Capture portion of PicBox

[CitizenOlek]

Hello,

I'm writing a game in VB 2005. The Game Board is a Bitmap displayed in a PictureBox within the Main Form. Occassionally I want to display a Message or a Graphic onto the Game Board, but I need a way to save and restore what was originally there. I've come across this:
<code>
Dim RectCopy As New Rectangle(X, Y, sizeX, sizeY)
<end code>
But I believe this only works to capture the Windows Form background, whereas I need to capture the PictureBox background.

[HanneSThEGreaT]

Can't you just save the background to a separate image, in other words, an in memory bitmap, then once done, revert back to that ¿
Another option would be to clone the current image ( that would make an in memory bmp ), then, once you're done, change back to it ¿

[HanneSThEGreaT]

This is what I'm talking about :
Public Class Form1
Dim bmpTemp As New Bitmap(172, 190) 'same size as picbox bmp
Dim tGrfx As Graphics = Graphics.FromImage(bmpTemp) 'graphics object
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
bmpTemp = PictureBox1.Image 'store image
PictureBox1.CreateGraphics().DrawLine(Pens.Azure, 20, 20, PictureBox1.Width - 20, 20) 'do something, in this case, draw a line
End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
PictureBox1.Image = bmpTemp 'reset picturebox pic
End Sub
End Class

Here, I'm just temporarily saving the image. After I did some processing, I changed it back.

I'm including the project with.

I hope it helps, it should ;)

[HanneSThEGreaT]

<code>
Dim RectCopy As New Rectangle(X, Y, sizeX, sizeY)
<end code>
But I believe this only works to capture the Windows Form background, whereas I need to capture the PictureBox background.

Not really. that is just creating a rectangle object. This would perhaps have been something to do with a selection rectangle. But, using this way, you'd still need to copy the part of the pciture into that rectangle, then, manipulate the rectangle independantly - similar to what I've done in Post # 2, eventhough I haven't used a rectangle ther, because you need the entire picture.

[CitizenOlek]

I am already familiar with saving and retrieving the entire Bitmap.
I thought though, that it would be more efficient and faster to merely save and retrieve the portion required. Do you think this is possible?

I am dealing with large amount of data, the PicBox is 1016 x 717.

[HanneSThEGreaT]

Oh, sorry about that, I guess I need glasses.
I tell you what, have a look at this article ( it enables you to cut out a certain area of a picture, then displays it in another box ) - you could use the same principles, as discussed in there :
http://www.codeguru.com/vb/gen/vb_graphics/gdi/article.php/c14007/

[dglienna]

I was working on something like that, and someone gave me this last night.

Public Class Form1

Dim canvas As Bitmap
Dim draggingCanvas As Bitmap

Dim g As Graphics
Dim draggingGraphics As Graphics

Dim isDragging As Boolean = False
Dim dragLoc As Point


Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'set basic properties
Me.Size = New Size(800, 600)
Me.FormBorderStyle = Windows.Forms.FormBorderStyle.Fixed3D

canvas = New Bitmap(Me.ClientSize.Width, Me.ClientSize.Height)
draggingCanvas = New Bitmap(Me.ClientSize.Width, Me.ClientSize.Height)

g = Graphics.FromImage(canvas)
draggingGraphics = Graphics.FromImage(draggingCanvas)

g.Clear(Color.Black)
draggingGraphics.Clear(Color.Black)

'Me.BackColor = Color.Black
Me.DoubleBuffered = True
MessageBox.Show("Click and drag to create rectangles.")

End Sub


Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
If e.Button = Windows.Forms.MouseButtons.Left Then
'if left button is clicked, set the dragging var to true
isDragging = True
dragLoc = e.Location
End If
End Sub

Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
If isDragging Then
draggingGraphics.DrawImageUnscaled(canvas, 0, 0)
draggingGraphics.DrawRectangle(Pens.White, IIf(e.X > dragLoc.X, dragLoc.X, e.X), IIf(e.Y > dragLoc.Y, dragLoc.Y, e.Y), Math.Abs(dragLoc.X - e.X) - 1, Math.Abs(dragLoc.Y - e.Y) - 1)
End If
Me.Refresh()
End Sub

Private Sub Form1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseUp
If e.Button = Windows.Forms.MouseButtons.Left Then
isDragging = False
draggingGraphics.DrawRectangle(Pens.DarkBlue, IIf(e.X > dragLoc.X, dragLoc.X, e.X), IIf(e.Y > dragLoc.Y, dragLoc.Y, e.Y), Math.Abs(dragLoc.X - e.X), Math.Abs(dragLoc.Y - e.Y))
draggingGraphics.FillRectangle(Brushes.Blue, IIf(e.X > dragLoc.X, dragLoc.X + 1, e.X + 1), IIf(e.Y > dragLoc.Y, dragLoc.Y + 1, e.Y + 1), Math.Abs(dragLoc.X - e.X) - 1, Math.Abs(dragLoc.Y - e.Y) - 1)
g.DrawImageUnscaled(draggingCanvas, 0, 0)
Me.Refresh()
End If

End Sub

Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
e.Graphics.DrawImageUnscaled(canvas, 0, 0)
e.Graphics.DrawImageUnscaled(draggingCanvas, 0, 0)
End Sub

End Class


You always draw the box on the backbuffer, and then copy it to the front

[CitizenOlek]

I just tried the code posted by dglienna and it works!
I used a background picture and commented out the lines:
'g.Clear(Color.Black)
'draggingGraphics.Clear(Color.Black)
and that worked too.
I'm still learning and will need to study the code to understand it.
This will definitely do what I want.

I noticed it is very slow! You can see multiply images of the dragged Box, which disappear when you stop. Is this just a limitation of VB?

[CitizenOlek]

The above code simply uses the built in Message Box.
The background is automatically restored under that.
That doesn't help in trying to capture and restore that background of a PictureBox beneath a Graphic!