public static IntPtr GenerateHICON(ImageSource image, Size dimensions)
{
if (image == null)
{
return(IntPtr.Zero);
}
// If we're getting this from a ".ico" resource, then it comes through as a BitmapFrame.
// We can use leverage this as a shortcut to get the right 16x16 representation
// because DrawImage doesn't do that for us.
var bf = image as BitmapFrame;
if (bf != null)
{
bf = GetBestMatch(bf.Decoder.Frames, (int)dimensions.Width, (int)dimensions.Height);
}
else
{
// Constrain the dimensions based on the aspect ratio.
var drawingDimensions = new Rect(0, 0, dimensions.Width, dimensions.Height);
// There's no reason to assume that the requested image dimensions are square.
double renderRatio = dimensions.Width / dimensions.Height;
double aspectRatio = image.Width / image.Height;
// If it's smaller than the requested size, then place it in the middle and pad the image.
if (image.Width <= dimensions.Width && image.Height <= dimensions.Height)
{
drawingDimensions = new Rect((dimensions.Width - image.Width) / 2, (dimensions.Height - image.Height) / 2, image.Width, image.Height);
}
else if (renderRatio > aspectRatio)
{
double scaledRenderWidth = (image.Width / image.Height) * dimensions.Width;
drawingDimensions = new Rect((dimensions.Width - scaledRenderWidth) / 2, 0, scaledRenderWidth, dimensions.Height);
}
else if (renderRatio < aspectRatio)
{
double scaledRenderHeight = (image.Height / image.Width) * dimensions.Height;
drawingDimensions = new Rect(0, (dimensions.Height - scaledRenderHeight) / 2, dimensions.Width, scaledRenderHeight);
}
var dv = new DrawingVisual();
DrawingContext dc = dv.RenderOpen();
dc.DrawImage(image, drawingDimensions);
dc.Close();
var bmp = new RenderTargetBitmap((int)dimensions.Width, (int)dimensions.Height, 96, 96, PixelFormats.Pbgra32);
bmp.Render(dv);
bf = BitmapFrame.Create(bmp);
}
// Using GDI+ to convert to an HICON.
// I'd rather not duplicate their code.
using (MemoryStream memstm = new MemoryStream())
{
BitmapEncoder enc = new PngBitmapEncoder();
enc.Frames.Add(bf);
enc.Save(memstm);
using (var istm = new ManagedIStream(memstm))
{
// We are not bubbling out GDI+ errors when creating the native image fails.
IntPtr bitmap = IntPtr.Zero;
try
{
Status gpStatus = NativeMethodsShell.GdipCreateBitmapFromStream(istm, out bitmap);
if (Status.Ok != gpStatus)
{
return(IntPtr.Zero);
}
IntPtr hicon;
gpStatus = NativeMethodsShell.GdipCreateHICONFromBitmap(bitmap, out hicon);
if (Status.Ok != gpStatus)
{
return(IntPtr.Zero);
}
// Caller is responsible for freeing this.
return(hicon);
}
finally
{
Utility.SafeDisposeImage(ref bitmap);
}
}
}
}
