简易调色盘控件 for .NET（EN）

By Conmajia
Originally posted in 2012

Introduction

Simple & fast implementation of a rectangular RGB palette control for .NET Fx 2.0. Old-school shit.

Name it as SRP.

Project download… Nah...

(ancient project, where on earth can I retrieve those antiques?)

The palette looks like:

▲ The look of SRP

Features

• Pick a color

  You can access the color you pick via e.Color of the ColorChanged event.

• Set palette block size

  Note that size of the whole palette will be changed.

Screenshots

Here I have several examples. SRP is formed in a 6×36 color grid.

▲ Block 5

▲ Block 10

▲ Block 15

Layers

Disassemble SRP into layers for graphic painting. (bottom to top)

1. Canvas
2. Color blocks
3. Grids
4. Border
5. Cursor

Paint It

Paint these layer sequentially.

protected override void OnPaint(PaintEventArgs e) {
  Graphics g = e.Graphics;
  drawPalette(g);
  drawGrid(g);
  drawBorder(g);
  drawCursor(g);
}

A hello to the modern Flat UI 7 yrs. ago.

void drawGrid(Graphics g) {
  for(int i = 0; i < rows; i++) {
    g.DrawLine(Pens.Black, 0, blockWidth * (i + 1), blockWidth * cols, blockWidth * (i + 1));
  }
  for(int i = 0; i < cols; i++) {
    g.DrawLine(Pens.Black, blockWidth * (i + 1), 0, blockWidth * (i + 1), blockWidth * rows);
  }
}

Calculate coordinates of a color, fill blocks, proceed on. Here’s my algorithm of generating RGB colors, you can generate your own shits.

Color getColor(int row, int col) {
  byte r = 0, g = 0, b = 0;
  int step = 0xff / (rows - 1);
  r = (byte)(row * step);
  g = (byte)(step * (col / rows));
  b = (byte)(step * (col % rows));
  return Color.FromArgb(r, g, b);
}

Instead of storing preset colors, all colors shown were automatically generated during run-time.

current = getColor(pt.Y / blockWidth, pt.X / blockWidth);

Draw mouse cursor. Refresh only dirty parts on canvas.

void updateCursor(Point pt) {
  lastCursor.X = cursor.X;
  lastCursor.Y = cursor.Y;
  cursor.X = pt.X - pt.X % blockWidth;
  cursor.Y = pt.Y - pt.Y % blockWidth;
  current = getColor(pt.Y / blockWidth, pt.X / blockWidth);
}

Redraw dirty.

protected override void OnMouseMove(MouseEventArgs e) {
  updateCursor(e.Location);
  // redraw larger spaces
  Invalidate(new Rectangle(lastCursor.X - 1, lastCursor.Y - 1, lastCursor.Width + 2, lastCursor.Height + 2));
  Invalidate(new Rectangle(cursor.X - 1, cursor.Y - 1, cursor.Width + 2, cursor.Height + 2));
  // fire event
  OnColorChanged();
}

Trigger OnColorChanged() event which happens after color is changed.

// -- custom events
public delegate void ColorChangedEventHandler(object sender, ColorChangedEventArgs e);
[Description("Fires every time when color changed.")]
public event ColorChangedEventHandler ColorChanged;
protected virtual void OnColorChanged() {
  if(ColorChanged != null) ColorChanged(this, new ColorChangedEventArgs(current));
}
// custom event args
public class ColorChangedEventArgs: EventArgs {
  Color color = Color.Black;
  public Color Color {
    get {
      return color;
    }
    set {
      color = value;
    }
  }
  public ColorChangedEventArgs(Color color): base() {
    this.color = color;
  }
}

Application

With some extra optimizations, you'll have one simple yet elegant palette.

▲ SRP in use

The End. \(\Box\)