Drawing an image using XNA in VB.Net

[dday9]

A few prerequisites:

• Visual Basic.Net 2010 or higher
• Microsoft XNA 4.0 or higher

Following my prior tutorial, go ahead and add the correct XNA references and Import:

1. Microsoft.Xna.Framework
2. Microsoft.Xna.Framework.Graphics

The first thing that we will do is declare three(3) variables:

    Private grafix As Graphics.GraphicsDevice = Nothing
    Private s_Batch As SpriteBatch
    Private sprite As Texture2D

The next step in our process is to start a boolean function. Now in this function, we will try to set up the graphics device. If for whatever reason we fail, in the form_load event an error will be thrown.

    Private Function initialize(ByRef surface As PictureBox) As Boolean
        Try
            Dim pparam As New PresentationParameters
            pparam.DeviceWindowHandle = surface.Handle
            pparam.IsFullScreen = False

            Dim grafixAdapt As GraphicsAdapter = GraphicsAdapter.DefaultAdapter

            grafix = New GraphicsDevice(grafixAdapt, GraphicsProfile.HiDef, pparam)


            initialize = True
        Catch ex As Exception
            initialize = False
        End Try
    End Function

I explained what that function does in the prior tutorial. The next step is to create a function that will return a texture2d.

    Public Shared Function BitmapToTexture2D(GraphicsDevice As GraphicsDevice, image As System.Drawing.Bitmap) As Texture2D
        Dim bufferSize As Integer = image.Height * image.Width * 4

        Dim memoryStream As New System.IO.MemoryStream(bufferSize)
        image.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Png)

        memoryStream.Seek(0, SeekOrigin.Begin)
        Dim texture As Texture2D = Texture2D.FromStream(GraphicsDevice, memoryStream, image.Width, image.Height, False)
 
        memoryStream.Close()
        Return texture
    End Function

This is important because XNA isn't intended to render bitmaps, it's intended to render texture2d's. Now the main method going on in that function is the Texture2d.FromStream. Now if you aren't paying attention to the prerequisites and using a former version of XNA I believe the method used is the Texture2d.FromFile, the parameters are a bit different, but the concepts the same.

The next step is to actually convert the bitmap to a texture2d:

    Private Sub Load_Content()
        If IsNothing(grafix) = False Then
            s_Batch = New SpriteBatch(grafix)

            sprite = BitmapToTexture2D(grafix, My.Resources.my_image)
        Else
            Throw New ArgumentNullException("Grafix")
            Exit Sub
        End If

    End Sub

Finally we will use a backgroundworker to continually display our sprite:

    Private Sub BackgroundWorker1_DoWork(sender As System.Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Do Until True = False
            grafix.Clear(Color.CornflowerBlue)

            With s_Batch
                .Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend)
                .Draw(sprite, New Rectangle(0, 0, My.Resources.my_image.Width, My.Resources.my_image.Height), Color.CornflowerBlue)
                .End()
            End With

            grafix.Present()
        Loop
    End Sub

This is where all the action happens. The spritebatch.begin starts the whole process. The spritebatch.draw actually does the rendering. Finally the spritebatch.end brings the state of our device back to the state it was in before we called .Begin. You can think of spritebatch.end as FileStream.Close. The last thing we do is call graphicsdevice.Present, this actually shows the sprite. All in all in the end, it should look like this:

Option Strict On
Option Explicit On

Imports System.IO
Imports Microsoft.Xna.Framework
Imports Microsoft.Xna.Framework.Graphics
Public Class Form1
    Private grafix As Graphics.GraphicsDevice = Nothing
    Private s_Batch As SpriteBatch
    Private sprite As Texture2D

    Private Function initialize(ByRef surface As PictureBox) As Boolean
        Try
            Dim pparam As New PresentationParameters
            pparam.DeviceWindowHandle = surface.Handle
            pparam.IsFullScreen = False

            Dim grafixAdapt As GraphicsAdapter = GraphicsAdapter.DefaultAdapter

            grafix = New GraphicsDevice(grafixAdapt, GraphicsProfile.HiDef, pparam)


            initialize = True
        Catch ex As Exception
            initialize = False
        End Try
    End Function

    Public Shared Function BitmapToTexture2D(GraphicsDevice As GraphicsDevice, image As System.Drawing.Bitmap) As Texture2D
        Dim bufferSize As Integer = image.Height * image.Width * 4

        ' Create new memory stream and save image to stream so    
        ' we don't have to save and read file   
        Dim memoryStream As New System.IO.MemoryStream(bufferSize)
        image.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Png)

        ' Creates a texture from IO.Stream - our memory stream
        memoryStream.Seek(0, SeekOrigin.Begin)
        Dim texture As Texture2D = Texture2D.FromStream(GraphicsDevice, memoryStream, image.Width, image.Height, False)

        memoryStream.Close()
        Return texture
    End Function


    Private Sub Load_Content()
        If IsNothing(grafix) = False Then
            s_Batch = New SpriteBatch(grafix)

            sprite = BitmapToTexture2D(grafix, My.Resources.my_image)
        Else
            Throw New ArgumentNullException("Grafix")
            Exit Sub
        End If

    End Sub

    Private Sub BackgroundWorker1_DoWork(sender As System.Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Do Until True = False
            grafix.Clear(Color.CornflowerBlue)

            With s_Batch
                .Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend)
                .Draw(sprite, New Rectangle(0, 0, My.Resources.my_image.Width, My.Resources.my_image.Height), Color.CornflowerBlue)
                .End()
            End With

            grafix.Present()
        Loop
    End Sub

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        Dim bool As Boolean = initialize(PictureBox1)

        If bool = True Then
            Call Load_Content()

            BackgroundWorker1.RunWorkerAsync()
        Else
            MessageBox.Show("There was a problem initializing XNA.")
            Me.Close()
        End If
    End Sub
End Class

Edit - I would like to mention that the busy loop used in this example is not very relevant. Instead, you should use a game loop like the one I made here: http://www.vbforums.com/showthread.p...aged-Game-Loop

[Shaggy Hiker]

So this will draw a bitmap to the form using XNA, right? I'm wondering what the point of the backgroundworker is? I wouldn't think you'd have to be redrawing continually unless something else is drawing over your image continually, which may be the case. To draw controls with XNA I had to suppress the paint event for the control as I didn't want GDI to be painting the control when I was painting it.

[dday9]

What this does is it draw's a converted texture2d from a bitmap onto a picturebox using the 'game' loop. The reason I keep it in the backgroundworker is because of the 'game' flow concept. See in regular winform's the app assumes that everything stays the same until something is invoked, where as in game app's it assumes that everything is constantly changing. There was an article I read.... <waiting for google> .... When WinForms met the game loop that really helped me out that I think people should read when deciding when to use a 'game' loop and when to just draw in 'WinForm' fashion. So because I'm assuming that most people will visit this thread for game programming in xna I decided to keep it in a continuous loop, or the 'game' loop.

[Shaggy Hiker]

Ah, a game running in a window as opposed to a typical WinForms program that spends most of its time doing nothing.

[dday9]

Ah, a game running in a window as opposed to a typical WinForms program that spends most of its time doing nothing.

Yep, that was the flow design idea behind these series of tutorials. Something I'd like to mention to those with aspirations of XBox programming is:

A)You cannot port a vb.net xna game to XBox
B)Even if you could, you wouldn't beable to use the BitmapToTexture2D because XBox wouldn't let you.

Microsoft hasn't mentioned anything about allowing VB.Net/XNA games to be ported over to Xbox and to be honest I don't think they'll ever consider it. Reason being is because I'm assuming it would cost thousands of dollars to get Xbox to compile vb.net code.

[Shaggy Hiker]

That's kind of ironic, when you think about it. The point behind .NET, originally, was that various people would create JIT compilers for different platforms and you'd be able to take your IL and run it on different platforms. It was the idea behind JAVA, too. Therefore, it's a bit funny that MS decided not to create a JIT compiler for the only platform they totally own.

[TizzyT]

What this does is it draw's a converted texture2d from a bitmap onto a picturebox using the 'game' loop. The reason I keep it in the backgroundworker is because of the 'game' flow concept. See in regular winform's the app assumes that everything stays the same until something is invoked, where as in game app's it assumes that everything is constantly changing. There was an article I read.... <waiting for google> .... When WinForms met the game loop that really helped me out that I think people should read when deciding when to use a 'game' loop and when to just draw in 'WinForm' fashion. So because I'm assuming that most people will visit this thread for game programming in xna I decided to keep it in a continuous loop, or the 'game' loop.

I know this thread is old but...
The GameLoop should not be ran in an infinite. This is very inefficient and eats CPU. It is better to use a type of Timer instead. There are several timers you can use that are available online if you do not want to use any of the built in ones. I personally made my own Timer which is accurate to the microsecond due to there not being an efficient one built in and couldn't find an efficient one elsewhere either.

PS: You could also have done it this way instead (looks cleaner imo):
While true
...
...
End While

[dday9]

Oh yeah, trust me I don't use the infinite loop process as shown in this example any longer. I have a game loop contribution somewhere here on VBForums, but I don't know the exact link to point to off hand.

As far as a timer, I would not recommend using the System.Windows.Forms.Timer class for many reasons.

1. It is not accurate with lower level intervals like 16.6(60 FPS)
2. Resource heavy
3. Not consistent among platforms

[TizzyT]

Good to know that isn't being used anymore, and that game loop contribution should be linked imo because the information here is dated and not optimal. I don't mean The forms timer or the thread timer and of of the timers in particular but I meant a form of timer as to imply their efficiency over using an infinite while loop. Although A multimedia timer is pretty accurate down to the millisecond (the others are not real-time, the others while allowing you to set millisecond intervals they only make best efforts to do so). I would be interested in that link with the game loop so I can see what is done there and possible contribute my MicroTimer if no one has presented a good solution yet which is accurate to the micro second and is efficient for anything that doesn't loop faster than 1ms (thus 16.67 is completely doable).

As for Consistency, among platforms what do you mean by that? On linux for example the timers actually tick at the specified intervals. Or do you mean hardware wise as in a machine doesn't have a high performance counter.

[dday9]

Good to know that isn't being used anymore, and that game loop contribution should be linked imo because the information here is dated and not optimal.

I've editted the post to include game loop example.

As for Consistency, among platforms what do you mean by that? On linux for example the timers actually tick at the specified intervals. Or do you mean hardware wise as in a machine doesn't have a high performance counter.

I meant hardware wise.

[passel]

I think it is both hardware and software. Right now I can put my hands on three computers whose Timer values and Threading.Sleep values have different periods.
The Threading.Sleep in particular is a disappointment since I would like to have a short sleep (1 to 3 ms) in a background thread, but on two machines I have access to, if you do a Threading.Sleep for anything less than 15 ms, you are going to get up to 16 ms because the Threading.Sleep clock is using the 64hz clock, so will "wake up" on one of the 15.625 ms ticks of the clock, not before.

And even on the same machine, like my business laptop, if I test the period, sometimes it will be the 15.625 period, but other times be a 2 ms period, so obviously some software uses the API to set the clock tick frequency used by windows to drive some of these timers.
And while sometimes it seems like the Threading.Sleep and some timers are tied to the same clock, obviously in other cases they are not (Threading.Sleep can have a much shorter period than the timer).
There are fairly good timing sources, but not so much timer sources.

There is no consistency in Windows for the majority of the timer sources made available to the user.

[TizzyT]

Here is my MicroTimer solution I made:
http://pastebin.com/NnvJQCmK