How Can I Prevent Memory Leaks When Creating WPF BitmapSource from HBitmap?

Memory Leak in WPF BitmapSource Creation from HBitmap

Creating pixel-by-pixel images in WPF using CreateBitmapSourceFromHBitmap() can lead to memory leaks if not handled properly. When this method is repeatedly called without freeing the BitmapSource memory, the memory utilization continues to increase.

Underlying Cause

The issue stems from the fact that Bitmap.GetHbitmap() retrieves a handle to a GDI bitmap object. MSDN explicitly states that this handle must be freed using GDI's DeleteObject method to release the associated memory resources.

Solution

To remedy the memory leak, it is crucial to release the handle obtained from Bitmap.GetHbitmap(). The following modifications should be made:

1. Import DeleteObject from gdi32.dll: Add the necessary import statement for DeleteObject to your class-level declarations.
2. Wrap Bitmap Creation in Using Statement: Use a using statement to wrap the System.Drawing.Bitmap object to automatically dispose of the underlying resources.
3. Delete HBitmap Handle: Within the finally block of the using statement, call DeleteObject to release the GDI bitmap object's handle.

Example Code

The following code demonstrates how to use this approach:

// Import DeleteObject from gdi32.dll
[System.Runtime.InteropServices.DllImport("gdi32.dll")]
public static extern bool DeleteObject(IntPtr hObject);

// Your Code
using (System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(1000, 1000)) 
{
    // Obtain HBitmap handle
    IntPtr hBitmap = bmp.GetHbitmap(); 

    try 
    {
        // Create BitmapSource using HBitmap (using statement handles GDI bitmap disposal)
        var source = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(hBitmap, IntPtr.Zero, Int32Rect.Empty, System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions());
    }
    finally 
    {
        // Release HBitmap handle
        DeleteObject(hBitmap);
    }
}

By implementing these changes, you can effectively prevent the memory leak and correctly release the resources associated with the BitmapSource created from an HBitmap.

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