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Convert C function to VB for me

Posted on 2004-08-28
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Last Modified: 2012-06-21
I need this function to convert a graphic to a 1bpp.  Can anyone rewite this one function to VB.  I've got a little, but I'm a little lost as well.

protected unsafe  void SetIndexedPixel(int  x,int y,BitmapData bmd, bool pixel)
     {
       byte* p=(byte*)bmd.Scan0.ToPointer();
       int  index=y*bmd.Stride+(x>>3);
       byte mask=(byte)(0x80>>(x&0x7));
       if(pixel)
         p[index]|=mask;
       else
         p[index]&=(byte)(mask^0xff);
     }

My VB version wouldstart out something like:

Sub setIndexedPixel(ByVal x as Integer, ByVal y as Integer, ByRef bmd as BitmapData, ByVal pixel As Boolean)
   Dim p As IntPtr=bmd.Scan0

...and there you go - wow I suck.  Need soon.  Any takers?

Original code found at http://www.bobpowell.net/onebit.htm.
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Question by:carlajasminelewis
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Expert Comment

by:AlexFM
ID: 11925625
This code cannot be written in VB .NET. VB doesn't support unsafe programming. byte* p in C# code is not the same thing as IntPtr - this is unsafe pointer to memory region used by C# code. IntPtr is 32-bits pointer used for interoperability. Interoperability features are available both in VB and C#, while unsafe programming is available only in C#.
Compile this function to C# Dll and call it from VB .NET application.
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Expert Comment

by:gregoryyoung
ID: 11926191
also there are no shift operations in vb.net which would make this code kind of fun :) I guess you could use mult/divs by power of 2  ...

I agree with alex though, compile it in C# and add the reference to your vb app

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Expert Comment

by:dimitry_dimitry
ID: 11928868
Use BitArray and BitConverter classes for bitwise operations.
Use Marshal.Copy Method (IntPtr, Byte[], Int32, Int32) for copying from IntPtr to Byte()
Also take a look at ms-help://MS.MSDNQTR.2004JUL.1033/vbls7/html/vblrfVBSpec11_11.htm
Visual Basic Language Specification   - 11.18 Shift Operators
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by:carlajasminelewis
ID: 11931507
Alex or Greggory:
Would one of you care to compile the function as a DLL that I can call from a VB.Net program?
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Author Comment

by:carlajasminelewis
ID: 11931519
Gregory:  there are shift operators in VB
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by:gregoryyoung
ID: 11931601
sure email me ... this name at experts-exchange ill email it back.
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by:gregoryyoung
ID: 11931670
but ill need a dll with the things it references to build it
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Author Comment

by:carlajasminelewis
ID: 11931786
Really, it is only this one function.  You see, I'm trying to save a 24bpp image as a 1bpp image.  I have thermal printer that will only display 1bpp images.  It's a long story.  Someone forwarded me this link: http://www.bobpowell.net/onebit.htm .  In two functions, this guy does exactly what I need, except his is in C#.  The other function is easily migratable.

I belive the only reference it would need would be: "using System.Drawing;"

It might be worth it to take a look at the code in the link above.  It is a very simple program.
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by:gregoryyoung
ID: 11932228
ah ok

drop me an email ill send it back.
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Accepted Solution

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gregoryyoung earned 2000 total points
ID: 11932261
its built and awaiting you.

I used the namespace carlajasminelewis class is class1 unless you want something else.
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Expert Comment

by:Bob Learned
ID: 11952127
This shift operators << and >> are only in VB.NET 2003.

Bob
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by:Bob Learned
ID: 11952137
Hopefully, we will hear what the solution was, right?

Bob
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by:gregoryyoung
ID: 11952270
maybe ... I emailed it ..
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Author Comment

by:carlajasminelewis
ID: 11959217
I realized I could do that myself as well.  Thanks for all your help.
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by:gregoryyoung
ID: 11960576
this should at the least go to Bob as well.

If you like I would be happy to reopen the question.
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Expert Comment

by:Bob Learned
ID: 11962418
No, it should go to everyone that reads this question.  Emails are against E-E guidelines.

Bob
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by:gregoryyoung
ID: 11963597
the email was just the code here compiled not further info, you are the one who actually answerred the question therefor you should get the points as stated above.
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