用VB編寫畫圖程序

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編寫一個仿Windows畫圖程序〔1本例將實現(xiàn)11.1節(jié)中的一個仿Windows的簡單的畫圖軟件的任務(wù)。1．新建項目創(chuàng)建一個項目類型為VisualBasic,模板為Windows應(yīng)用程序的項目,命名為Ch11_5。2．界面設(shè)計在窗體上添加：一個MenuStrip菜單控件、一個ToolStrip工具欄控件,一個用作繪圖板的PictureBox圖片框控件、兩個讓用戶選擇顏色和線條寬標(biāo)志的Lable控件、5個讓用戶選擇線條寬度的button控件,一個Panel控件上、一個ImageList控件和一個作為狀態(tài)信息欄的StatusStripr。調(diào)整窗體上各控件的大小及位置,如圖11-18所示。

圖11-18

畫圖程序主界面3．設(shè)置各控件的相關(guān)屬性設(shè)置各控件的相關(guān)屬性,如表11-9所示。表11-9

畫圖程序各控件屬性設(shè)置

4．代碼設(shè)計〔1引入命名空間：Im〔2在FrmPaint類里定義全局變量和mSelect枚舉結(jié)構(gòu)：Private

g

As

Graphics

'繪圖句柄Private

pstart

As

Point,

pend

As

Point

'定義畫圖的起始點,終點Private

mChoice

AsInteger'選擇圖形枚舉Private

mWidth

AsInteger'畫筆寬度Private

mIcon

As

Icon

'用戶選擇圖標(biāo)PrivateEnum

mSelect

'選擇圖形類別枚舉

Pencil

'鉛筆

Line

'直線

Ellipse

'橢圓

FillEllipse

'填充橢圓

StyleEllipse

'風(fēng)格橢圓

Rec

'矩形

FillRec

'填充矩形

StyleRec

'風(fēng)格矩形

Icon

'圖標(biāo)

Eraser

'橡皮EndEnum〔3在FrmPaint的Load事件中初始化全局變量和Graphics對象：PrivateSub

FrmPaint_Load<ByVal

sender

As

System.Object,

_

ByVal

e

As

System.EventArgs>

HandlesMyBase.Load

g

=

Me.picPaint.CreateGraphics

'獲取PictureBox的繪圖句柄

mChoice

=

mSelect.Pencil

'默認(rèn)選擇選鉛筆作為繪圖工具

mWidth

=

1

'初始化畫筆寬度EndSub〔4定義轉(zhuǎn)換坐標(biāo)起點和終點的過程Convert_Point<>。轉(zhuǎn)換坐標(biāo)起始點和終點,確保起始點始終在終點的左上方,代碼如下：'確保起始點坐標(biāo)位于左上角'結(jié)束點坐標(biāo)位于右下角PrivateSub

Convert_Point<>

Dim

ptemp

As

Point

'用于交換的臨時點If

pstart.X

<

pend.X

ThenIf

pstart.Y

>

pend.Y

Then

ptemp.Y

=

pstart.Y

pstart.Y

=

pend.Y

pend.Y

=

ptemp.Y

EndIfEndIfIf

pstart.X

>

pend.X

ThenIf

pstart.Y

<

pend.Y

Then

ptemp.X

=

pstart.X

pstart.X

=

pend.X

pend.X

=

ptemp.X

EndIfIf

pstart.Y

>

pend.Y

Then

ptemp

=

pstart

pstart

=

pend

pend

=

ptemp

EndIfEndIfEndSub〔5為工具欄ItemClick事件編寫代碼：PrivateSub

tsPaint_ItemClicked<ByVal

sender

As

System.Object,

_

ByVal

e

As

System.Windows.Forms.ToolStripItem

ClickedEventArgs>

Handles

tsPaint.ItemClicked

'獲取發(fā)生事件的索引號Me.mChoice

=

Me.tsPaint.Items.IndexOf<e.ClickedItem>

If

mChoice

=

mSelect.Icon

Then'如果選擇的是圖標(biāo),則打開OpenFileDialog選取圖標(biāo)Dim

dlgOpen

AsNew

OpenFileDialog

dlgOpen.Filter

=

"圖標(biāo)文件|*.ico"If

dlgOpen.ShowDialog

=

Windows.Forms.DialogResult.OK

Then

mIcon

=

New

Icon<dlgOpen.FileName>

EndIfEndIf〔6為btnSetColor控件的Click事件,編寫代碼,選擇畫筆顏色,代碼如下：PrivateSub

btnSetColor_Click<ByVal

sender

As

System.Object,

_

ByVal

e

As

System.EventArgs>

Handles

btnSetColor.Click

'打開"顏色"對話框Dim

dlgColor

AsNew

ColorDialog

If

dlgColor.ShowDialog

=

Windows.Forms.DialogResult.OK

ThenMe.btnSetColor.BackColor

=

dlgColor.Color

EndIfEndSub〔7編寫選擇線條寬度的共享事件過程btnLines_Click<>代碼：PrivateSub

btnLine_Click<ByVal

sender

As

System.Object,

ByVal

e

As

System.EventArgs>

_

Handles

btnLine1.Click,

btnLine2.Click,

btnLine3.Click,

btnLine4.Click,

btnLine5.Click

'把所有按鈕的背景色都設(shè)為BlackMe.btnLine1.BackColor

=

Color.White

Me.btnLine2.BackColor

=

Color.White

Me.btnLine3.BackColor

=

Color.White

Me.btnLine4.BackColor

=

Color.White

Me.btnLine5.BackColor

=

Color.White

'用戶選中的按鈕背景色為BlueCType<sender,

Button>.BackColor

=

Color.Black

'把畫筆寬度設(shè)為用戶選擇按鈕的Tag值

mWidth

=

CType<sender,

Button>.Tag

EndSub〔8為PictrueBox的MouseDown〔鼠標(biāo)按下事件編寫代碼。在FrmPaint的代碼窗口頂部的"對象"下拉列表框中選擇picPaint,然后在右側(cè)的"事件"下拉列表框中選擇MouseDown,此時代碼編輯器中已經(jīng)自動生成了picPaint_MouseUp的事件代碼,并把鼠標(biāo)定位于事件過程內(nèi)部的第一行,在該過程中編寫如下代碼：PrivateSub

picPaint_MouseDown<ByVal

sender

As

System.Object,

_

ByVal

e

As

System.Windows.Forms.MouseEventArgs>

Handles

picPaint.MouseDown

If

e.Button

=

Windows.Forms.MouseButtons.Left

Then'如果用戶按下的是鼠標(biāo)左鍵,則將當(dāng)前點坐標(biāo)賦給起始點

pstart.X

=

e.X

pstart.Y

=

e.Y

EndIfEndSub11.6.2

編寫一個仿Windows畫圖程序〔3〔9為PictrueBox的MouseUp〔鼠標(biāo)釋放事件編寫代碼：PrivateSub

picPaint_MouseUp<ByVal

sender

As

System.Object,

_

ByVal

e

As

System.Windows.Forms.MouseEventArgs>

Handles

picPaint.MouseUp

If

e.Button

=

Windows.Forms.MouseButtons.Left

Then'如果用戶按下的是鼠標(biāo)左鍵,記錄終點坐標(biāo)

pend.X

=

e.X

pend.Y

=

e.Y

'根據(jù)保存的mChoice繪制圖形SelectCase

mChoice

Case

mSelect.Line

'用戶在工具欄中選擇的是鉛筆Dim

myPen

AsNew

Pen<Me.btnSetColor.BackColor,

mWidth>

g.DrawLine<myPen,

pstart,

pend>

'根據(jù)起點和終點繪制直線Case

mSelect.Rec

'用戶在工具欄中選擇的是空心矩形

Convert_Point<>

'轉(zhuǎn)換矩形的起點為其左上點Dim

myPen

AsNew

Pen<Me.btnSetColor.BackColor,

mWidth>

g.DrawRectangle<myPen,

pstart.X,

pstart.Y,

_

pend.X

-

pstart.X,

pend.Y

-

pstart.Y>

'根據(jù)起點和終點繪制空心矩形Case

mSelect.FillRec

'用戶在工具欄中選擇的是填充矩形

Convert_Point<>

'轉(zhuǎn)換矩形的起點為其左上點Dim

rec

AsNew

Rectangle<pstart.X,

pstart.Y,

_

pend.X

-

pstart.X,

pend.Y

-

pstart.Y>

'根據(jù)起點和終點定義矩形Dim

sbr

AsNew

SolidBrush<btnSetColor.

BackColor>

'定義畫刷顏色為用戶選擇的顏色

g.FillRectangle<sbr,

rec>

'繪制填充矩形Case

mSelect.StyleRec

'用戶在工具欄中選擇的是風(fēng)格矩形

Convert_Point<>

'轉(zhuǎn)換矩形的起點為其左上點Dim

rec

AsNew

Rectangle<pstart.X,

pstart.Y,

_

pend.X

-

pstart.X,

pend.Y

-

pstart.Y>

'根據(jù)起點和終點定義矩形'

定義畫刷風(fēng)格為Cross型,前景色為白色,背景色為用戶選擇Dim

hbr

AsNew

HatchBrush<HatchStyle.Cross,

Color.White,

btnSetColor.BackColor>

g.FillRectangle<hbr,

rec>

'用畫刷填充矩形Case

mSelect.Ellipse

'用戶在工具欄中選擇的是空心橢圓

Convert_Point<>

'轉(zhuǎn)換橢圓外接矩形的起點為其左上點Dim

pen1

AsNew

Pen<btnSetColor.BackColor,

mWidth>

g.DrawEllipse<pen1,

pstart.X,

pstart.Y,

_

pend.X

-

pstart.X,

pend.Y

-

pstart.Y>

'根據(jù)橢圓外接矩形的起點和終點繪制橢圓Case

mSelect.FillEllipse

'用戶在工具欄中選擇的是填充橢圓

Convert_Point<>

'轉(zhuǎn)換橢圓外接矩形的起點為其左上點Dim

rec

AsNew

Rectangle<pstart.X,

pstart.Y,

_

pend.X

-

pstart.X,

pend.Y

-

pstart.Y>

'定義橢圓的外接矩形Dim

sbr

AsNew

SolidBrush<btnSetColor.

BackColor>

'定義畫刷顏色為用戶選擇的顏色

g.FillEllipse<sbr,

rec>

'用畫刷填充矩形Case

mSelect.StyleEllipse

'用戶在工具欄中選擇的是風(fēng)格橢圓

Convert_Point<>

'轉(zhuǎn)換橢圓外接矩形的起點為其左上點Dim

rec

AsNew

Rectangle<pstart.X,

pstart.Y,

_

pend.X

-

pstart.X,

pend.Y

-

pstart.Y>

'定義橢圓的外接矩形'

定義畫刷風(fēng)格為Cross型,前景色為白色,背景色為用戶選擇Dim

hbr

AsNew

HatchBrush<HatchStyle.Cross,

Color.White,

btnSetColor.BackColor>

g.FillEllipse<hbr,

rec>

'用畫刷填充矩形EndSelectEndIfEndSub〔10為PictrueBox的MouseMove〔鼠標(biāo)移動事件編寫代碼：PrivateSub

picPaint_MouseMove<ByVal

sender

As

System.Object,

_

ByVal

e

As

System.Windows.Forms.MouseEventArgs>

Handles

picPaint.MouseMove

If

e.Button

=

Windows.Forms.MouseButtons.Left

Then'如果用戶按下的是鼠標(biāo)左鍵,根據(jù)保存的mChoice繪制圖形SelectCase

mChoice

Case

mSelect.Pencil

'用戶在工具欄中選擇的是鉛筆Dim

pen1

AsNew

Pen<btnSetColor.BackColor,

mWidth>

pend.X

=

e.X

pend.Y

=

e.Y

g.DrawLine<pen1,

pstart,

pend>

pstart

=

pend

'將已經(jīng)繪制的終點作為下一次的繪制的起點Case

mSelect.Eraser

'用戶在工具欄中選擇的是橡皮Dim

myPen

AsNew

Pen<Color.White,

mWidth>

'定義白色畫筆作為擦除效果

pend.X

=

e.X

pend.Y

=

e.Y