Problems with Bitblt/Memory

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EDN Admin

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The below code works with some programs like the calculator but not with other programs. Here is the problem:
1) I save the Window Image to the Desktop
2) When I try to save an updated Image of that same Window to the Desktop it saves the initial Image only and not the updated one
This problem happens each time I reopen the program I am trying to obtain the image from.
Why would this program happen to some windows but not others?


<div style="color:Black;background-color:White; <pre>
<span style="color:Blue; Imports System.Runtime.InteropServices
<span style="color:Blue; Imports System.Diagnostics
<span style="color:Blue; Imports System.Runtime.CompilerServices
<span style="color:Blue; Imports System.Drawing
<span style="color:Blue; Imports System.Windows.Forms

<span style="color:Blue; Public <span style="color:Blue; Class Form1

<span style="color:Blue; Private <span style="color:Blue; Declare <span style="color:Blue; Function FindWindow <span style="color:Blue; Lib <span style="color:#A31515; "user32" <span style="color:Blue; Alias <span style="color:#A31515; "FindWindowA" (<span style="color:Blue; ByVal lpClassName <span style="color:Blue; As <span style="color:Blue; String, <span style="color:Blue; ByVal lpWindowName <span style="color:Blue; As <span style="color:Blue; String) <span style="color:Blue; As <span style="color:Blue; Integer
<span style="color:Blue; Private <span style="color:Blue; Declare <span style="color:Blue; Function SetForegroundWindow <span style="color:Blue; Lib <span style="color:#A31515; "user32" <span style="color:Blue; Alias <span style="color:#A31515; "SetForegroundWindow" (<span style="color:Blue; ByVal hWnd <span style="color:Blue; As <span style="color:Blue; Integer) <span style="color:Blue; As <span style="color:Blue; Integer
<span style="color:Blue; Private <span style="color:Blue; Declare <span style="color:Blue; Function GetWindowRect <span style="color:Blue; Lib <span style="color:#A31515; "user32" (<span style="color:Blue; ByVal hwnd <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByRef lpRect <span style="color:Blue; As RECT) <span style="color:Blue; As <span style="color:Blue; Integer
<span style="color:Blue; Private <span style="color:Blue; Declare <span style="color:Blue; Function GetWindowDC <span style="color:Blue; Lib <span style="color:#A31515; "user32" (<span style="color:Blue; ByVal hwnd <span style="color:Blue; As <span style="color:Blue; Integer) <span style="color:Blue; As <span style="color:Blue; Integer
<span style="color:Blue; Private <span style="color:Blue; Declare <span style="color:Blue; Function BitBlt <span style="color:Blue; Lib <span style="color:#A31515; "gdi32" (<span style="color:Blue; ByVal hDestDC <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByVal x <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByVal y <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByVal nWidth <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByVal nHeight <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByVal hSrcDC <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByVal xSrc <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByVal ySrc <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByVal dwRop <span style="color:Blue; As <span style="color:Blue; Integer) <span style="color:Blue; As <span style="color:Blue; Integer
<span style="color:Blue; Private <span style="color:Blue; Declare <span style="color:Blue; Function DeleteDC <span style="color:Blue; Lib <span style="color:#A31515; "GDI32" (<span style="color:Blue; ByVal hDC <span style="color:Blue; As <span style="color:Blue; Integer) <span style="color:Blue; As <span style="color:Blue; Long
<span style="color:Blue; Private <span style="color:Blue; Declare <span style="color:Blue; Function ReleaseDC <span style="color:Blue; Lib <span style="color:#A31515; "user32" (<span style="color:Blue; ByVal hwnd <span style="color:Blue; As <span style="color:Blue; Integer, <span style="color:Blue; ByVal hdc <span style="color:Blue; As <span style="color:Blue; Integer) <span style="color:Blue; As <span style="color:Blue; Integer

<span style="color:Blue; Private <span style="color:Blue; Const SRCCOPY = &HCC0020

<span style="color:Blue; Private <span style="color:Blue; Structure RECT
<span style="color:Blue; Dim Left <span style="color:Blue; As <span style="color:Blue; Integer
<span style="color:Blue; Dim Top <span style="color:Blue; As <span style="color:Blue; Integer
<span style="color:Blue; Dim Right <span style="color:Blue; As <span style="color:Blue; Integer
<span style="color:Blue; Dim Bottom <span style="color:Blue; As <span style="color:Blue; Integer
<span style="color:Blue; End <span style="color:Blue; Structure

<span style="color:Blue; Private <span style="color:Blue; Sub Button1_Click(<span style="color:Blue; ByVal sender <span style="color:Blue; As System.Object, <span style="color:Blue; ByVal e <span style="color:Blue; As System.EventArgs) <span style="color:Blue; Handles Button1.Click
<span style="color:Blue; Dim hWnd <span style="color:Blue; As <span style="color:Blue; Long
<span style="color:Blue; Dim gr1 <span style="color:Blue; As Graphics
<span style="color:Blue; Dim dc1 <span style="color:Blue; As IntPtr
<span style="color:Blue; Dim dc2 <span style="color:Blue; As <span style="color:Blue; Long
<span style="color:Blue; Dim r <span style="color:Blue; As <span style="color:Blue; Long = 0
<span style="color:Blue; Dim Rec <span style="color:Blue; As RECT

<span style="color:Green; Obtain Window Handle
hWnd = FindWindow(vbNullString, <span style="color:#A31515; "Calculator")

<span style="color:Green; Bring Window to the Top
SetForegroundWindow(hWnd)

<span style="color:Green; Get Window Dimentions
GetWindowRect(hWnd, Rec)

<span style="color:Green; New Bitmap
<span style="color:Blue; Dim Window_Image <span style="color:Blue; As <span style="color:Blue; New Bitmap(Rec.Right - Rec.Left, Rec.Bottom - Rec.Top)

<span style="color:Green; Get the graphics object for the bitmap
gr1 = Graphics.FromImage(Window_Image)

<span style="color:Green; Get the device Context from the graphics object
dc1 = gr1.GetHdc()

<span style="color:Green; Get the DC of the Window
dc2 = GetWindowDC(hWnd)

<span style="color:Green; Copy the other windows DC into the one we created
BitBlt(dc1, 0, 0, Rec.Right - Rec.Left, Rec.Bottom - Rec.Top, dc2, 0, 0, SRCCOPY)

<span style="color:Green; Clean up
r = DeleteDC(dc1)
r = ReleaseDC(hWnd, dc2)
gr1.ReleaseHdc(dc1)

<span style="color:Green; Save the picture as a bitmap to the Desktop
Window_Image.Save(<span style="color:#A31515; "C:DesktopPic.bmp", System.Drawing.Imaging.ImageFormat.Bmp)

<span style="color:Blue; End
<span style="color:Blue; End <span style="color:Blue; Sub

<span style="color:Blue; End <span style="color:Blue; Class
[/code]
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