Invert Text Color depending on BackColor

Question

I have a ProgressBar control like the following two:

The first is painted properly. As you can see, the second only has one 0, it\'s supposed t

Answer 1

You can first draw the background and text, then draw the foreground lime rectangle using PatBlt method with PATINVERT parameter to combine foreground drawing with background drawing:

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

public class MyProgressBar : Control
{
    public MyProgressBar() 
    {
        DoubleBuffered = true;
        Minimum = 0; Maximum = 100; Value = 50;
    }
    public int Minimum { get; set; }
    public int Maximum { get; set; }
    public int Value { get; set; }
    protected override void OnPaint(PaintEventArgs e) 
    {
        base.OnPaint(e);
        Draw(e.Graphics);
    }
    private void Draw(Graphics g) 
    {
        var r = this.ClientRectangle;
        using (var b = new SolidBrush(this.BackColor))
            g.FillRectangle(b, r);
        TextRenderer.DrawText(g, this.Value.ToString(), this.Font, r, this.ForeColor);
        var hdc = g.GetHdc();
        var c = this.ForeColor;
        var hbrush = CreateSolidBrush(((c.R | (c.G << 8)) | (c.B << 16)));
        var phbrush = SelectObject(hdc, hbrush);
        PatBlt(hdc, r.Left, r.Y, (Value * r.Width / Maximum), r.Height, PATINVERT);
        SelectObject(hdc, phbrush);
        DeleteObject(hbrush);
        g.ReleaseHdc(hdc);
    }
    public const int PATINVERT = 0x005A0049;
    [DllImport("gdi32.dll")]
    public static extern bool PatBlt(IntPtr hdc, int nXLeft, int nYLeft,
        int nWidth, int nHeight, int dwRop);
    [DllImport("gdi32.dll")]
    public static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);
    [DllImport("gdi32.dll", EntryPoint = "DeleteObject")]
    public static extern bool DeleteObject(IntPtr hObject);
    [DllImport("gdi32.dll")]
    public static extern IntPtr CreateSolidBrush(int crColor);
}

Note: The controls is just for demonstrating the paint logic. For a real world application, you need to add some validation on Minimum, Maximum and Value properties.