[Tutorial] Bitmap images: the correct way

Today I will show you how to correctly dispose of an image, freeing it from your program and "unlocking" it to be deleted/renamed/edited/copied.

Add this above "Public Class formname"

Code:

Imports System
Imports System.IO
Imports System. Runtime.InteropServices
Imports System.Drawing
Imports System.Drawing.Imaging

Add this into a class

Code:

Imports System
Imports System. Runtime.InteropServices
Imports System.Drawing
Imports System.Drawing.Imaging


Namespace ScreenShot
    Public Class ScreenCapture

        Public Function CaptureScreen() As Image ' Capture The Screen!
'This next will return an image 
'using your desktop screen capture
            Return CaptureIt(User32.GetDesktopWindow())
        End Function

        Public Function CaptureIt(ByVal handle As IntPtr) As Image
            Dim SRCCOPY As Integer = &HCC0020
            Dim hdcSrc As IntPtr = User32.GetWindowDC(handle)
            Dim windowRect As New User32.RECT
            User32.GetWindowRect(handle, windowRect)
            Dim width As Integer = windowRect.right - windowRect.left
            Dim height As Integer = windowRect.bottom - windowRect.top
            Dim hdcDest As IntPtr = GDI32.CreateCompatibleDC(hdcSrc)
            Dim hBitmap As IntPtr = GDI32.CreateCompatibleBitmap(hdcSrc, width, height)
            Dim hOld As IntPtr = GDI32.SelectObject(hdcDest, hBitmap)
            GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, SRCCOPY)
            GDI32.SelectObject(hdcDest, hOld)
            GDI32.DeleteDC(hdcDest)
            User32.ReleaseDC(handle, hdcSrc)
            Dim img As Image = Image.FromHbitmap(hBitmap)
            GDI32.DeleteObject(hBitmap)
            Return img
        End Function

        Public Sub CaptureScreenToFile(ByVal pathPNG As String)
            Dim image As Image = CaptureScreen()
            Dim imagecopy As New Bitmap(image)
            image.Dispose()
            imagecopy.Save(pathPNG, Imaging.ImageFormat.Png)
        End Sub

        Private Class GDI32
            Public SRCCOPY As Integer = &HCC0020
            Declare Function BitBlt Lib "gdi32.dll" (ByVal hDestDC As IntPtr, ByVal x As Int32, ByVal y As Int32, ByVal nWidth As Int32, ByVal nHeight As Int32, ByVal hSrcDC As IntPtr, ByVal xSrc As Int32, ByVal ySrc As Int32, ByVal dwRop As Int32) As Int32
            Declare Function CreateCompatibleBitmap Lib "gdi32.dll" (ByVal hdc As IntPtr, ByVal nWidth As Int32, ByVal nHeight As Int32) As IntPtr
            Declare Function CreateCompatibleDC Lib "gdi32.dll" (ByVal hdc As IntPtr) As IntPtr
            Declare Function DeleteDC Lib "gdi32.dll" (ByVal hdc As IntPtr) As Int32
            Declare Function DeleteObject Lib "gdi32.dll" (ByVal hObject As IntPtr) As Int32
            Declare Function SelectObject Lib "gdi32.dll" (ByVal hdc As IntPtr, ByVal hObject As IntPtr) As IntPtr
        End Class

        Public Class User32
            <StructLayout(LayoutKind.Sequential)> Public Structure RECT
                Public left As Integer
                Public top As Integer
                Public right As Integer
                Public bottom As Integer
            End Structure

            Declare Function GetDesktopWindow Lib "user32.dll" () As IntPtr
            Declare Function GetWindowDC Lib "user32.dll" (ByVal hwnd As IntPtr) As IntPtr
            Declare Function ReleaseDC Lib "user32.dll" (ByVal hwnd As IntPtr, ByVal hdc As IntPtr) As Int32
            Declare Function GetWindowRect Lib "user32.dll" (ByVal hwnd As IntPtr, ByRef lpRect As RECT) As Int32
        End Class
    End Class
End Namespace

Then just use this as your image capturing. It will capture the entire screen and save to "C:\image.png".

Code:

Dim SCRCapture as new ScreenCapture
SCRCapture.CaptureScreenToFile("C:\image.png")

Then, if you want to delete the file later:

Code:

File.Delete("C:\image.png")

If you wanted to delete the file but used

Code:

Dim originalimage As Bitmap = CaptureScreen()
originalimage.Save("C:\image.png", Imaging.ImageFormat.Png)

it would throw an exception eventually whether after one click or two clicks of the "Delete" button (or whatever sub you have the File.Delete under).

Press thanks if this helped you at all.

@³²³

Credits for GDI32:
http://www.codeproject.com/KB/GDI-plus/BitBlt.aspx

Credits for original C# code that I cleaned up:
http://www.developerfusion.co.uk/show/4630/

Good Job ^^

Press thanks

Glad you like it.

C+P fag. No explanation ?

Gotta include credits. Obv leech is obv.

I used a gdi32 and user32 class I found somewhere and a screencapture class I also found somewhere. Reason I can't include credits is because I have no idea where those somewheres are :/

So at least say that you got the functions from somewhere I guess, otherwise people will assume you're deliberately not giving credits.

Added Credits, also the vb.net version here was buggy. So I fixed some errors.

[Tutorial] Bitmap images: the correct way

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