C＃ - 将WPF Image.source转换为System.Drawing.Bitmap

Question

I've found loads of people converting a BitmapSource to a Bitmap , but what about ImageSource to Bitmap ? I am making an imaging program and I need to extract bitmaps from the image displayed in the Image element. Does anyone know how to do this?

EDIT 1:

This is a function for converting the BitmapImage to a Bitmap . Remember to set the 'unsafe' option in the compiler preferences.

public static System.Drawing.Bitmap BitmapSourceToBitmap(BitmapSource srs)
{
    System.Drawing.Bitmap btm = null;

    int width = srs.PixelWidth;

    int height = srs.PixelHeight;

    int stride = width * ((srs.Format.BitsPerPixel + 7) / 8);

    byte[] bits = new byte[height * stride];

    srs.CopyPixels(bits, stride, 0);

    unsafe
    {
        fixed (byte* pB = bits)
        {
            IntPtr ptr = new IntPtr(pB);

            btm = new System.Drawing.Bitmap(width, height, stride, System.Drawing.Imaging.PixelFormat.Format1bppIndexed, ptr);
        }
    }
    return btm;
}

Next is now to get a BitmapImage :

RenderTargetBitmap targetBitmap = new RenderTargetBitmap(
    (int)inkCanvas1.ActualWidth,
    (int)inkCanvas1.ActualHeight,
    96d, 96d,
    PixelFormats.Default);

targetBitmap.Render(inkCanvas1);

MemoryStream mse = new MemoryStream();
System.Windows.Media.Imaging.BmpBitmapEncoder mem = new BmpBitmapEncoder();
mem.Frames.Add(BitmapFrame.Create(targetBitmap));
mem.Save(mse);

mse.Position = 0;
BitmapImage bi = new BitmapImage();
bi.BeginInit();
bi.StreamSource = mse;
bi.EndInit();

Next is to convert it:

Bitmap b = new Bitmap(BitmapSourceToBitmap(bi));

Answer 1

Actually you don't need to use unsafe code. There's an overload of CopyPixels that accepts an IntPtr:

public static System.Drawing.Bitmap BitmapSourceToBitmap2(BitmapSource srs)
{
    int width = srs.PixelWidth;
    int height = srs.PixelHeight;
    int stride = width * ((srs.Format.BitsPerPixel + 7) / 8);
    IntPtr ptr = IntPtr.Zero;
    try
    {
        ptr = Marshal.AllocHGlobal(height * stride);
        srs.CopyPixels(new Int32Rect(0, 0, width, height), ptr, height * stride, stride);
        using (var btm = new System.Drawing.Bitmap(width, height, stride, System.Drawing.Imaging.PixelFormat.Format1bppIndexed, ptr))
        {
            // Clone the bitmap so that we can dispose it and
            // release the unmanaged memory at ptr
            return new System.Drawing.Bitmap(btm);
        }
    }
    finally
    {
        if (ptr != IntPtr.Zero)
            Marshal.FreeHGlobal(ptr);
    }
}

Answer 2

That example worked for me:

    public static Bitmap ConvertToBitmap(BitmapSource bitmapSource)
    {
        var width = bitmapSource.PixelWidth;
        var height = bitmapSource.PixelHeight;
        var stride = width * ((bitmapSource.Format.BitsPerPixel + 7) / 8);
        var memoryBlockPointer = Marshal.AllocHGlobal(height * stride);
        bitmapSource.CopyPixels(new Int32Rect(0, 0, width, height), memoryBlockPointer, height * stride, stride);
        var bitmap = new Bitmap(width, height, stride, PixelFormat.Format32bppPArgb, memoryBlockPointer);
        return bitmap;
    }

Answer 3

Are your ImageSource not a BitmapSource? If your loading the images from files they should be.

Reply to your comment:

Sounds like they should be BitmapSource then, BitmapSource is a subtype of ImageSource. Cast the ImageSource to BitmapSource and follow one of those blogposts.

Answer 4

You don't need a BitmapSourceToBitmap method at all. Just do the following after creating your memory stream:

mem.Position = 0;  
Bitmap b = new Bitmap(mem);