最近学习Bresenham算法画直线
算法原理的详细描述及部分实现可参考:
http://www.cs.helsinki.fi/group/goa/mallinnus/lines/bresenh.html
示例1:
引用:bresenham画线算法_Bresenham的C和C ++线条画算法
问题: 只能画第一象限, 倾角0到45度的直线,没有列全。
void drawline(int x0, int y0, int x1, int y1)
{
int dx, dy, p, x, y;
dx = x1 - x0;
dy = y1 - y0;
x = x0;
y = y0;
p = 2 * dy - dx;
while (x < x1)
{
if (p >= 0)
{
setPixel(x, y, 7);
y = y + 1;
p = p + 2 * dy - 2 * dx;
}
else
{
setPixel(x, y, 7);
p = p + 2 * dy;
}
x = x + 1;
}
}
示例2:
问题:
倾角大于45度小于90度的直线不连续
示例3:
引用:Bresenham快速画直线算法
引用的说明图片:
代码:
// Byte : unsigned char 1 char
typedef unsigned char Byte;
Byte ** m_ppItem; 为数据存储区,行优先
rows 和 cols是矩阵的行数和列数
int MatrixByte::setPixel(int x, int y, Byte value)
{
// range check
if (x < 0 || x >= cols || y < 0 || y >= rows)
return 0;
Byte *p = m_ppItem[y] + x;
if (*p == value)
return 0;
*p = value;
return 1;
}
//--------------------------------------------------------------------
int MatrixByte::lineBres(int x0, int y0, int x1, int y1)
{
int dx = x1 - x0;
int dy = y1 - y0;
int ux = ((dx > 0) << 1) - 1;
int uy = ((dy > 0) << 1) - 1;
int x = x0, y = y0, eps;
eps = 0;
dx = abs(dx);
dy = abs(dy);
int counter = 0; // count
if (dx > dy)
{
for (x = x0; x != x1; x += ux)
{
counter += setPixel(x, y, 0);
eps += dy;
if ((eps << 1) >= dx)
{
y += uy;
eps -= dx;
}
}
}
else
{
for (y = y0; y != y1; y += uy)
{
counter += setPixel(x, y, 0);
eps += dx;
if ((eps << 1) >= dy)
{
x += ux;
eps -= dy;
}
}
}
return counter;
}
#define PI 3.1415927F
void main()
{
....
MatrixByte matrix=MatrixByte(200,180);
... 为定义矩阵的代码,略
float da = PI / 10;
int x0 = 100;
int y0 = 100;
int r = 90;
float angle = 0;
for (int i = 0; i < 36; i++)
{
int x = x0 + (int)(r * cos(angle));
int y = y0 + (int)(r * sin(angle));
matrix.lineBres(x0, y0, x, y);
angle += da;
}
}
看起来不错。