algorithm.I'm using turbo C++ in dosbox for windows 7 to implement this code.While compiling i'm not getting any error but when i run the code the programs terminates after obtaining the 2 co-ordinates.Please Help..
我正在尝试使用 Bresenham 算法在 C 语言中画一条线。我在 Windows 7 的 dosbox 中使用 turbo C++ 来实现此代码。编译时我没有收到任何错误，但是当我运行代码时，程序终止获得2个坐标。请帮助..
the message on compiling is as follows..
编译消息如下..
the directories path is as follows
目录路径如下
My code..
我的代码..
# include <stdio.h>
# include <conio.h>
# include <graphics.h>
void main()
{
int dx,dy,x,y,p,x1,y1,x2,y2;
int gd,gm;
clrscr();
printf("\n\n\tEnter the co-ordinates of first point : ");
scanf("%d %d",&x1,&y1);
printf("\n\n\tEnter the co-ordinates of second point : ");
scanf("%d %d",&x2,&y2);
dx = (x2 - x1);
dy = (y2 - y1);
p = 2 * (dy) - (dx);
x = x1;
y = y1;
detectgraph(&gd,&gm);
initgraph(&gd,&gm,"e:\tc\bgi");
putpixel(x,y,WHITE);
while(x <= x2)
{
if(p < 0)
{
x=x+1;
y=y;
p = p + 2 * (dy);
}
else
{
x=x+1;
y=y+1;
p = p + 2 * (dy - dx);
}
putpixel(x,y,WHITE);
}
getch();
closegraph();
}
回答by chux - Reinstate Monica
OP should post input that was used.
OP 应该发布使用过的输入。
The posted sample code does not work is x1> x2nor y1> y2. This is one set of input that would stop the routine abruptly. To fix, the dxand dyshould be based on the absolute value and the incremental x& ysteps need to be independently +1or-1.
发布的示例代码不起作用x1>x2或y1> y2。这是一组会突然停止例程的输入。要修复，dx和dy应该基于绝对值，增量x和y步骤需要独立+1或-1。
An input of 3,4instead of 3 4(comma vs. whitespace) will also mess up the routine.
3,4而不是3 4（逗号与空格）的输入也会弄乱例程。
In the while loop, recommend if(p <= 0).
在 while 循环中，推荐if(p <= 0).
OP's "... code the programs terminates after obtaining the 2 co-ordinates." is not detailed enough, for of course the code shouldterminate sometime after obtaining the 2 co-ordinates. But OP does not detail where it terminates too early.
OP 的“...代码程序在获得 2 个坐标后终止。” 不够详细，因为当然代码应该在获得 2 个坐标后的某个时间终止。但是 OP 没有详细说明它过早终止的位置。
回答by Lucy
A way to rectify the problem is by changing the path in the initgraph function according to the address mentioned in the screenshot.
解决问题的一种方法是根据屏幕截图中提到的地址更改initgraph函数中的路径。
detectgraph(&gd,&gm);
initgraph(&gd,&gm,"C:\TURBOC3\bgi");
putpixel(x,y,WHITE);
回答by ashumeow
Nice program. But, you haven't initialized any loop as well as lines coded in while-loop were partially incorrect. Here is my try:-
不错的节目。但是，您还没有初始化任何循环以及在 while 循环中编码的行部分不正确。这是我的尝试：-
i = 1; // loop initialization
do {
putpixel(x, y, 15);
while(p >= 0) {
y = y + 1;
p = p - (2 * dx);
}
x = x + 1;
p = p + (2 * dy);
i = i + 1;
}
while(i <= dx);
回答by stefan_ah
This is a typical perfect point to start the debugger and go through the code step-by-step, watching any variables. If a debugger is unavailable, printf debugging to the console is a backup alternative.
这是启动调试器并逐步执行代码、观察任何变量的典型完美点。如果调试器不可用，printf 调试到控制台是一个备用选择。
A first tip is to check that these lines do not generate an error/exception:
第一个提示是检查这些行是否不会产生错误/异常：
detectgraph(&gd,&gm);
initgraph(&gd,&gm,"e:\tc\bgi");
putpixel(x,y,WHITE);
