Question

I have a bitmap that contains 24×24 icons. I would like to use it in an image list for a toolstrip. Is it possible to use the bitmap and select the right portion of it based on the ImageIndex of a ToolStripButton? I would like to avoid splitting it into multiple files.

Answer 1

You could inherit ToolStripButton and provide a new source for the image. Here is a fairly simplistic approach; you might need to expand upon the idea for your exact needs.

    public class ToolStripImageButton: ToolStripButton
{
    public ToolStripImageButton()
        : base()
    {
    }


    private Image iconMap;
    private Int32 iconMapIndex;

    [RefreshProperties(System.ComponentModel.RefreshProperties.Repaint)]
    public Image IconMap
    {
        get { return this.iconMap; }
        set
        {
            this.iconMap = value;
            this.RecalculateImage();
        }
    }
    [RefreshProperties(System.ComponentModel.RefreshProperties.Repaint)]
    public Int32 IconMapIndex
    {
        get { return this.iconMapIndex; }
        set
        {
            this.iconMapIndex = value;
            this.RecalculateImage();
        }
    }

    protected void RecalculateImage()
    {
        if (base.Image != null)
        {
            base.Image.Dispose();
            base.Image = null;
        }
        if (this.iconMap != null)
        {
            // assumes each icon is 16x16, you could add more properties for flexibility
            Int32 x = this.iconMap.Width / 16;
            Int32 y = this.iconMap.Width / 16;

            Int32 iconCount = x * y;
            if (this.iconMapIndex < 0 || this.iconMapIndex >= iconCount) return;

            Int32 offsetX = (this.iconMapIndex % x) * 16;
            Int32 offsetY = (this.iconMapIndex / x) * 16;

            Bitmap bitmap = new Bitmap(16, 16);
            using (Graphics g = Graphics.FromImage(bitmap))

            g.DrawImage(
                this.iconMap,
                new Rectangle(0,0,bitmap.Width,bitmap.Height), 
                new Rectangle(offsetX, offsetY, bitmap.Width, bitmap.Height), 
                    GraphicsUnit.Pixel);

            base.Image = bitmap;
        }
    }

    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public override Image Image
    {
        get
        {
            return base.Image;
        }
        set
        {
            // ignore
        }
    }