//定义路径并添加一个椭圆

graphicspath gp = new graphicspath();

gp.addellipse(10, 10, 200, 100);

//用该路径定义路径梯度刷子

pathgradientbrush brush =

new pathgradientbrush(gp);

//颜色数组

color[] colors = {

color.fromargb(255, 0, 0),

color.fromargb(100, 100, 100),

color.fromargb(0, 255, 0),

color.fromargb(0, 0, 255)};

//定义颜色渐变比率

float[] r = {0.0f, 0.3f, 0.6f, 1.0f};

colorblend blend = new colorblend();

blend.colors = colors;

blend.positions = r;

brush.interpolationcolors = blend;

//在椭圆外填充一个矩形

g.fillrectangle(brush, 0, 0, 210, 110);

//用添加了椭圆的路径定义第二个路径梯度刷子

graphicspath gp2 = new graphicspath();

gp2.addellipse(300, 0, 200, 100);

pathgradientbrush brush2 = new pathgradientbrush(gp2);

//设置中心点位置和颜色

brush2.centerpoint = new pointf(450, 50);

brush2.centercolor = color.fromargb(0, 255, 0);

//设置边界颜色

color[] color2 = {color.fromargb(255, 0, 0)};

brush2.surroundcolors = color2;

//用第二个梯度刷填充椭圆

g.fillellipse(brush2, 300, 0, 200, 100);

}

gdi+的坐标系统

通用坐标系——用户自定义坐标系。

页面坐标系——虚拟坐标系。

设备坐标系——屏幕坐标系。

当页面坐标系和设备坐标系的单位都是象素时，它们相同。

private void button10_click(object sender, system.eventargs e)

{

graphics g = this.pictureboxii1.creategraphics();

g.clear(color.white);

this.draw(g);

}

private void draw(graphics g)

{

g.drawline(pens.black, 10, 10, 100, 100);

g.drawellipse(pens.black, 50, 50, 200, 100);

g.drawarc(pens.black, 100, 10, 100, 100, 20, 160);

g.drawrectangle(pens.green, 50, 200, 150, 100);

}

private void button5_click(object sender, system.eventargs e)

{

//左移

graphics g = this.pictureboxii1.creategraphics();

g.clear(color.white);

g.translatetransform(-50, 0);

this.draw(g);

}

private void button6_click(object sender, system.eventargs e)

{

//右移

graphics g = this.pictureboxii1.creategraphics();

g.clear(color.white);

g.translatetransform(50, 0);

this.draw(g);

}

private void button7_click(object sender, system.eventargs e)

{

//旋转

graphics g = this.pictureboxii1.creategraphics();

g.clear(color.white);

g.rotatetransform(-30);

this.draw(g);

}

private void button8_click(object sender, system.eventargs e)

{

//放大

graphics g = this.pictureboxii1.creategraphics();

g.clear(color.white);

g.scaletransform(1.2f, 1.2f);

this.draw(g);

}

private void button9_click(object sender, system.eventargs e)

{

//缩小

graphics g = this.pictureboxii1.creategraphics();

g.clear(color.white);

g.scaletransform(0.8f, 0.8f);

this.draw(g);

}

全局坐标——变换对于绘图表面上的每个图元都会产生影响。通常用于设定通用坐标系。

一下程序将原定移动到控件中心，并且y轴正向朝上。

//先画一个圆

graphics g = e.graphics;

g.fillrectangle(brushes.white, this.clientrectangle);

g.drawellipse(pens.black, -100, -100, 200, 200);

//使y轴正向朝上，必须做相对于x轴镜像

//变换矩阵为[1,0,0,-1,0,0]

matrix mat = new matrix(1, 0, 0, -1, 0, 0);

g.transform = mat;

rectangle rect = this.clientrectangle;

int w = rect.width;

int h = rect.height;

g.translatetransform(w/2, -h/2);

//以原点为中心，做一个半径为100的圆

g.drawellipse(pens.red, -100, -100, 200, 200);

g.translatetransform(100, 100);

g.drawellipse(pens.green, -100, -100, 200, 200);

g.scaletransform(2, 2);

g.drawellipse(pens.blue, -100, -100, 200, 200);

局部坐标系——只对某些图形进行变换，而其它图形元素不变。

protected override void onpaint(painteventargs e)

{

graphics g = e.graphics;

//客户区设置为白色

g.fillrectangle(brushes.white, this.clientrectangle);

//y轴朝上

matrix mat = new matrix(1, 0, 0, -1, 0, 0);

g.transform = mat;

//移动坐标原点到窗体中心

rectangle rect = this.clientrectangle;

int w = rect.width;

int h = rect.height;

g.translatetransform(w/2, -h/2);

//在全局坐标下绘制椭圆

g.drawellipse(pens.red, -100, -100, 200, 200);

g.fillrectangle(brushes.black, -108, 0, 8, 8);

g.fillrectangle(brushes.black, 100, 0, 8, 8);

g.fillrectangle(brushes.black, 0, 100, 8, 8);

g.fillrectangle(brushes.black, 0, -108, 8, 8);

//创建一个椭圆然后在局部坐标系中进行变换

graphicspath gp = new graphicspath();

gp.addellipse(-100, -100, 200, 200);

matrix mat2 = new matrix();

//平移

mat2.translate(150, 150);

//旋转

mat2.rotate(30);

gp.transform(mat2);

g.drawpath(pens.blue, gp);

pointf[] p = gp.pathpoints;

g.fillrectangle(brushes.black, p[0].x-2, p[0].y+2, 4, 4);

g.fillrectangle(brushes.black, p[3].x-2, p[3].y+2, 4, 4);

g.fillrectangle(brushes.black, p[6].x-4, p[6].y-4, 4, 4);

g.fillrectangle(brushes.black, p[9].x-4, p[9].y-4, 4, 4);

gp.dispose();

//base.onpaint (e);

}

alpha混合

color.fromargb()的a就是alpha。alpha的取值范围从0到255。0表示完全透明，255完全不透明。

当前色＝前景色×alpha/255+背景色×（255－alpha）/255

protected override void onpaint(painteventargs e)

{

graphics g = e.graphics;

//创建一个填充矩形

solidbrush brush = new solidbrush(color.blueviolet);

g.fillrectangle(brush, 180, 70, 200, 150);

//创建一个位图，其中两个位图之间有透明效果

bitmap bm1 = new bitmap(200, 100);

graphics bg1 = graphics.fromimage(bm1);

solidbrush redbrush =

new solidbrush(color.fromargb(210, 255, 0, 0));

solidbrush greenbrush =

new solidbrush(color.fromargb(210, 0, 255, 0));

bg1.fillrectangle(redbrush, 0, 0, 150, 70);

bg1.fillrectangle(greenbrush, 30, 30, 150, 70);

g.drawimage(bm1, 100, 100);

//创建一个位图，其中两个位图之间没有透明效果

bitmap bm2 = new bitmap(200, 100);

graphics bg2 = graphics.fromimage(bm2);

bg2.compositingmode = compositingmode.sourcecopy;

bg2.fillrectangle(redbrush, 0, 0, 150, 170);

bg2.fillrectangle(greenbrush, 30, 30, 150, 70);

g.compositingquality = compositingquality.gammacorrected;

g.drawimage(bm2, 300, 200);

//base.onpaint (e);

}

反走样

protected override void onpaint(painteventargs e)

{

graphics g = e.graphics;

//放大8倍

g.scaletransform(8, 8);

//没有反走样的图形和文字

draw(g);

//设置反走样

g.smoothingmode = smoothingmode.antialias;

//右移40

g.translatetransform(40, 0);

//再绘制就是反走样之后的了

draw(g);

//base.onpaint (e);

}

private void draw(graphics g)

{

//绘制图形和文字

g.drawline(pens.gray, 10, 10, 40, 20);

g.drawellipse(pens.gray, 20, 20, 30, 10);

string s = "反走样测试";

font font = new font("宋体", 5);

solidbrush brush = new solidbrush(color.gray);

g.drawstring(s, font, brush, 10, 40);

}

完了。暂时先总结那么多。以后发现必要的可以再补充。