更新时间：2016-06-13 13:56:10浏览次数：1+次
GDI抗锯齿也叫作GDI消除锯齿，还叫做GDI反锯齿，说的都是一个意思，就是GDI绘制的让非直线产生明显锯齿淡化，形成圆滑的线条。
Windows的GDI绘图时，当绘制了非直线时，会产生大量的锯齿，让线条非常不美观。可以看看下面的对比图：
【斜线】
【椭圆】
【圆弧】
上面的图片对比很明显，斜线和弧线产生的锯齿非常明显。所以有时候对美观要求比较高时，就需要消除锯齿了。而GDI本身并不提供消除锯齿的解决办法，所以必须自己写算法消除，或者使用GDI+来绘图。如果必须用GDI，目前网上很难找到GDI消除锯齿的办法，找到大量的都是询问如何消除锯齿的提问。
我曾经也是一度寻求办法，后来在国外的一个网站找到了可行的解决方案，使用了之后发现很不错。不过你需要清楚一点，消除锯齿因为需要进行大量的运算，所以是比较消耗CPU的，所以绘制圆滑曲线相对于简单的带有锯齿的曲线更耗费资源和时间。在美观和性能方面，需要做一个取舍。
下面是GDI消除锯齿（GDI抗锯齿、GDI反锯齿）的代码，源码仅供学习交流使用，请勿商用：
头文件TGraphics.h：
// TGraphics.h: interface for the CTGraphics class.
// 本源码由C++技术网（http://www.cjjjs.com）提供
// 源码由国外作者编写，C++技术网主动推广使用，降低技术门槛
// 如有版权问题，C++技术网概不负责，仅作为学习交流使用，请勿商用
//////////////////////////////////////////////////////////////////////
#if !defined(TGRAPHICS_H)
#define TGRAPHICS_H
class CTGraphics
{
public:
CTGraphics();
virtual ~CTGraphics();
public:
// CTGraphics class interface
void DrawLine(HDC hDC, int x1, int y1, int x2, int y2, COLORREF color);
void DrawPolyline(HDC hDC, POINT* points, int numberPoints, COLORREF color);
void DrawPolygon(HDC hDC, POINT* points, int numberPoints, COLORREF color);
void DrawEllipse(HDC hDC, int x1, int y1, int x2, int y2, COLORREF color);
void DrawArc(HDC hDC, int x1, int y1, int x2, int y2, float startAngle, float endAngle, COLORREF color);
void DrawPie(HDC hDC, int x1, int y1, int x2, int y2, float startAngle, float endAngle, COLORREF color);
void DrawChord(HDC hDC, int x1, int y1, int x2, int y2, float startAngle, float endAngle, COLORREF color);
void DrawRoundRect(HDC hDC, int x1, int y1, int x2, int y2, int width, int height, COLORREF color);
void DrawBezier(HDC hDC, POINT* points, int numPoints, COLORREF color);
};
#endif // !defined(TGRAPHICS_H)
// TGraphics.cpp: implementation of the CTGraphics class.
// 本源码由C++技术网（http://www.cjjjs.com）提供
// 源码由国外作者编写，C++技术网主动推广使用，降低技术门槛
// 如有版权问题，C++技术网概不负责，仅作为学习交流使用，请勿商用
//////////////////////////////////////////////////////////////////////
#include "stdafx.h"
#include "TGraphics.h"
#include "math.h"
CTGraphics::CTGraphics()
{
}
CTGraphics::~CTGraphics()
{
}
void CTGraphics::DrawLine(HDC hDC, int x1, int y1, int x2, int y2, COLORREF color)
{
// Calculate line params
int dx = (x2 - x1);
int dy = (y2 - y1);
COLORREF bgColor;
int temp;
float k;
// Set start pixel
::SetPixel(hDC, x1, y1, color);
// X-dominant line
if (abs(dx) > abs(dy))
{
// Ex-change line end points
if (dx < 0)
{
temp = x1;
x1 = x2;
x2 = temp;
temp = y1;
y1 = y2;
y2 = temp;
}
k = (float)dy / (float)dx;
// Set middle pixels
int xs;
float yt = (float)y1 + k;
float distance;
UCHAR red, green, blue;
for (xs=x1+1; xs<x2; xs++)
{
distance = (float)(yt - (int)(yt));
bgColor = ::GetPixel(hDC, xs, (int)yt);
red = (UCHAR)(distance*GetRValue(bgColor)) + (UCHAR)((1.0f-distance)*GetRValue(color));
green = (UCHAR)(distance*GetGValue(bgColor)) + (UCHAR)((1.0f-distance)*GetGValue(color));
blue = (UCHAR)(distance*GetBValue(bgColor)) + (UCHAR)((1.0f-distance)*GetBValue(color));
::SetPixel(hDC, xs, (int)yt, RGB(red,green,blue));
bgColor = ::GetPixel(hDC, xs, (int)yt+1);
red = (UCHAR)((1.0f-distance)*GetRValue(bgColor)) + (UCHAR)(distance*GetRValue(color));
green = (UCHAR)((1.0f-distance)*GetGValue(bgColor)) + (UCHAR)(distance*GetGValue(color));
blue = (UCHAR)((1.0f-distance)*GetBValue(bgColor)) + (UCHAR)(distance*GetBValue(color));
::SetPixel(hDC, xs, (int)yt+1, RGB(red,green,blue));
yt += k;
}
}
// Y-dominant line
else
{
// Ex-change line end points
if (dy < 0)
{
temp = x1;
x1 = x2;
x2 = temp;
temp = y1;
y1 = y2;
y2 = temp;
}
k = (float)dx / (float)dy;
// Set middle pixels
int ys;
float xt = (float)x1 + k;
float distance;
UCHAR red, green, blue;
for (ys=y1+1; ys<y2; ys++)
{
distance = (float)(xt - (int)(xt));
bgColor = ::GetPixel(hDC, (int)xt, ys);
red = (UCHAR)(distance*GetRValue(bgColor)) + (UCHAR)((1.0f-distance)*GetRValue(color));
green = (UCHAR)(distance*GetGValue(bgColor)) + (UCHAR)((1.0f-distance)*GetGValue(color));
blue = (UCHAR)(distance*GetBValue(bgColor)) + (UCHAR)((1.0f-distance)*GetBValue(color));
::SetPixel(hDC, (int)xt, ys, RGB(red,green,blue));
bgColor = ::GetPixel(hDC, (int)xt+1, ys);
red = (UCHAR)((1.0f-distance)*GetRValue(bgColor)) + (UCHAR)(distance*GetRValue(color));
green = (UCHAR)((1.0f-distance)*GetGValue(bgColor)) + (UCHAR)(distance*GetGValue(color));
blue = (UCHAR)((1.0f-distance)*GetBValue(bgColor)) + (UCHAR)(distance*GetBValue(color));
::SetPixel(hDC, (int)xt+1, ys, RGB(red,green,blue));
xt += k;
}
}
// Set end pixel
::SetPixel(hDC, x2, y2, color);
}
void CTGraphics::DrawPolyline(HDC hDC, POINT* points, int numberPoints, COLORREF color)
{
for (int i=0; i<numberPoints-1; i++)
{
DrawLine(hDC, points[i].x, points[i].y, points[i+1].x, points[i+1].y, color);
}
}
void CTGraphics::DrawPolygon(HDC hDC, POINT* points, int numberPoints, COLORREF color)
{
DrawPolyline(hDC, points, numberPoints, color);
DrawLine(hDC, points[0].x, points[0].y, points[numberPoints-1].x, points[numberPoints-1].y, color);
}
void CTGraphics::DrawEllipse(HDC hDC, int x1, int y1, int x2, int y2, COLORREF color)
{
int centerX = (x1 + x2) / 2;
int centerY = (y1 + y2) / 2;
int dx = (x2 - x1);
int dy = (y2 - y1);
int radiusX = (int)(fabs((double)dx) / 2.0f);
int radiusY = (int)(fabs((double)dy) / 2.0f);
float rel = (float)sqrt((double)(radiusX*radiusX + radiusY*radiusY)) / (float)radiusY;
COLORREF bgColor;
int temp;
float distance;
UCHAR red, green, blue;
if (x2 < x1)
{
temp = x1;
x1 = x2;
x2 = temp;
temp = y1;
y1 = y2;
y2 = temp;
}
int xs;
float yt;
for (xs=-radiusX; xs<=radiusX; xs++)
{
yt = (float)(radiusY * sqrt(1-(float)(xs*xs)/(float)(radiusX*radiusX)));
distance = (float)(yt - (int)yt);
bgColor = ::GetPixel(hDC, centerX+xs, centerY+(int)yt);
red = (UCHAR)(distance*GetRValue(bgColor)) + (UCHAR)((1.0f-distance)*GetRValue(color));
green = (UCHAR)(distance*GetGValue(bgColor)) + (UCHAR)((1.0f-distance)*GetGValue(color));
blue = (UCHAR)(distance*GetBValue(bgColor)) + (UCHAR)((1.0f-distance)*GetBValue(color));
::SetPixel(hDC, centerX+xs, centerY+(int)yt, RGB(red,green,blue));
bgColor = ::GetPixel(hDC, centerX+xs, centerY+(int)yt+1);
red = (UCHAR)((1.0f-distance)*GetRValue(bgColor)) + (UCHAR)(distance*GetRValue(color));
green = (UCHAR)((1.0f-distance)*GetGValue(bgColor)) + (UCHAR)(distance*GetGValue(color));
blue = (UCHAR)((1.0f-distance)*GetBValue(bgColor)) + (UCHAR)(distance*GetBValue(color));
::SetPixel(hDC, centerX+xs, centerY+(int)yt+1, RGB(red,green,blue));
bgColor = ::GetPixel(hDC, centerX-xs, centerY-(int)yt);
red = (UCHAR)(distance*GetRValue(bgColor)) + (UCHAR)((1.0f-distance)*GetRValue(color));
green = (UCHAR)(distance*GetGValue(bgColor)) + (UCHAR)((1.0f-distance)*GetGValue(color));
blue = (UCHAR)(distance*GetBValue(bgColor)) + (UCHAR)((1.0f-distance)*GetBValue(color));
::SetPixel(hDC, centerX-xs, centerY-(int)yt, RGB(red,green,blue));
bgColor = ::GetPixel(hDC, centerX-xs, centerY-(int)yt-1);
red = (UCHAR)((1.0f-distance)*GetRValue(bgColor)) + (UCHAR)(distance*GetRValue(color));
green = (UCHAR)((1.0f-distance)*GetGValue(bgColor)) + (UCHAR)(distance*GetGValue(color));
blue = (UCHAR)((1.0f-distance)*GetBValue(bgColor)) + (UCHAR)(distance*GetBValue(color));
::SetPixel(hDC, centerX-xs, centerY-(int)yt-1, RGB(red,green,blue));
}
int ys;
float xt;
for (ys=-(int)((float)radiusY/rel); ys<=(int)((float)radiusY/rel); ys++)
{
xt = (float)(radiusX * sqrt(1-(float)(ys*ys)/(float)(radiusY*radiusY)));
distance = (float)(xt - (int)xt);
bgColor = ::GetPixel(hDC, centerX+(int)xt, centerY+ys);
red = (UCHAR)(distance*GetRValue(bgColor)) + (UCHAR)((1.0f-distance)*GetRValue(color));
green = (UCHAR)(distance*GetGValue(bgColor)) + (UCHAR)((1.0f-distance)*GetGValue(color));
blue = (UCHAR)(distance*GetBValue(bgColor)) + (UCHAR)((1.0f-distance)*GetBValue(color));
::SetPixel(hDC, centerX+(int)xt, centerY+ys, RGB(red,green,blue));
bgColor = ::GetPixel(hDC, centerX+(int)xt+1, centerY+ys);
red = (UCHAR)((1.0f-distance)*GetRValue(bgColor)) + (UCHAR)(distance*GetRValue(color));
green = (UCHAR)((1.0f-distance)*GetGValue(bgColor)) + (UCHAR)(distance*GetGValue(color));
blue = (UCHAR)((1.0f-distance)*GetBValue(bgColor)) + (UCHAR)(distance*GetBValue(color));
::SetPixel(hDC, centerX+(int)xt+1, centerY+ys, RGB(red,green,blue));
bgColor = ::GetPixel(hDC, centerX-(int)xt, centerY-ys);
red = (UCHAR)(distance*GetRValue(bgColor)) + (UCHAR)((1.0f-distance)*GetRValue(color));
green = (UCHAR)(distance*GetGValue(bgColor)) + (UCHAR)((1.0f-distance)*GetGValue(color));
blue = (UCHAR)(distance*GetBValue(bgColor)) + (UCHAR)((1.0f-distance)*GetBValue(color));
::SetPixel(hDC, centerX-(int)xt, centerY-ys, RGB(red,green,blue));
bgColor = ::GetPixel(hDC, centerX-(int)xt-1, centerY-ys);
red = (UCHAR)((1.0f-distance)*GetRValue(bgColor)) + (UCHAR)(distance*GetRValue(color));
green = (UCHAR)((1.0f-distance)*GetGValue(bgColor)) + (UCHAR)(distance*GetGValue(color));
blue = (UCHAR)((1.0f-distance)*GetBValue(bgColor)) + (UCHAR)(distance*GetBValue(color));
::SetPixel(hDC, centerX-(int)xt-1, centerY-ys, RGB(red,green,blue));
}
}
void CTGraphics::DrawArc(HDC hDC, int x1, int y1, int x2, int y2, float startAngle, float endAngle, COLORREF color)
{
int centerX = (x1 + x2) / 2;
int centerY = (y1 + y2) / 2;
int dx = (x2 - x1);
int dy = (y2 - y1);
int radiusX = (abs(dx) / 2);
int radiusY = (abs(dy) / 2);
COLORREF bgColor;
float distance;
UCHAR red, green, blue;
float angle = 0.0f;
while ((angle+90.0f) < startAngle)
angle += 90.0f;
while (angle < endAngle)
{
if (startAngle >= angle)
{
float eAngle;
if (endAngle <= angle+90.0f)
eAngle = endAngle;
else
eAngle = angle+90.0f;
float sx = (float)(radiusX*cos((startAngle/180.0f)*3.1415f));
if (sx > 0.0f)
sx += 0.5f;
else
sx -= 0.5f;
int startX = (int)sx;
int endX = (int)(radiusX*cos((eAngle/180.0f)*3.1415f));
int deltaX;
if (endX - startX != 0)
deltaX = (int)((endX-startX) / fabs((double)(endX-startX)));
else
deltaX = 0;
float sy = (float)(radiusY*sin((startAngle/180.0f)*3.1415f));
if (sy > 0.0f)
sy += 0.5f;
else
sy -= 0.5f;
int startY = (int)sy;
int endY = (int)(radiusY*sin((eAngle/180.0f)*3.1415f));
int deltaY;
if (endY - startY != 0)
deltaY = (int)((endY-startY) / fabs((double)(endY-startY)));
else
deltaY = 0;
if (deltaX != 0)
{
int oldY = startY;
int xs = startX;
float yt;
while (xs != endX)
{
yt = (float)(radiusY * sqrt(1.0f-(float)(xs*xs)/(float)(radiusX*radiusX)));
distance = (float)(yt - (int)yt);
if (abs(oldY - (int)yt) < 2)
{
if (deltaX < 0)
{
if (deltaY > 0)
bgColor = ::GetPixel(hDC, centerX+xs, centerY+(int)yt);
else
bgColor = ::GetPixel(hDC, centerX+xs, centerY+(int)yt);
}
else
{
if (deltaY < 0)
bgColor = ::GetPixel(hDC, centerX+xs, centerY-(int)yt);
else
bgColor = ::GetPixel(hDC, centerX+xs, centerY-(int)yt);
}
red = (UCHAR)(distance*GetRValue(bgColor)) + (UCHAR)((1.0f-distance)*GetRValue(color));
green = (UCHAR)(distance*GetGValue(bgColor)) + (UCHAR)((1.0f-distance)*GetGValue(color));
blue = (UCHAR)(distance*GetBValue(bgColor)) + (UCHAR)((1.0f-distance)*GetBValue(color));
if (deltaX < 0)
{
if (deltaY > 0)
::SetPixel(hDC, centerX+xs, centerY+(int)yt, RGB(red,green,blue));
else
::SetPixel(hDC, centerX+xs, centerY+(int)yt, RGB(red,green,blue));
}
else
{
if (deltaY < 0)
::SetPixel(hDC, centerX+xs, centerY-(int)yt, RGB(red,green,blue));
else
::SetPixel(hDC, centerX+xs, centerY-(int)yt, RGB(red,green,blue));
}
if (deltaX < 0)
{
if (deltaY > 0)
bgColor = ::GetPixel(hDC, centerX+xs, centerY+(int)yt+1);
else
bgColor = ::GetPixel(hDC, centerX+xs, centerY+(int)yt+1);
}
else
{
if (deltaY < 0)
bgColor = ::GetPixel(hDC, centerX+xs, centerY-(int)yt-1);
else
bgColor = ::GetPixel(hDC, centerX+xs, centerY-(int)yt-1);
}
red = (UCHAR)((1.0f-distance)*GetRValue(bgColor)) + (UCHAR)(distance*GetRValue(color));
green = (UCHAR)((1.0f-distance)*GetGValue(bgColor)) + (UCHAR)(distance*GetGValue(color));
blue = (UCHAR)((1.0f-distance)*GetBValue(bgColor)) + (UCHAR)(distance*GetBValue(color));
if (deltaX < 0)
{
if (deltaY > 0)
::SetPixel(hDC, centerX+xs, centerY+(int)yt+1, RGB(red,green,blue));
else
::SetPixel(hDC, centerX+xs, centerY+(int)yt+1, RGB(red,green,blue));
}
else
{
if (deltaY < 0)
::SetPixel(hDC, centerX+xs, centerY-(int)yt-1, RGB(red,green,blue));
else
::SetPixel(hDC, centerX+xs, centerY-(int)yt-1, RGB(red,green,blue));
}
}
oldY = (int)yt;
xs += deltaX;
}
}
if (deltaY != 0)
{
int oldX = startX;
int ys = startY;
float xt;
while (ys != endY)
{
xt = (float)(radiusX * sqrt(1.0f-(float)(ys*ys)/(float)(radiusY*radiusY)));
distance = (float)(xt - (int)xt);
if (abs(oldX - (int)xt) < 2)
{
if (deltaX < 0)
{
if (deltaY > 0)
bgColor = ::GetPixel(hDC, centerX+(int)xt, centerY+ys);
else
bgColor = ::GetPixel(hDC, centerX-(int)xt, centerY+ys);
}
else
{
if (deltaY < 0)
bgColor = ::GetPixel(hDC, centerX-(int)xt, centerY+ys);
else
bgColor = ::GetPixel(hDC, centerX+(int)xt, centerY+ys);
}
red = (UCHAR)(distance*GetRValue(bgColor)) + (UCHAR)((1.0f-distance)*GetRValue(color));
green = (UCHAR)(distance*GetGValue(bgColor)) + (UCHAR)((1.0f-distance)*GetGValue(color));
blue = (UCHAR)(distance*GetBValue(bgColor)) + (UCHAR)((1.0f-distance)*GetBValue(color));
if (deltaX < 0)
{
if (deltaY > 0)
::SetPixel(hDC, centerX+(int)xt, centerY+ys, RGB(red,green,blue));
else
::SetPixel(hDC, centerX-(int)xt, centerY+ys, RGB(red,green,blue));
}
else
{
if (deltaY < 0)
::SetPixel(hDC, centerX-(int)xt, centerY+ys, RGB(red,green,blue));
else
::SetPixel(hDC, centerX+(int)xt, centerY+ys, RGB(red,green,blue));
}
if (deltaX < 0)
{
if (deltaY > 0)
bgColor = ::GetPixel(hDC, centerX+(int)xt+1, centerY+ys);
else
bgColor = ::GetPixel(hDC, centerX-(int)xt-1, centerY+ys);
}
else
{
if (deltaY < 0)
bgColor = ::GetPixel(hDC, centerX-(int)xt-1, centerY+ys);
else
bgColor = ::GetPixel(hDC, centerX+(int)xt+1, centerY+ys);
}
red = (UCHAR)((1.0f-distance)*GetRValue(bgColor)) + (UCHAR)(distance*GetRValue(color));
green = (UCHAR)((1.0f-distance)*GetGValue(bgColor)) + (UCHAR)(distance*GetGValue(color));
blue = (UCHAR)((1.0f-distance)*GetBValue(bgColor)) + (UCHAR)(distance*GetBValue(color));
if (deltaX < 0)
{
if (deltaY > 0)
::SetPixel(hDC, centerX+(int)xt+1, centerY+ys, RGB(red,green,blue));
else
::SetPixel(hDC, centerX-(int)xt-1, centerY+ys, RGB(red,green,blue));
}
else
{
if (deltaY < 0)
::SetPixel(hDC, centerX-(int)xt-1, centerY+ys, RGB(red,green,blue));
else
::SetPixel(hDC, centerX+(int)xt+1, centerY+ys, RGB(red,green,blue));
}
}
oldX = (int)xt;
ys += deltaY;
}
}
}
angle += 90.0f;
startAngle = angle;
}
}
void CTGraphics::DrawPie(HDC hDC, int x1, int y1, int x2, int y2, float startAngle, float endAngle, COLORREF color)
{
int centerX = (x1 + x2) / 2;
int centerY = (y1 + y2) / 2;
int dx = (x2 - x1);
int dy = (y2 - y1);
int radiusX = (abs(dx) / 2);
int radiusY = (abs(dy) / 2);
int startX = (int)(radiusX*cos((startAngle/180.0f)*3.1415f));
int startY = (int)(radiusY*sin((startAngle/180.0f)*3.1415f));
int endX = (int)(radiusX*cos((endAngle/180.0f)*3.1415f));
int endY = (int)(radiusY*sin((endAngle/180.0f)*3.1415f));
if (endX < 0)
{
if (endY > 0)
endY++;
else
endX--;
}
else
{
if (endY < 0)
endY--;
else
endX++;
}
DrawArc(hDC, x1, y1, x2, y2, startAngle, endAngle, color);
DrawLine(hDC, centerX, centerY, centerX+startX, centerY+startY, color);
DrawLine(hDC, centerX, centerY, centerX+endX, centerY+endY, color);
}
void CTGraphics::DrawChord(HDC hDC, int x1, int y1, int x2, int y2, float startAngle, float endAngle, COLORREF color)
{
int centerX = (x1 + x2) / 2;
int centerY = (y1 + y2) / 2;
int dx = (x2 - x1);
int dy = (y2 - y1);
int radiusX = (abs(dx) / 2);
int radiusY = (abs(dy) / 2);
int startX = (int)(radiusX*cos((startAngle/180.0f)*3.1415f));
int startY = (int)(radiusY*sin((startAngle/180.0f)*3.1415f));
int endX = (int)(radiusX*cos((endAngle/180.0f)*3.1415f));
int endY = (int)(radiusY*sin((endAngle/180.0f)*3.1415f));
if (endX < 0)
{
if (endY > 0)
endY++;
else
endX--;
}
else
{
if (endY < 0)
endY--;
else
endX++;
}
DrawArc(hDC, x1, y1, x2, y2, startAngle, endAngle, color);
DrawLine(hDC, centerX+startX, centerY+startY, centerX+endX, centerY+endY, color);
}
void CTGraphics::DrawRoundRect(HDC hDC, int x1, int y1, int x2, int y2, int width, int height, COLORREF color)
{
int dx = (x2 - x1);
int dy = (y2 - y1);
int offsetX = width / 2;
width = offsetX * 2;
int offsetY = height / 2;
height = offsetY * 2;
if ((width > abs(dx)) || (height > abs(dy)))
{
DrawEllipse(hDC, x1, y1, x2, y2, color);
}
else
{
DrawLine(hDC, x1+offsetX, y1, x2-offsetX, y1, color);
DrawArc(hDC, x2-width, y1, x2, y1+height, 270.0f, 360.0f, color);
DrawLine(hDC, x2, y1+offsetY, x2, y2-offsetY, color);
DrawArc(hDC, x2-width, y2-height, x2, y2, 0.0f, 90.0f, color);
DrawLine(hDC, x2-offsetX, y2, x1+offsetX, y2, color);
DrawArc(hDC, x1, y2-height, x1+width, y2, 90.0f, 180.0f, color);
DrawLine(hDC, x1, y2-offsetY, x1, y1+offsetY, color);
DrawArc(hDC, x1, y1, x1+width, y1+height, 180.0f, 270.0f, color);
}
}
void CTGraphics::DrawBezier(HDC hDC, POINT* points, int numPoints, COLORREF color)
{
int numCurves = (numPoints-1) / 3;
int numReqPoints = numCurves*3 + 1;
if (numPoints >= numReqPoints)
{
POINT startPoint, endPoint, controlPoint1, controlPoint2;
float distance1, distance2, distance3, distanceX, distanceY;
float ax, bx, cx, ay, by, cy, t, step;
float xt, yt, k, k1;
int oldX, oldY, oldX1, oldY1;
for (int i=0; i<numCurves; i++)
{
startPoint = points[i*3];
controlPoint1 = points[i*3+1];
controlPoint2 = points[i*3+2];
endPoint = points[i*3+3];
if (controlPoint1.y == controlPoint2.y)
{
DrawLine(hDC, startPoint.x, startPoint.y, endPoint.x, endPoint.y, color);
}
else
{
distance1 = (float)sqrt(pow((double)(controlPoint1.x-startPoint.x),2) + pow((double)(controlPoint1.y-startPoint.y),2));
distance2 = (float)sqrt(pow((double)(controlPoint2.x-controlPoint1.x),2) + pow((double)(controlPoint2.y-controlPoint1.y),2));
distance3 = (float)sqrt(pow((double)(endPoint.x-controlPoint2.x),2) + pow((double)(endPoint.y-controlPoint2.y),2));
step = 1.0f / (distance1+distance2+distance3);
cx = 3.0f*(controlPoint1.x - startPoint.x);
bx = 3.0f*(controlPoint2.x - controlPoint1.x) - cx;
ax = endPoint.x - startPoint.x - bx - cx;
cy = 3.0f*(controlPoint1.y - startPoint.y);
by = 3.0f*(controlPoint2.y - controlPoint1.y) - cy;
ay = endPoint.y - startPoint.y - by - cy;
oldX = startPoint.x;
oldY = startPoint.y;
k1 = 0.0f;
for (t=0.0f; t<=1.0f; t+=step)
{
xt = ax*(t*t*t) + bx*(t*t) + cx*t + startPoint.x;
yt = ay*(t*t*t) + by*(t*t) + cy*t + startPoint.y;
distanceX = (float)(xt - (int)(xt));
distanceY = (float)(yt - (int)(yt));
if (((int)xt != oldX) && ((int)yt != oldY))
{
oldX1 = oldX;
oldY1 = oldY;
k = (float)((int)yt - oldY) / (float)((int)xt - oldX);
if (k != k1)
{
DrawLine(hDC, oldX, oldY, (int)xt, (int)yt, color);
k1 = k;
oldX = (int)xt;
oldY = (int)yt;
}
}
}
if (((int)xt != oldX1) || ((int)yt != oldY1))
{
int dx = ((int)xt - oldX1);
int dy = ((int)yt - oldY1);
if (abs(dx) > abs(dy))
{
if (dy > 0)
DrawLine(hDC, oldX, oldY, (int)xt, (int)yt+1, color);
else
DrawLine(hDC, oldX, oldY, (int)xt, (int)yt-1, color);
}
else
{
if (dx > 0)
DrawLine(hDC, oldX, oldY, (int)xt+1, (int)yt, color);
else
DrawLine(hDC, oldX, oldY, (int)xt-1, (int)yt, color);
}
}
}
}
}
}
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