GDI+ 画渐变色环

在onpaint() 函数中加入如下代码，本次利用DrawArc来实现。

#define PI 3.1415926

int angle=360;

int x=(rect.Width()-300)/2;

int y=190;

int width=300;

int hight=300;

int wide=34;

graphics.SetSmoothingMode(SmoothingModeAntiAlias);//抗锯齿

for(float i = 0.0; i < PI; i += (float)((float)PI/360)) {

float h,tc, tx;

float tr,tg,tb;

tr=tg=tb=1;

h = i*1.9;

tc = 1;

tx = tc * (1 - abs(fmod(h,2) - 1));

if(0 <= h && h < 1) {       tr = tc;   tg = tx;    tb = 0;   }

else if(1 <= h && h < 2) {  tr = tx;   tg = tc;    tb = 0;   }

else if(2 <= h && h < 3) {  tr = 0;    tg = tc;    tb = tx;  }

else if(3 <= h && h < 4) {  tr = 0;    tg = tx;    tb = tc;  }

else if(4 <= h && h < 5) {  tr = tx;   tg = 0;     tb = tc;  }

else if(5 <= h && h < 6) {  tr = tc;   tg = 0;     tb = tx;  }

tr = tr * 255;

tg = tg * 255;

tb = tb * 255;

Gdiplus::Pen pen(Color (255, (byte)tr, (byte)tg,(byte)tb ),wide);

angle-=1;

graphics.DrawArc(&pen, x, y, width, hight, angle ,2);

}

GDI+ 画渐变色环,布布扣,bubuko.com