Set Custom Cursor Image Hotspot in WPF

Question

I am trying to use custom images on Cursor and I did it with these code.

public static class cursorHelper
{

    public static Cursor vertical = new Cursor(Application.GetResourceStream(getFromResource("PenCADwpf", "Images/cursors/Vertical.ico")).Stream);
    public static Cursor horizontal = new Cursor(Application.GetResourceStream(getFromResource("PenCADwpf", "Images/cursors/Horizontal.ico")).Stream);
    public static Uri getFromResource(string psAssemblyName, string psResourceName)
    {
        Uri oUri = new Uri("pack://application:,,,/" + psAssemblyName + ";component/" + psResourceName, UriKind.RelativeOrAbsolute);
        return oUri;
    }
    public static ImageSource getImageSourceFromResource(string psAssemblyName, string psResourceName)
    {
        Uri oUri = getFromResource(psAssemblyName, psResourceName);

        return BitmapFrame.Create(oUri);
    }

}

And using in code is

    private void btnVerticalMullion_Click(object sender, RoutedEventArgs e)
    {
        this.Cursor = cursorHelper.vertical;
    }

My problem is the hotspot of the Cursor is bottom-left point. I need to change it to 0,0 (top-left) point of the image. Can any body help me please? Thanks in advance,

Answer 1

It's because you are using .ICO files instead of .CUR files as the data to the Cursor class.

While the .ICO and .CUR file formats are similar, the .ICO format doesn't contain the hotspot info.

• http://en.wikipedia.org/wiki/ICO_(file_format)#cite_note-11

You have 2 choices:

• convert your .ICO files to .CUR files and embed those as resources instead
  
  Do that by using a conversion utility which you can find on the web,
  or
  create a new .CUR file in Visual Studio and then copy and paste the data from your .ICO files.

• keep them as .ICO files but hack the data so it follows the CUR format when passed to the Cursor class.

Here's some example code to modify the ICO stream to turn it into the CUR format.

In this example I tested it with an ICO file which contained a single 32X32X4bit BMP image, and I wanted the cursor to have a (15,15) hotspot.

This code is just to get you started if you go down this route...it needs more code to handle errors, and the ability to deal with ICO files that contain multiple icon images (i.e. if multiple entries), etc.

You could also use a BinaryWriter to more naturally handle the data e.g. for writing out hotspots coords that use 2 bytes (i.e. over 255) by using Write(UInt16).

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.IO;
using System.Windows.Resources;

namespace WpfApplication2
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            Uri uri = new Uri("pack://application:,,,/test.ico");

            Stream iconstream = GetCURFromICO(uri, 15, 15 );

            Cursor cursor = new Cursor(iconstream);

            this.Cursor = cursor;
        }

        public static Stream GetCursorFromICO(Uri uri, byte hotspotx, byte hotspoty)
        {
            StreamResourceInfo sri = Application.GetResourceStream(uri);

            Stream s = sri.Stream;

            byte []buffer = new byte[s.Length];

            s.Read(buffer, 0, (int)s.Length);

            MemoryStream ms = new MemoryStream();

            buffer[2] = 2; // change to CUR file type
            buffer[10] = hotspotx;
            buffer[12] = hotspoty;

            ms.Write(buffer, 0, (int)s.Length);

            ms.Position = 0;

            return ms;
        }

        public static Stream GetCURFromICOAlternativeMethod(Uri uri, byte hotspotx, byte hotspoty)
        {
            StreamResourceInfo sri = Application.GetResourceStream(uri);

            Stream s = sri.Stream;

            byte []buffer = new byte[s.Length];

            MemoryStream ms = new MemoryStream();

            ms.WriteByte(0); // always 0
            ms.WriteByte(0);
            ms.WriteByte(2); // change file type to CUR
            ms.WriteByte(0);
            ms.WriteByte(1); // 1 icon in table
            ms.WriteByte(0);

            s.Position = 6; // skip over first 6 bytes in ICO as we just wrote

            s.Read(buffer, 0, 4);
            ms.Write(buffer, 0, 4);

            ms.WriteByte(hotspotx);
            ms.WriteByte(0);

            ms.WriteByte(hotspoty);
            ms.WriteByte(0);

            s.Position += 4; // skip 4 bytes as we just wrote our own

            int remaining = (int)s.Length - 14;

            s.Read(buffer, 0, remaining);
            ms.Write(buffer, 0, remaining);

            ms.Position = 0;

            return ms;
        }
    }
}

---

<Window x:Class="WpfApplication2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>

    </Grid>
</Window>