create an empty BitmapSource in C#

Thanks to Arcutus hint I have this now (wich works fine):

var i = BitmapImage.Create(
    2,
    2,
    96,
    96,
    PixelFormats.Indexed1,
    new BitmapPalette(new List<Color> { Colors.Transparent }),
    new byte[] { 0, 0, 0, 0 },
    1);

If I make this image smaller I get an ArgumentException. I have no clue why I can't create a smaller image that 2x2px.

Use the Create method.

Example stolen from MSDN: :)

int width = 128;
int height = width;
int stride = width/8;
byte[] pixels = new byte[height*stride];

// Try creating a new image with a custom palette.
List<System.Windows.Media.Color> colors = new List<System.Windows.Media.Color>();
colors.Add(System.Windows.Media.Colors.Red);
colors.Add(System.Windows.Media.Colors.Blue);
colors.Add(System.Windows.Media.Colors.Green);
BitmapPalette myPalette = new BitmapPalette(colors);

// Creates a new empty image with the pre-defined palette
BitmapSource image = BitmapSource.Create(
                                         width, height,
                                         96, 96,
                                         PixelFormats.Indexed1,
                                         myPalette, 
                                         pixels, 
                                         stride);

The way to create such an image without allocating a big managed byte array is to use TransformedBitmap.

var bmptmp = BitmapSource.Create(1,1,96,96,PixelFormats.Bgr24,null,new byte[3]{0,0,0},3);

var imgcreated = new TransformedBitmap(bmptmp, new ScaleTransform(width, height));