Paint Application in Visual F#

The following example demonstrates how to make a simple Paint-like application in Visual F#:

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1. // Learn more about F# at http://fsharp.net  
2. //specifies the memory location of the class files  
3. //that will be needed in our application  
4. open System.Collections.Generic  
5. open System  
6. open System.Windows.Forms  
7. open System.ComponentModel  
8. open System.Drawing  
9. open System.Drawing.Drawing2D  
10. let drawingform = new Form(Text="Draw Objects",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)  
11. //creates our control  
12. let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))  
13. let erasebutton=new Button(Text="Erase", Location=new System.Drawing.Point(120, 200))  
14. let colorbutton=new Button(Text="Brush Color", Location=new System.Drawing.Point(40, 200))  
15. drawingform.Controls.Add(exitbutton)  
16. drawingform.Controls.Add(erasebutton)  
17. drawingform.Controls.Add(colorbutton)  
18. //creates a color dialog box  
19. let colordlg=new ColorDialog()  
20. //creates a colorblend object  
21. let mutable color=new ColorBlend()  
22.   
23. let gr=drawingform.CreateGraphics()  
24. gr.SmoothingMode<-SmoothingMode.HighQuality  
25. //when the form is loaded, change its color to white  
26. drawingform.Load.Add(fun background->  
27. //set the default brush color to indigo  
28. color.Colors<-[|Color.Indigo|]  
29.                         drawingform.BackColor<-Color.White)  
30.   
31. drawingform.MouseMove.Add(fun trail->  
32. //when the mouse button is moved and the left button is clicked  
33.   
34. if (trail.Button=System.Windows.Forms.MouseButtons.Left)then  
35. //draw the object assign the color seleted from the color dialog as a brush color  
36. gr.FillRectangle(new SolidBrush(color.Colors.[0]),new Rectangle(trail.X,trail.Y,5,5)))   
37. //when the erase button is clicked  
38. //erase the object drawn in the form  
39. erasebutton.Click.Add(fun erase->gr.Clear(Color.White))   
40. //when the exit button is clicked  
41. //quit the form                                                                                                                
42. exitbutton.Click.Add(fun quit->drawingform.Close())  
43. //when the brush color button is selected                                                            
44. colorbutton.Click.Add(fun colors->  
45. //display the Color Dialog box  
46. if colordlg.ShowDialog()=DialogResult.OK then  
47. //store the value selected by the user in our colorblend object  
48. color.Colors<-[|colordlg.Color|])  
49. //executes our application  
50. Application.Run(drawingform)  

// Learn more about F# at http://fsharp.net
//specifies the memory location of the class files
//that will be needed in our application
open System.Collections.Generic
open System
open System.Windows.Forms
open System.ComponentModel
open System.Drawing
open System.Drawing.Drawing2D
let drawingform = new Form(Text="Draw Objects",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)
//creates our control
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
let erasebutton=new Button(Text="Erase", Location=new System.Drawing.Point(120, 200))
let colorbutton=new Button(Text="Brush Color", Location=new System.Drawing.Point(40, 200))
drawingform.Controls.Add(exitbutton)
drawingform.Controls.Add(erasebutton)
drawingform.Controls.Add(colorbutton)
//creates a color dialog box
let colordlg=new ColorDialog()
//creates a colorblend object
let mutable color=new ColorBlend()

let gr=drawingform.CreateGraphics()
gr.SmoothingMode<-SmoothingMode.HighQuality
//when the form is loaded, change its color to white
drawingform.Load.Add(fun background->
//set the default brush color to indigo
color.Colors<-[|Color.Indigo|]
                        drawingform.BackColor<-Color.White)

drawingform.MouseMove.Add(fun trail->
//when the mouse button is moved and the left button is clicked

if (trail.Button=System.Windows.Forms.MouseButtons.Left)then
//draw the object assign the color seleted from the color dialog as a brush color
gr.FillRectangle(new SolidBrush(color.Colors.[0]),new Rectangle(trail.X,trail.Y,5,5))) 
//when the erase button is clicked
//erase the object drawn in the form
erasebutton.Click.Add(fun erase->gr.Clear(Color.White)) 
//when the exit button is clicked
//quit the form                                                                                                              
exitbutton.Click.Add(fun quit->drawingform.Close())
//when the brush color button is selected                                                          
colorbutton.Click.Add(fun colors->
//display the Color Dialog box
if colordlg.ShowDialog()=DialogResult.OK then
//store the value selected by the user in our colorblend object
color.Colors<-[|colordlg.Color|])
//executes our application
Application.Run(drawingform)

Click the run icon once you are done entering these codes in the code editor window. You should see the following outputs: