DIB to System.Bitmap

Introduction

This article describes a way to retrieve an image from a DIB handle to a System.Bitmap object.

I am developing a TWAIN scanning solution for my enterprise. I have developed code for scanning an image. The only problem  was that after an image is scanned, the scanned image is available in memory in DIB format and all I am having is an IntPtr pointing to the DIB image.

My purpose is to retrieve the scanned image from the DIB handle and show it in a picture box. For that, I need to convert the DIB handle into a Bitmap object. The following code shows how I solved this problem.

Using the code

Here is a code for the function BitmapFromDIB which will return you a Bitmap object from the DIB handle.

This function accepts two parameters

• pDIB: it is a pointer to a DIB which is returned after scanning an image
• pPix: it is a pointer to DIBpixels

Here, we have used the function GdipCreateBitmapFromGdiDib exported from Gdiplus.dll to get a pointer to a Bitmap. We then use reflection, and pass this pointer to the static internal method Bitmap.FromGDIplus(IntPtr pGdiBitmap).

using System.Drawing; 
using System.Reflection; // . . . 

[DllImport("GdiPlus.dll", 
   CharSet=CharSet.Unicode, ExactSpelling=true)] 
private static extern int GdipCreateBitmapFromGdiDib(IntPtr pBIH, 
                          IntPtr pPix, out IntPtr pBitmap); 


public static Bitmap BitmapFromDIB(IntPtr pDIB,IntPtr pPix) 
{ 


    MethodInfo mi = typeof(Bitmap).GetMethod("FromGDIplus", 
                    BindingFlags.Static | BindingFlags.NonPublic); 

    if (mi == null) 
        return null; // (permission problem) 

    IntPtr pBmp = IntPtr.Zero; 
    int status = GdipCreateBitmapFromGdiDib(pDIB, pPix, out pBmp); 

    if ((status == 0) && (pBmp != IntPtr.Zero)) // success 
        return (Bitmap)mi.Invoke(null, new object[] {pBmp}); 

    else 
        return null; // failure 
}