C# GDI绘制仪表盘（纯代码实现）

纯代码实现gdi绘制仪表盘，效果在代码下面。

public partial class halfdashboarduc : usercontrol
    {
        /// <summary>
        /// 仪表盘背景图片
        /// </summary>
        private image dashboardimage;

        /// <summary>
        /// 定义该仪表盘画布的最大值为371
        /// </summary>
        private int maxsize = 371;

        /// <summary>
        /// 仪表盘画布的放大倍数，默认1
        /// </summary>
        private float multiple = 1;

        /// <summary>
        /// 定义该仪表盘的直径大小
        /// </summary>
        private float diameter;

        /// <summary>
        /// 每个间隔值
        /// </summary>
        private int intervalvalue;

        /// <summary>
        /// 仪表盘显示的最小值，默认为0
        /// </summary>
        private float minvalue = 0;

        /// <summary>
        /// 仪表盘显示的最小值
        /// </summary>
        [category("wyl")]
        [description("仪表盘显示的最小值")]
        public float minvalue
        {
            get
            {
                return minvalue;
            }
            set
            {
                if (value >= maxvalue)
                {
                    messagebox.show("最小值不能超过最大值！", "警告", messageboxbuttons.ok, messageboxicon.warning);
                    minvalue = 0;
                }
                else
                {
                    minvalue = value;
                    //drawbackimage();
                }
            }

        }

        /// <summary>
        /// 仪表盘上显示的最大值，默认123。
        /// </summary>
        private float maxvalue = 123;

        /// <summary>
        /// 仪表盘上显示的最大值
        /// </summary>
        [category("wyl")]
        [description("仪表盘上显示的最大值")]
        public float maxvalue
        {
            get
            {
                return maxvalue;
            }
            set
            {
                if (value <= minvalue)
                {
                    messagebox.show("最大值不能低于最小值！", "警告", messageboxbuttons.ok, messageboxicon.warning);
                    maxvalue = 123;
                }
                else
                {
                    maxvalue = value;
                    //drawbackimage();
                }
            }
        }

        // <summary>
        /// 仪表盘变换的值,默认为0；
        /// </summary>
        private float changevalue = 0;

        /// <summary>
        /// 仪表盘变换的值
        /// </summary>
        public float changevalue
        {
            get
            {
                return changevalue;
            }
            set
            {
                changevalue = value;
            }
        }

        /// <summary>
        /// 指针颜色
        /// </summary>
        private color pincolor = color.fromargb(191, 148, 28);

        public color pincolor
        {
            get
            {
                return pincolor;
            }
            set
            {
                pincolor = value;
            }
        }



        public halfdashboarduc()
        {
            initializecomponent();
            //双缓存防止屏幕抖动
            this.setstyle(controlstyles.optimizeddoublebuffer | controlstyles.allpaintinginwmpaint | controlstyles.doublebuffer, true);
            this.setstyle(controlstyles.userpaint, true);
            this.updatestyles();
            //设置背景颜色为透明
            this.backcolor = color.transparent;
        }

        //private int uintfontsize = 40;
        /// <summary>
        /// 初始化仪表盘画布
        /// </summary>
        private void initialcanvas()
        {
            //对比控件的长高，以最小值为仪表盘的半径
            if (this.width > 2 * this.height)
            {
                diameter = 2 * this.height - 15;
            }
            else
            {
                diameter = this.width - 15;
            }
            multiple = (float)diameter / maxsize;//计算仪表盘放大倍数
            //如果半径大于仪表盘的最大值，则设定放大倍数为默认值
            if (multiple > 1)
            {
                multiple = 1;
                diameter = maxsize;
            }
            intervalvalue = (int)((maxvalue - minvalue) / 3);//计算每个间隔之间的值
        }

        /// <summary>
        /// 画底图
        /// </summary>
        private void drawbackimage()
        {
            
            bitmap bit = new bitmap(this.width, this.height);
            graphics gp = graphics.fromimage(bit);
            gp.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
            float radius = diameter / 2;//半径
            float cerx = this.width / 2;
            float cery = this.height / 2 + radius / 2 - 10 * multiple;
            //float cery = this.height - 20 ;
            gp.translatetransform(cerx, cery);//以中心点为画布的起始点
            //gp.drawpie(new pen(new solidbrush(color.fromargb(19,20,25)),3), -radius, -radius, diameter, diameter, 175, 190);
            gp.drawarc(new pen(new solidbrush(color.fromargb(19, 20, 25)), 3), -radius, -radius, diameter, diameter, 175, 190);
            float x1 = (float)((radius) * math.cos(175 * math.pi / 180));
            float y1 = (float)((radius) * math.sin(175 * math.pi / 180));
            float x2 = (float)((radius) * math.cos(5 * math.pi / 180));
            float y2 = (float)((radius) * math.sin(5 * math.pi / 180));
            gp.drawline(new pen(new solidbrush(color.fromargb(19, 20, 25)), 3), x1, y1, x2, y2);
            
            //gp.drawellipse(new pen(brushes.red), -5, -5, 10, 10);
            float startrad = 180;//起始角度
            float sweepshot = 0;//旋转角度
            //gp.drawline(new pen(brushes.red), -radius, 0, -(radius - 10), 0);
            for (int i = 0; i <= 30; i++)
            {
                double rad = (sweepshot + startrad) * math.pi / 180;
                if (i % 5 == 0)
                {
                    float px1 = (float)((radius - 5 ) * math.cos(rad));
                    float py1 = (float)((radius - 5 ) * math.sin(rad));

                    float px2 = (float)((radius - 15) * math.cos(rad));
                    float py2 = (float)((radius - 15) * math.sin(rad));
                    gp.drawline(new pen(new solidbrush(color.fromargb(122, 179, 222)), 2), px1, py1, px2, py2);

                }
                else
                {
                    
                    float px1 = (float)((radius - 5 ) * math.cos(rad));
                    float py1 = (float)((radius - 5 ) * math.sin(rad));

                    float px2 = (float)((radius - 10 ) * math.cos(rad));
                    float py2 = (float)((radius - 10 ) * math.sin(rad));
                    gp.drawline(new pen(new solidbrush(color.fromargb(77, 88, 124)), 1), px1, py1, px2, py2);
                }
                sweepshot += 6;
            }
            //刻度字体
            font scalefont = new font("宋体", 9, fontstyle.bold);
            startrad = 270;//起始角度
            sweepshot = 0;//旋转角度
            color c1 = color.fromargb(0, 192, 0);
            for (int i = 0; i < 4; i++)
            {
                int tempvalue = i * intervalvalue;
                sizef tempsf = gp.measurestring(tempvalue.tostring(), scalefont);
                //计算角度值
                double rad = (sweepshot + startrad) * math.pi / 180;
                float px = (float)((radius - 18) * math.cos(rad));
                float py = (float)((radius - 18) * math.sin(rad));
                if (sweepshot == 0)
                {
                    gp.drawstring(tempvalue.tostring(), scalefont, brushes.wheat, px - tempsf.width / 2, py);
                }
                else if (sweepshot == 30)
                {
                    gp.drawstring(tempvalue.tostring(), scalefont, new solidbrush(c1), px - tempsf.width + 5 * multiple, py - tempsf.height / 2 + 10 * multiple);
                }
                else if (sweepshot == 60)
                {
                    gp.drawstring(tempvalue.tostring(), scalefont, new solidbrush(c1), px - tempsf.width, py - tempsf.height / 2 + 5 * multiple);
                }
                else if (sweepshot == 90)
                {
                    gp.drawstring(tempvalue.tostring(), scalefont, new solidbrush(c1), px - tempsf.width, py - tempsf.height / 2);

                }
                //else if (sweepshot == 120)
                //{
                //    gp.drawstring(tempvalue.tostring(), scalefont, new solidbrush(c1), px - tempsf.width, py - tempsf.height / 2);
                //}
                sweepshot += 30;
            }
            startrad = 270;//起始角度
            sweepshot = 0;//旋转角度
            for (int i = 0; i < 4; i++)
            {
                int tempvalue = -i * intervalvalue;
                sizef tempsf = gp.measurestring(tempvalue.tostring(), scalefont);
                //计算角度值
                double rad = (sweepshot + startrad) * math.pi / 180;
                float px = (float)((radius - 18 * multiple) * math.cos(rad));
                float py = (float)((radius - 18 * multiple) * math.sin(rad));
                if (sweepshot == -30)
                {
                    gp.drawstring(tempvalue.tostring(), scalefont, brushes.red, px, py + tempsf.height / 2);
                }
                else if (sweepshot == -60)
                {
                    gp.drawstring(tempvalue.tostring(), scalefont, brushes.red, px + tempsf.width / 2 - 10 * multiple, py + tempsf.height / 2 - 5 * multiple);
                }
                else if (sweepshot == -90)
                {
                    gp.drawstring(tempvalue.tostring(), scalefont, brushes.red, px + tempsf.width/2  , py - tempsf.height / 2);

                }
                

                sweepshot -= 30;
            }

            gp.dispose();
            this.backgroundimage = bit;
        }

        /// <summary>
        /// 画图
        /// </summary>
        /// <param name="g"></param>
        private void drawpin(graphics g)
        {
            bitmap bit = new bitmap(this.width, this.height);
            graphics gp = graphics.fromimage(bit);
            gp.smoothingmode = system.drawing.drawing2d.smoothingmode.highquality;
            float radius = diameter / 2;//半径
            float startrad = 270;//起始角度
            float sweepshot = (float)(changevalue / maxvalue * 90);//旋转角度
            float cerx = this.width / 2;
            float cery = this.height / 2 + radius / 2 - 10 * multiple;
            gp.translatetransform(cerx, cery);//以中心点为画布的起始点
            //gp.drawellipse(new pen(pincolor, 1), -5, -5, 10, 10);//画中心圆圈
            double rad = (sweepshot + startrad) * math.pi / 180;//计算角度
            float px = (float)((radius - 15) * math.cos(rad));
            float py = (float)((radius - 15) * math.sin(rad));
            pointf[] pf = new pointf[] { new pointf(0, -radius + 15), new pointf(-4, 0), new pointf(4, 0) };
            gp.rotatetransform(sweepshot);
            //pointf[] pf = new pointf[] { new pointf(px, py), new pointf(-4, 0), new pointf(4, 0) };
            gp.fillpolygon(new solidbrush(pincolor), pf);

            //gp.drawline(new pen(new solidbrush(pincolor), 3f), 0, 0, px, py);


            g.drawimage(bit, 0, 0);
            gp.dispose();
        }


        private void halfdashboarduc_load(object sender, eventargs e)
        {
            initialcanvas();
            drawbackimage();
        }

        private void halfdashboarduc_paint(object sender, painteventargs e)
        {
            drawpin(e.graphics);
        }

        private void halfdashboarduc_resize(object sender, eventargs e)
        {
            initialcanvas();
            drawbackimage();
        }
    }

效果实现如下：