Handling with dementia

[Nak]

Hi there,

I am having great fun with Pointers or Handlers or whatever you want to
call them in VB.NET. WHat I am attempting to do is create a .NET image by
using the FreeImage library. On the site they clear say,

------------------------

How do I convert a FreeImage image to a HBITMAP ?

FIBITMAP *dib = FreeImage_Load( FIF_PNG, "test.png", PNG_DEFAULT);
HBITMAP bitmap = CreateDIBitmap( hDC, FreeImage_GetIn foHeader(dib),
CBM_INIT, FreeImage_GetBi ts(dib), FreeImage_GetIn fo(dib), DIB_RGB_COLORS) ;

------------------------

Now I know that this is C++, but I thought this shouldn't be hard to
convert, surely? So I have written the following function in replacement to
the above

------------------------

Private Function getFreeImage(By Val iFileName As String) As Image
Try

'create a FreeImage Wrapper and get a handle to the desired image

Dim pFIWImage As New freeImage_Wrapp er()
Dim pIntFIHandle As Integer =
pFIWImage.FreeI mage_Load(freeI mage_Wrapper.Fr eeImage_GetFile Type(iFileName,
0), iFileName, 0)

'Create a new DC that we can use with the CreateDIBitmap API

Dim pBmpBitmap As Bitmap = New
Bitmap(Convert. ToInt32(pFIWIma ge.FreeImage_Ge tWidth(pIntFIHa ndle)),
Convert.ToInt32 (pFIWImage.Free Image_GetHeight (pIntFIHandle)) )
Dim pGraGraphics As Graphics = Graphics.FromIm age(pBmpBitmap)
Dim pIPrHDC As IntPtr = pGraGraphics.Ge tHdc


'Convert the DIB to a DDB using the API CreateDIBitmap

Dim pBIHInfoHeader As BITMAPINFOHEADE R =
pFIWImage.FreeI mage_GetInfoHea der(pIntFIHandl e)
Dim pIPrBits As IntPtr = pFIWImage.FreeI mage_GetBits(pI ntFIHandle)
Dim pBIoInfo As BITMAPINFO = pFIWImage.FreeI mage_GetInfo(pI ntFIHandle)
Dim pIntDDBHandle As Integer = CreateDIBitmap( pIPrHDC.ToInt32 ,
pBIHInfoHeader, CBM_INIT, pIPrBits, pBIoInfo, DIB_RGB_COLORS)

'Now we have a handle to a HBitmap we can create a .NET Image

Dim pImgImage As Image = Image.FromHbitm ap(New IntPtr(pIntDDBH andle))

'Release the DC and unload the image

Call pGraGraphics.Re leaseHdc(pIPrHD C)
Call pFIWImage.FreeI mage_Unload(pIn tFIHandle)

'Return out image

Return (pImgImage)
Catch ex As Exception
MessageBox.Show (ex.ToString)
Return (Nothing)
End Try
End Function

------------------------

Now all I am getting out of this is 1 black pixel, no more, no less.
Why is this? I *think* it may have something to do with the way I am
passing the handle of the HBitmap to the FromHBitmap method, according the
MSDN a handle *is* returned by the API. Unfortunately seeing as my handle
is a 32 bit integer, I can't just pass it straight to the method, so I am
creating a new IntPtr object, which I *presume* creates a pointer to my
value, or doesn't it?

I must be so close to achieving what I want, yet this bit is confusing
me, if I display the value of "New IntPtr(pIntDDBH andle)" in a messagebox I
get the same value each time, so it can't be a pointer, can it? How the
hell can I do this? I have even tried using StretchDIBits to attempt to
blit the DIB onto my bitmap but still no luck :-(

Any help would be greatly appreciated, thanks loads in advance.


Nick.

--
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
"No matter. Whatever the outcome, you are changed."

Fergus - September 5th 2003
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

[Tom Spink]

Re: Handling with dementia

Instead of getting pointers in Integers, you should recieve them in IntPtr's

You'll also need to change the parameters to IntPtr's, where appropriate.
Anything that's a handle, or a pointer, should be IntPtr.

Declare Function FreeImage_Load( ...) As IntPtr
Declare Function CreateDIBitmap( ...) As IntPtr

Dim phImage As IntPtr = CreateDIBitmap( ...)

Dim imgImage As Image = Image.FromHBitm ap(phImage)

--
HTH,
-- Tom Spink, Über Geek

Please respond to the newsgroup,
so all can benefit

" System.Reflecti on Master "

==== Converting to 2002 ====
Remove inline declarations


"Nak" <a@a.com> wrote in message
news:Oek59P0mDH A.3504@TK2MSFTN GP11.phx.gbl...[color=blue]
> Hi there,
>
> I am having great fun with Pointers or Handlers or whatever you want[/color]
to[color=blue]
> call them in VB.NET. WHat I am attempting to do is create a .NET image by
> using the FreeImage library. On the site they clear say,
>
> ------------------------
>
> How do I convert a FreeImage image to a HBITMAP ?
>
> FIBITMAP *dib = FreeImage_Load( FIF_PNG, "test.png", PNG_DEFAULT);
> HBITMAP bitmap = CreateDIBitmap( hDC, FreeImage_GetIn foHeader(dib),
> CBM_INIT, FreeImage_GetBi ts(dib), FreeImage_GetIn fo(dib),[/color]
DIB_RGB_COLORS) ;[color=blue]
>
> ------------------------
>
> Now I know that this is C++, but I thought this shouldn't be hard to
> convert, surely? So I have written the following function in replacement[/color]
to[color=blue]
> the above
>
> ------------------------
>
> Private Function getFreeImage(By Val iFileName As String) As Image
> Try
>
> 'create a FreeImage Wrapper and get a handle to the desired image
>
> Dim pFIWImage As New freeImage_Wrapp er()
> Dim pIntFIHandle As Integer =
>[/color]
pFIWImage.FreeI mage_Load(freeI mage_Wrapper.Fr eeImage_GetFile Type(iFileName,[color=blue]
> 0), iFileName, 0)
>
> 'Create a new DC that we can use with the CreateDIBitmap API
>
> Dim pBmpBitmap As Bitmap = New
> Bitmap(Convert. ToInt32(pFIWIma ge.FreeImage_Ge tWidth(pIntFIHa ndle)),
> Convert.ToInt32 (pFIWImage.Free Image_GetHeight (pIntFIHandle)) )
> Dim pGraGraphics As Graphics = Graphics.FromIm age(pBmpBitmap)
> Dim pIPrHDC As IntPtr = pGraGraphics.Ge tHdc
>
>
> 'Convert the DIB to a DDB using the API CreateDIBitmap
>
> Dim pBIHInfoHeader As BITMAPINFOHEADE R =
> pFIWImage.FreeI mage_GetInfoHea der(pIntFIHandl e)
> Dim pIPrBits As IntPtr = pFIWImage.FreeI mage_GetBits(pI ntFIHandle)
> Dim pBIoInfo As BITMAPINFO = pFIWImage.FreeI mage_GetInfo(pI ntFIHandle)
> Dim pIntDDBHandle As Integer = CreateDIBitmap( pIPrHDC.ToInt32 ,
> pBIHInfoHeader, CBM_INIT, pIPrBits, pBIoInfo, DIB_RGB_COLORS)
>
> 'Now we have a handle to a HBitmap we can create a .NET Image
>
> Dim pImgImage As Image = Image.FromHbitm ap(New IntPtr(pIntDDBH andle))
>
> 'Release the DC and unload the image
>
> Call pGraGraphics.Re leaseHdc(pIPrHD C)
> Call pFIWImage.FreeI mage_Unload(pIn tFIHandle)
>
> 'Return out image
>
> Return (pImgImage)
> Catch ex As Exception
> MessageBox.Show (ex.ToString)
> Return (Nothing)
> End Try
> End Function
>
> ------------------------
>
> Now all I am getting out of this is 1 black pixel, no more, no less.
> Why is this? I *think* it may have something to do with the way I am
> passing the handle of the HBitmap to the FromHBitmap method, according the
> MSDN a handle *is* returned by the API. Unfortunately seeing as my handle
> is a 32 bit integer, I can't just pass it straight to the method, so I am
> creating a new IntPtr object, which I *presume* creates a pointer to my
> value, or doesn't it?
>
> I must be so close to achieving what I want, yet this bit is confusing
> me, if I display the value of "New IntPtr(pIntDDBH andle)" in a messagebox[/color]
I[color=blue]
> get the same value each time, so it can't be a pointer, can it? How the
> hell can I do this? I have even tried using StretchDIBits to attempt to
> blit the DIB onto my bitmap but still no luck :-(
>
> Any help would be greatly appreciated, thanks loads in advance.
>
>
> Nick.
>
> --
>[/color]
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\[color=blue]
> "No matter. Whatever the outcome, you are changed."
>
> Fergus - September 5th 2003
>[/color]
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\[color=blue]
>
>[/color]

[Nak]

Re: Handling with dementia

Hi Tom,
[color=blue]
> Instead of getting pointers in Integers, you should recieve them in[/color]
IntPtr's[color=blue]
>
> You'll also need to change the parameters to IntPtr's, where appropriate.
> Anything that's a handle, or a pointer, should be IntPtr.
>
> Declare Function FreeImage_Load( ...) As IntPtr
> Declare Function CreateDIBitmap( ...) As IntPtr
>
> Dim phImage As IntPtr = CreateDIBitmap( ...)
>
> Dim imgImage As Image = Image.FromHBitm ap(phImage)[/color]

I've just tried as suggested but still no luck. The wrapper for the
FreeImage library I am using strictly uses Int32 rather than Intptr anyway,
I have tried using pointers but this hasn't effected it, I'm still getting 1
black pixel for any image.

This is what my function looks like at the moment,

-------------------------------------

Private Function getFreeImage(By Val iFileName As String) As Image
Try

'Create a Free Image wrapper object and then load the image,
recieving an IntPtr

Dim pFIWImage As New freeImage_Wrapp er()
Dim pIntFIHandle As IntPtr =
pFIWImage.FreeI mage_Load(freeI mage_Wrapper.Fr eeImage_GetFile Type(iFileName,
0), iFileName, 0)
Dim pBmpBitmap As Bitmap = New
Bitmap(Convert. ToInt32(pFIWIma ge.FreeImage_Ge tWidth(pIntFIHa ndle)),
Convert.ToInt32 (pFIWImage.Free Image_GetHeight (pIntFIHandle)) )

'Create a new comatible DC using the Framework, rather than Windows
API's

Dim pGraGraphics As Graphics = Graphics.FromIm age(pBmpBitmap)
Dim pIPrHDC As IntPtr = pGraGraphics.Ge tHdc

'Get the parts of the image needed to create a DDB as IntPtr's

Dim pBIHInfoHeader As IntPtr =
pFIWImage.FreeI mage_GetInfoHea der(pIntFIHandl e)
Dim pIPrBits As IntPtr = pFIWImage.FreeI mage_GetBits(pI ntFIHandle)
Dim pBIoInfo As IntPtr = pFIWImage.FreeI mage_GetInfo(pI ntFIHandle)

'Create a DDB

Dim pIntHBitmap As IntPtr = CreateDIBitmap( pIPrHDC.ToInt32 ,
pBIHInfoHeader, CBM_INIT, pIPrBits, pBIoInfo, DIB_RGB_COLORS)

'Convert into a .NET image

Dim pImgImage As Image = Image.FromHbitm ap(pIntHBitmap)

'Release the DC and unload the image

Call pGraGraphics.Re leaseHdc(pIPrHD C)
Call pFIWImage.FreeI mage_Unload(pIn tFIHandle)

'Return the .NET image

Return (pImgImage)
Catch ex As Exception
MessageBox.Show (ex.ToString)
Return (Nothing)
End Try
End Function

-------------------------------------

I'm slightly confused as to how you can actually change the signature of an
API call? I notice on MSDN with reference to CreateDIBitmap that it uses
pointers int the call, hence I am using IntPtr's in the declaration, for
example

Private Declare Function CreateDIBitmap Lib "gdi32.dll" (ByVal hdc As Int32,
ByRef lpInfoHeader As IntPtr, ByVal dwUsage As Int32, ByRef lpInitBits As
IntPtr, ByRef lpInitInfo As IntPtr, ByVal wUsage As Int32) As IntPtr

On MSDN it says that the return value is a handle to the HBitmap if
successful, I am getting a returned value every time without fail, but it is
allways the same value, if I use Err.LastDLLErro r I get code 8, not that I
know what that means exactly.

I haven't actually found any examples anywhere of CreateDIBitmap being used
in VB.NET. If this cannot be achieved in VB.NET I do not mind using C#,
after all it is only a tiny plugin that I am creating which wraps the
FreeImage library. Thanks for your help Tom, I shall keep trying different
deformations of data types.

Nick.

--
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
"No matter. Whatever the outcome, you are changed."

Fergus - September 5th 2003
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

[Nak]

Re: Handling with dementia

Hi again,

I have just made a discovery, I get the same 1 black pixel if I pass
zero pointers to the CreateDIBitmap function, so surely it must be the way
the data is being passed. I can't see that what I am doing is that wrong,
surely?

-------------------

FIBITMAP *dib = FreeImage_Load( FIF_PNG, "test.png", PNG_DEFAULT);
HBITMAP bitmap = CreateDIBitmap( hDC, FreeImage_GetIn foHeader(dib),
CBM_INIT, FreeImage_GetBi ts(dib), FreeImage_GetIn fo(dib), DIB_RGB_COLORS) ;

-------------------

Referring to the above, FIBITMAP is of Int32 type, simply aliased.
According to the C# wrapper FreeImage_GetIn foHeader returns the correct data
type for the API, so does FreeImage_GetIn fo. FreeImageGetBit s on the other
hand returns an Int32, which I *presume* is a pointer to an array, which
surely I could get to by using new IntPtr(address) ?

More deformations needed I think!

Nick.

--
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
"No matter. Whatever the outcome, you are changed."

Fergus - September 5th 2003
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

[Tom Spink]

Re: Handling with dementia

> strictly uses Int32

I don't understand, what do you mean, strictly? If the C++ function is
FIBITMAP*, then it's a pointer...

--
HTH,
-- Tom Spink, Über Geek

Please respond to the newsgroup,
so all can benefit

" System.Reflecti on Master "

==== Converting to 2002 ====
Remove inline declarations


"Nak" <a@a.com> wrote in message
news:e$Zkcz6mDH A.964@TK2MSFTNG P10.phx.gbl...[color=blue]
> Hi Tom,
>[color=green]
> > Instead of getting pointers in Integers, you should recieve them in[/color]
> IntPtr's[color=green]
> >
> > You'll also need to change the parameters to IntPtr's, where[/color][/color]
appropriate.[color=blue][color=green]
> > Anything that's a handle, or a pointer, should be IntPtr.
> >
> > Declare Function FreeImage_Load( ...) As IntPtr
> > Declare Function CreateDIBitmap( ...) As IntPtr
> >
> > Dim phImage As IntPtr = CreateDIBitmap( ...)
> >
> > Dim imgImage As Image = Image.FromHBitm ap(phImage)[/color]
>
> I've just tried as suggested but still no luck. The wrapper for the
> FreeImage library I am using strictly uses Int32 rather than Intptr[/color]
anyway,[color=blue]
> I have tried using pointers but this hasn't effected it, I'm still getting[/color]
1[color=blue]
> black pixel for any image.
>
> This is what my function looks like at the moment,
>
> -------------------------------------
>
> Private Function getFreeImage(By Val iFileName As String) As Image
> Try
>
> 'Create a Free Image wrapper object and then load the image,
> recieving an IntPtr
>
> Dim pFIWImage As New freeImage_Wrapp er()
> Dim pIntFIHandle As IntPtr =
>[/color]
pFIWImage.FreeI mage_Load(freeI mage_Wrapper.Fr eeImage_GetFile Type(iFileName,[color=blue]
> 0), iFileName, 0)
> Dim pBmpBitmap As Bitmap = New
> Bitmap(Convert. ToInt32(pFIWIma ge.FreeImage_Ge tWidth(pIntFIHa ndle)),
> Convert.ToInt32 (pFIWImage.Free Image_GetHeight (pIntFIHandle)) )
>
> 'Create a new comatible DC using the Framework, rather than[/color]
Windows[color=blue]
> API's
>
> Dim pGraGraphics As Graphics = Graphics.FromIm age(pBmpBitmap)
> Dim pIPrHDC As IntPtr = pGraGraphics.Ge tHdc
>
> 'Get the parts of the image needed to create a DDB as IntPtr's
>
> Dim pBIHInfoHeader As IntPtr =
> pFIWImage.FreeI mage_GetInfoHea der(pIntFIHandl e)
> Dim pIPrBits As IntPtr = pFIWImage.FreeI mage_GetBits(pI ntFIHandle)
> Dim pBIoInfo As IntPtr = pFIWImage.FreeI mage_GetInfo(pI ntFIHandle)
>
> 'Create a DDB
>
> Dim pIntHBitmap As IntPtr = CreateDIBitmap( pIPrHDC.ToInt32 ,
> pBIHInfoHeader, CBM_INIT, pIPrBits, pBIoInfo, DIB_RGB_COLORS)
>
> 'Convert into a .NET image
>
> Dim pImgImage As Image = Image.FromHbitm ap(pIntHBitmap)
>
> 'Release the DC and unload the image
>
> Call pGraGraphics.Re leaseHdc(pIPrHD C)
> Call pFIWImage.FreeI mage_Unload(pIn tFIHandle)
>
> 'Return the .NET image
>
> Return (pImgImage)
> Catch ex As Exception
> MessageBox.Show (ex.ToString)
> Return (Nothing)
> End Try
> End Function
>
> -------------------------------------
>
> I'm slightly confused as to how you can actually change the signature of[/color]
an[color=blue]
> API call? I notice on MSDN with reference to CreateDIBitmap that it uses
> pointers int the call, hence I am using IntPtr's in the declaration, for
> example
>
> Private Declare Function CreateDIBitmap Lib "gdi32.dll" (ByVal hdc As[/color]
Int32,[color=blue]
> ByRef lpInfoHeader As IntPtr, ByVal dwUsage As Int32, ByRef lpInitBits As
> IntPtr, ByRef lpInitInfo As IntPtr, ByVal wUsage As Int32) As IntPtr
>
> On MSDN it says that the return value is a handle to the HBitmap if
> successful, I am getting a returned value every time without fail, but it[/color]
is[color=blue]
> allways the same value, if I use Err.LastDLLErro r I get code 8, not that I
> know what that means exactly.
>
> I haven't actually found any examples anywhere of CreateDIBitmap being[/color]
used[color=blue]
> in VB.NET. If this cannot be achieved in VB.NET I do not mind using C#,
> after all it is only a tiny plugin that I am creating which wraps the
> FreeImage library. Thanks for your help Tom, I shall keep trying[/color]
different[color=blue]
> deformations of data types.
>
> Nick.
>
> --
>[/color]
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\[color=blue]
> "No matter. Whatever the outcome, you are changed."
>
> Fergus - September 5th 2003
>[/color]
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\[color=blue]
>
>[/color]

[Nak]

Re: Handling with dementia

Hi Tom,
[color=blue]
> I don't understand, what do you mean, strictly? If the C++ function is
> FIBITMAP*, then it's a pointer...[/color]

What I am saying is that the API's signature should be written correctly,
the FreeImage library returns complete classes containing the Bitmap Header
data, and not pointers too, if I go changing the signature so it returns a
pointer it isn't going to change the underlying code!!

What I need to be able to do is get the required information from the
FreeImage API's and pass a pointer to the relevant data to the API, which I
presumed was ByRef but I am not so sure if it is treated the same in C++.

I know full well that if the API description contains a * that it is a
pointer, but in VB.NET you can't just make pointers to objects, or can you?
ByRef isn't technically the same, or is it?

I have made a C# version of exactly the same thing and it still doesn't
work, it seems to me that CreateDIBitmap might not be compatible with .NET,
I haven't found one example of this FreeImage library being used in .NET nor
CreateDIBitmap. Maybe C++ .NET, that should have no problems surely?

Fun fun fun

Nick.

--
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
"No matter. Whatever the outcome, you are changed."

Fergus - September 5th 2003
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

[Nak]

Re: Handling with dementia

All working!!!

I stuck with the C# version and kept trying many different combinations, I
eventually didn't pass anything by reference and the only pointer that was
passed was for the bitmap bits.

Talk about look of shock on my face when the thing actually worked! I
thought I was flogging a dead badger with a pastrami!!

Nick.

--
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
"No matter. Whatever the outcome, you are changed."

Fergus - September 5th 2003
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

[Nak]

Re: Handling with dementia

Weyhey now working in VB.NET!

Loads of types now!

Nick.

--
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
"No matter. Whatever the outcome, you are changed."

Fergus - September 5th 2003
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\