Add a UAC shield to a button and retain its background image?

Question

Using C# and .Net 4.0 in a winforms application: Is it possible to add the UAC shield to a button and retain the buttons background image? How?

This is what I'm using at the moment, but it removes the image...

[DllImport("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, uint Msg, int wParam, int lParam);

public static void UACToButton(Button button, bool add)
{
    const Int32 BCM_SETSHIELD = 0x160C;
    if (add)
        {
        // The button must have the flat style
        button.FlatStyle = FlatStyle.System;
        if (button.Text == "")
        // and it must have text to display the shield
            button.Text = " ";
            SendMessage(button.Handle, BCM_SETSHIELD, 0, 1);        
        }
        else
            SendMessage(button.Handle, BCM_SETSHIELD, 0, 0);    
}

Thanks!

Livraison

Are you trying to only display the shield without text on the button? – Bergamo

The button has no text. It only has an image, which is removed when the method is called. – Livraison

Load the icon from imageres.dll and draw it on your own over the background image before drawing the image on the button. – Enid

Answer 1

As Elmue mentioned, SystemIcons.Shield is the easiest way to access the UAC Shield icon. Here's the method that I use to add it on top of other images:

public static Image AddUACShieldToImage(Image image)
    {
        var shield = SystemIcons.Shield.ToBitmap();
        shield.MakeTransparent();

        var g = Graphics.FromImage(image);
        g.CompositingMode = CompositingMode.SourceOver;
        g.DrawImage(shield, new Rectangle(image.Width / 2, image.Height / 2, image.Width / 2, image.Height / 2));

        return image;
    }

Pedrick

Answer 2

Perhaps this will help: http://blog.csharphelper.com/2011/03/03/add-uac-shields-to-buttons-menu-items-and-picture-boxes-in-c.aspx

It takes the UAC shield and returns a bitmap that can be placed on anything that supports bitmaps.

EDIT: Here's some rough sample code that could work:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace UAC_Test
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        [DllImport("user32.dll")]
        public static extern int SendMessage(IntPtr hWnd, uint Msg, int wParam, int lParam);

        // Make the button display the UAC shield.
        public static void AddShieldToButton(Button btn)
        {
            const Int32 BCM_SETSHIELD = 0x160C;

            // Give the button the flat style and make it display the UAC shield.
            btn.FlatStyle = System.Windows.Forms.FlatStyle.System;
            SendMessage(btn.Handle, BCM_SETSHIELD, 0, 1);
        }

        // Return a bitmap containing the UAC shield.
        private static Bitmap shield_bm = null;
        public static Bitmap GetUacShieldImage()
        {
            if (shield_bm != null) return shield_bm;

            const int WID = 50;
            const int HGT = 50;
            const int MARGIN = 4;

            // Make the button. For some reason, it must
            // have text or the UAC shield won't appear.
            Button btn = new Button();
            btn.Text = " ";
            btn.Size = new Size(WID, HGT);
            AddShieldToButton(btn);

            // Draw the button onto a bitmap.
            Bitmap bm = new Bitmap(WID, HGT);
            btn.Refresh();
            btn.DrawToBitmap(bm, new Rectangle(0, 0, WID, HGT));

            // Find the part containing the shield.
            int min_x = WID, max_x = 0, min_y = HGT, max_y = 0;

            // Fill on the left.
            for (int y = MARGIN; y < HGT - MARGIN; y++)
            {
                // Get the leftmost pixel's color.
                Color target_color = bm.GetPixel(MARGIN, y);

                // Fill in with this color as long as we see the target.
                for (int x = MARGIN; x < WID - MARGIN; x++)
                {
                    // See if this pixel is part of the shield.
                    if (bm.GetPixel(x, y).Equals(target_color))
                    {
                        // It's not part of the shield.
                        // Clear the pixel.
                        bm.SetPixel(x, y, Color.Transparent);
                    }
                    else
                    {
                        // It's part of the shield.
                        if (min_y > y) min_y = y;
                        if (min_x > x) min_x = x;
                        if (max_y < y) max_y = y;
                        if (max_x < x) max_x = x;
                    }
                }
            }

            // Clip out the shield part.
            int shield_wid = max_x - min_x + 1;
            int shield_hgt = max_y - min_y + 1;
            shield_bm = new Bitmap(shield_wid, shield_hgt);
            Graphics shield_gr = Graphics.FromImage(shield_bm);
            shield_gr.DrawImage(bm, 0, 0,
                new Rectangle(min_x, min_y, shield_wid, shield_hgt),
                GraphicsUnit.Pixel);

            // Return the shield.
            return shield_bm;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            Graphics gfx = Graphics.FromImage(button1.BackgroundImage);
            Bitmap shield = GetUacShieldImage();
            gfx.DrawImage(shield, button1.Width / 2, button1.Height / 2);
        }
    }
}

This is drawing the UAC shield over the background image. You can adjust the image location on top of the button. It doesn't look as pretty as the System UAC shield, but it does show the UAC shield icon on top of your background image.

Bergamo

No. It gets the UAC shield as a bitmap and puts that on anything that supports bitmaps. Take that code and add a background image to the button and you'll see my problem. But thanks anyway. – Livraison

I've updated my answer to include some sample code. I forgot to mention initially that you'll need to draw the UAC shield over your background image. – Bergamo

This is horribly complicated! Use SystemIcons.Shield if supported by your framework or load it from imageres.dll or download that icon from elsewhere and draw it on your own. – Enid