GDI+ ——下一代圖形設備接口

所有的圖形用戶界面(GUI)應用程序都與硬件設備（顯示器，打印機，掃描儀）進行交互，這可以表示為可讀的數據。不過應用程序並不直接和設備之間進行通信，否則必須為每台設備分別編寫 不同的用戶接口代碼。為了避免這種重復的工作，我們可以在應用程序和設備之間使用第三個組件，此組件將轉換和傳送發送到設備的數據，以及設備發送到程序的數據。而這個組件就是GDI+。GDI+是.NET Framework中與圖形設備進行交互的入口。GDI+是一組C++類，位于一個名為Gdiplus.dll的類庫中。Gdiplus.dll是Windows xp和Windows Server 2003操作系統中一個内置組件。好了，學術性的東西在這裡就不多廢唇舌了，下面我們用GDI+在Web Form中來畫一幅圖。

像類似這樣的圖想必大家都見過，當然這個圖並不標準，這裡把代碼貼出來有興趣的可以試一試！

namespace Sky_MsdnDataGrid

{

     using System;

     using System.Collections;

     using System.ComponentModel;

     using System.Data;

     using System.Drawing;

     using System.Drawing.Imaging;

     using System.Web;

     using System.Web.sessionState;

     using System.Web.UI;

     using System.Web.UI.WebControls;

     using System.Web.UI.HtmlControls;

     /// <summary>

     /// aspxChart 的摘要描述。

     /// </summary>

     public class AspxChart : System.Web.UI.Page

     {

           PRivate   Bitmap bitmap;

           private Graphics graphics;

           private    int[] arrValues;

           private string[] arrValueNames;

           private void Page_Load(object sender, System.EventArgs e)

           {

                arrValues     = new    int[6];

                arrValueNames = new string[6];

                arrValues[0]     =    100;

                arrValues[1]     =    135;

                arrValues[2]     =    115;

                arrValues[3]     =    125;

                arrValues[4]     =     75;

                arrValues[5]     =    120;

                arrValueNames[0] = "一月";

                arrValueNames[1] = "二月";

                arrValueNames[2] = "三月";

                arrValueNames[3] = "四月";

                arrValueNames[4] = "五月";

                arrValueNames[5] = "六月";

                this.Init_Bitmap();

                this.Draw_Rectangle();

                this.Draw_Pie();

                // 將繪製的圖像以 Gif 的格式保存到當前頁面響應的輸出流中

                bitmap.Save(this.Response.OutputStream,ImageFormat.Gif);

           }

           /// <summary>

           /// 對即將要被繪製的位圖(可想象為一塊畫佈)進行初始動作

           /// </summary>

           private void Init_Bitmap()

           {

                bitmap = new Bitmap(400,200);

                graphics = Graphics.FromImage(bitmap);

                graphics.Clear(Color.White);

                graphics.DrawString("X 公司上半年銷售情況",new Font("新細明体",16,FontStyle.Underline),Brushes.Black,new PointF(5,5));

           }

           #region Web Form 設計工具產生的程式碼

           override protected void OnInit(EventArgs e)

           {

                //

                // CODEGEN: 此為 asp.net Web Form 設計工具所需的呼叫。

                //

                InitializeComponent();

                base.OnInit(e);

           }

           /// <summary>

           /// 此為設計工具支援所必須的方法 - 請勿使用程式碼編輯器修改

           /// 這個方法的內容。

           /// </summary>

           private void InitializeComponent()

           {   

                this.Load += new System.EventHandler(this.Page_Load);

           }

           #endregion

           /// <summary>

           /// 在畫佈上面繪製矩形

           /// </summary>

           private void Draw_Rectangle()

           {

                int i;

                PointF symbolLeg = new PointF(335,20);

                PointF   descLeg = new PointF(360,16);

                for (i = 0; i < arrValueNames.Length; i++)

                {

                     graphics.FillRectangle(new SolidBrush(GetColor(i)),symbolLeg.X,symbolLeg.Y,20,10);

                     graphics.DrawRectangle(Pens.Black,symbolLeg.X,symbolLeg.Y,20,10);

                     graphics.DrawString(arrValueNames[i].ToString(),new Font("新細明体",8),Brushes.Black,descLeg);

                      symbolLeg.Y += 15;

                     descLeg.Y   += 16;

                }

                for (i = 0; i < arrValues.Length; i++)

                {

                     graphics.FillRectangle(new SolidBrush(GetColor(i)),(i*35) + 15,200 - arrValues[i],20,arrValues[i]);

                     graphics.DrawRectangle(Pens.Black,(i*35) + 15,200 - arrValues[i],20,arrValues[i]);

                }

           }

           /// <summary>

           /// 在畫佈上面繪製圓餅形

           /// </summary>

           private void Draw_Pie()

           {

                int i;

                // currentangle代表當前角度 totalangle代表最大角度 totalvalues代表最大的銷售額

                float sglCurrentAngle = 0,sglTotalAngle = 0,sglTotalValues = 0;

                // 計算最大銷售額

                for (i = 0; i < arrValues.Length; i++)

                     sglTotalValues += arrValues[i];

                for (i = 0; i < arrValues.Length; i++)

                {

                     // 當月角度值  ： 當月銷售額   / 最大銷售額       * 360

                     sglCurrentAngle = arrValues[i] / sglTotalValues * 360;

                     graphics.FillPie(new SolidBrush(GetColor(i)),240,95,100,100,sglTotalAngle,sglCurrentAngle);

                     graphics.DrawPie(Pens.Black,240,95,100,100,sglTotalAngle,sglCurrentAngle);

                     sglTotalAngle += sglCurrentAngle;

                }

           }

           #region Helper Function

           private Color GetColor(int itemIndex)

           {

                Color color;

                switch(itemIndex)

                {

                     case 0:

                           color = Color.Blue;

                           break;

                     case 1:

                           color = Color.Red;

                           break;

                     case 2:

                           color = Color.Yellow;

                           break;

                     case 3:

                           color = Color.Purple;

                           break;

                     case 4:

                           color = Color.Orange;

                           break;

                     case 5:

                           color = Color.Brown;

                           break;

                     default:

                           color = Color.Blue;

                           break;

                }

                return color;

           }

           #endregion

     }

}