ImageSearchDLL Not working with VB6.0

[dimandragos]

Hello,
can somebody help me with ImageSearchDLL to make it work ?
Here is my code :

Private Declare Function ImageSearch Lib "C:\Users\DragosPc\Desktop\sss\ImageSearchDLL.dll" _
(ByVal x1 As Integer, ByVal y1 As Integer, ByVal right As Integer, ByVal bottom As Integer, ByVal findImage As String) As String

Private Sub Command1_Click()

Dim result As String

result = ImageSearch(0, 0, 0, 0, "C:\test.bmp")

Debug.Print result


End Sub

And the Debug.Print returns a strange output:

0 1|%d|%d|%d|%d à?E´ ä³ ä³ e+000 À~PA €ÿÿGAIsProcessorFeaturePresent KERNEL32 1#QNAN 1#INF 1#IND 1#SNAN H P RSDS!›Î1äÉ÷D‡D4Š*/^ c:\imagesearchdll\release\ImageSearchDLL.pdb `D X} ¥ þÿÿÿ Ôÿÿÿ þÿÿÿ Û% ...

i search and found this thread but didn't help me
http://www.vbforums.com/showthread.p...ht=imagesearch

You can download the dll from here : http://spacefighters.rr.nu/download/ImageSearchDLL.dll


Any ideea ?

[LaVolpe]

You need to remove that DLL from you zip file. If you have a link where someone can download the DLL, then provide that instead. The rules of this forum are that you cannot upload executable files

[dimandragos]

You need to remove that DLL from you zip file. If you have a link where someone can download the DLL, then provide that instead. The rules of this forum are that you cannot upload executable files

Done, Thanks !

[LaVolpe]

Do you know if that DLL is using a stdCall or cDecl calling convention. It really matters. If you don't know, you need to try to find out. It appears your return string is corrupted & personally, leaning towards cDecl. From what I can find on the net, the return string should be no more than 50 characters. The source code for that DLL would be helpful

[LaVolpe]

Here's an idea easy enough to test. Change all 4 Integer types to Long within the function declaration. Unless the DLL is written for 16 bit O/S, likely meant to be Longs.

[Elroy]

Wow LaVolpe, do you think VB6 can make a call that uses the cDecl convention? Gosh, I wouldn't even begin to know how to manually change the stack pointer from within VB6, which would be required upon return of a call using the cDecl convention. I actually Googled just a bit and apparently there are some C "interface" DLLs but wow, what a pita.

[LaVolpe]

Wow LaVolpe, do you think VB6 can make a call that uses the cDecl convention? Gosh, I wouldn't even begin to know how to manually change the stack pointer from within VB6, which would be required upon return of a call using the cDecl convention. I actually Googled just a bit and apparently there are some C "interface" DLLs but wow, what a pita.

Yes, Paul Caton created a thunk and I've used it quite a bit for ZLIB (CDecl) calls. If interested, you can find it on PSC, search for Paul Caton Universal DLL

[Elroy]

You know, PSC has been down for the last day or two. I sure hope that's not a permanent state of affairs.

[Schmidt]

Yes, Paul Caton created a thunk and I've used it quite a bit for ZLIB (CDecl) calls. If interested, you can find it on PSC, search for Paul Caton Universal DLL

The (oleaut32.dll) DispCallFunc-API supports all kinds of different calling-conventions,
__cdecl among them, as well as COM-calls using simple VTable-Offsets, to be able to
work against COM-interfaces which are not easily reachable per VB (having no IDispatch,
or no Typelib available anywhere).

The example below includes a __cdecl-Demo against wsprintf in the C-runtime (msvcrt.dll) -
as well as a Demo, how to implement a simple COM-Interface using this technique (ITaskBarList3).

Here's the Demo: DispInvokeDemo.zip

Olaf

[LaVolpe]

The (oleaut32.dll) DispCallFunc-API supports all kinds of different calling-conventions,
__cdecl among them, as well as COM-calls using simple VTable-Offsets, to be able to
work against COM-interfaces which are not easily reachable per VB (having no IDispatch,
or no Typelib available anywhere).

The example below includes a __cdecl-Demo against wsprintf in the C-runtime (msvcrt.dll) -
as well as a Demo, how to implement a simple COM-Interface using this technique (ITaskBarList3).

Here's the Demo: DispInvokeDemo.zip

Olaf

I'm aware of that & have used it or COM objects. Don't believe the dll in question is ActiveX. FYI: Paul Caton's thunk addressed standard DLLs

[Schmidt]

I'm aware of that & have used it or COM objects.
Don't believe the dll in question is ActiveX.
FYI: Paul Caton's thunk addressed standard DLLs

You missed my point entirely (perhaps didn't even looked at the demo),
since it demonstrated calls against msvcrt.dll, which *is* a __cdecl-exporting Standard-Dll...

So the DispCallFunc-API supports not only Calls per VTable-Pointer-offsets into COM-Instances,
but also Func-Pointer-Calls against "Flat-Dlls" (__stdcall convention as well as __cdecl convention).

Olaf

[LaVolpe]

That's pretty cool. Where did you find the documentation on that function? When I last researched that API, everything I found indicated it was intended/used only for IDispatch::Invoke.

Had no idea you could pass the function pointer as the VTable parameter along with a null pUnk and it would happily call the function.

FYI: For another sample usage of that API with call made to a VB object (drag/drop DataObject), this posting shows one way of extracting dropped files from a Windows compressed folder

[dimandragos]

Vb .Net

Imports System.Runtime.InteropServices

Public Class Form1
    <DllImport("ImageSearchDLL.dll", EntryPoint:="ImageSearch")> _
    Public Shared Function ImageSearch(ByVal x1 As Integer, ByVal y1 As Integer, ByVal x2 As Integer, ByVal y2 As Integer, ByVal str As String) As String
    End Function

    Public Shared Function FindImage(ByVal bmp As String) As Integer()
        Dim x1 As Integer
        Dim y1 As Integer

        Dim Array1 As Integer() = New Integer(2) {}
        Dim strRes As String = ImageSearch(x1, y1, Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height, bmp)
        If strRes = "0" Then
            Array1(0) = 0
            Return Array1
        Else
            Dim co As String() = strRes.Split("|"c)
            Array1(0) = Integer.Parse(co(1))
            Array1(1) = Integer.Parse(co(2))
            Return Array1
        End If
    End Function

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        
        Dim Res() As Integer = FindImage("C:\test.bmp")

        If Res(0) > 0 And Res(1) > 0 Then
            MessageBox.Show("The position of the image is :" & vbNewLine & _
                "Width: " & Res(0).ToString() & vbNewLine & _
                "Height: " & Res(1).ToString())
        Else
            MessageBox.Show("Can't find image on screen !")
        End If

    End Sub

End Class

Back, i think i will finish my project in Vb .Net but if somebody can fix that code(vb6) i will be grateful.

Thank you for all your help.

LaVolpe, i like your projects on psc

[Schmidt]

Where did you find the documentation on that function? When I last researched that API, everything I found indicated it was intended/used only for IDispatch::Invoke.

Had no idea you could pass the function pointer as the VTable parameter along with a null pUnk and it would happily call the function.

You're right, the MSDN-documentation doesn't point out this behaviour or "mode" -
not sure where I read this first (a few years ago) - I think it was in a german forum...

Olaf

[Bonnie West]

... not sure where I read this first (a few years ago) - I think it was in a german forum...

@Zvoni
The DispCallFunc is basically the "generic and official Function-Caller by pointer", every VB-Dev was
always looking for (often resorting to CallWindowProc- or ASM-Hacks instead) - not sure who needs
to be given the credits for the first working VB-example (wasn't me, found it not that long ago
in a german forum the first time)... googling - ... - well, seems that the first "working VB-example"
is from 2003: http://www.activevb.de/tipps/vb6tipps/tipp0600.html


I was using Paul Catons stuff before - but since there was this nice explicit Parameter CC_STDCALL
I googled a bit more and found a whole Enum-List:

Public Enum CallingConventions
CC_FASTCALL
CC_CDECL
CC_PASCAL
CC_MACPASCAL
CC_STDCALL
CC_RESERVED
CC_SYSCALL
CC_MPWCDECL
CC_MPWPASCAL
End Enum

More googling and experimenting revealed, that the Function-Pointer is internally resolved by:
dereferencedResultOfParam_ppv + Vtbl_Offset

And (luckily) passing a Null to ppV - and the direct Function-Pointer in the Vtbl-Offset-Param,
one can do also all kind of "normal API-Calls" (not only Disp- or COM-Calls).
And in this "direct FuncPtr-Mode", the above Enum comes in very handy - and is working as
expected.

Here's a small Demo, which shows all 3 "Modes", in which DispCallFunc can be used now with
VB (StdCall-, CDECL- calls and of course also COM- (VTbl-) Calls.

http://www.vbRichClient.com/Download...InvokeDemo.zip

Olaf

[Schmidt]

Thanks Bonnie, for digging that out.
(was aware that I've posted the info somewhere recently, but not that it was here in this Forum) ...

The blessings of getting old(er) perhaps.

Olaf