如何做一个伪彩色图

private void panel7_Paint(object sender, PaintEventArgs e)
        {
            //LinearGradientBrush brush = new LinearGradientBrush(e.ClipRectangle, Color.Green, Color.Blue, LinearGradientMode.Vertical);
            //e.Graphics.FillRectangle(brush, e.ClipRectangle);
        }

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

    protected override void OnPaint(PaintEventArgs e)
    {
        const int samples = 100;
        int height = 60;
        int width = this.ClientRectangle.Width / samples;

        for (int i = 0; i < samples; i++)
        {
            Color color = FromScale((double)i / samples);
            Rectangle rect = new Rectangle(width * i, 0, width, height);
            using (Brush brush = new SolidBrush(color))
            {
                e.Graphics.FillRectangle(brush, rect);
            }
        }
    }

    static Color[] colors = { Color.Blue, Color.Cyan, Color.Yellow, Color.Red };
    static Color FromScale(double value)
    {
        if (value < 0 || value > 1) throw new ArgumentException("value must be in [0~1]");

        value *= (colors.Length - 1);
        int section = Math.Min((int)Math.Floor(value), colors.Length - 2);
        double t = value - section;

        Color c1 = colors[section], c2 = colors[section + 1];
        return Color.FromArgb(
            Interpolate(t, c1.R, c2.R),
            Interpolate(t, c1.G, c2.G),
            Interpolate(t, c1.B, c2.B)
        );
    }
    static int Interpolate(double t, int i, int j)
    {
        int value = (int)(i * (1 - t) + j * t);
        return Math.Min(255, Math.Max(0, value));
    }
}