WPF : A Simple Color Picker With Preview

• Download code : 1,410 KB

Contents

• Introduction
• The Code
• So What Do You Think ?

Introduction

Yesterday I posted an article about creating a WPF Graph and when I post a new article I always have a look at the new articles, including those awaiting public status. Yesterday someone publised a WPF color picker, that looked really cool. The only problem was the code was not attached to that article and the article text gave you no clue as to how the damn thing worked. I joked to a fellow code project author that I just may have to try and write a color picker for WPF, as this article sparked my interest a bit.

As luck would have it, I woke up today (Monday) and tried to get into work (I work in London and live 50 mile aways), but was faced with the worst snow storm in the UK for some time. No trains/buses/taxis we on, so guess what I did. That's right, I wrote a color picker.

This article is it.

It is very simple actually. I should point out before I start that I did borrow an idea or 2 from other exellent sources from the www. So I would like to start by having a special thanks section.

Special Thanks Goes Out To

• Lee Brimelow : For his idea of having an image swatch image, and copying the pixel under the mouse. Read more about this at Lees blog

  http://thewpfblog.com/?p=62

• ShawnVN's Blog : For his idea of having an a preview area and a Alpha slider. Read more about his alternative honeycomb color picker over at his blog

  http://weblogs.asp.net/savanness/archive/2006/12/05/colorcomb-yet-another-color-picker-dialog-for-wpf.aspx

The Code

So how does it all work. Well it is actually so simple you probably would think "Ha, is that it". Well yep, this next section explains all that is inviolved which aint that much. Simplicity is good.

There is a WPF Window called ColorDialog which holds the actual ColorPicker control. Here is the XAML:

<Window x:Class="WPFColorPickerLib.ColorDialog"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:WPFColorPickerLib"
    Icon="Images/ColorSwatchSquare.png"
    Title="Pick Color" Height="370" 
    KeyDown="Window_KeyDown"
    Width="520" WindowStartupLocation="CenterOwner">
    
    <local:ColorPicker x:Name="colorPicker"/>
        
</Window>

This ColorDialog window is the one you can use from your own code. The ColorDialog window exposes a single property which is really just the value of the currently selected color within the contained ColorPicker control.

Here is the code behind for the ColorDialog window:

public partial class ColorDialog : Window
{
    #region Ctor
    public ColorDialog()
    {
        InitializeComponent();
    }
    #endregion

    #region Public Properties
    public Color SelectedColor
    {
        get { return colorPicker.SelectedColor; }
    }
    #endregion

    #region Private Methods
    /// <summary>
    /// Closes the dialog on Enter key pressed
    /// </summary>
    private void Window_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Enter)
        {
            this.Close();
        }
    }

    /// <summary>
    /// User is happy with choice
    /// </summary>
    private void btnOk_Click(object sender, RoutedEventArgs e)
    {
        DialogResult = true;
    }

    /// <summary>
    /// User is not happy with choice
    /// </summary>
    private void btnCancel_Click(object sender, RoutedEventArgs e)
    {
        DialogResult = false;
    }
    #endregion
}

And here is how you could use it from your own WPF code to set a Color:

private void btnPickColor_Click(object sender, RoutedEventArgs e)
{
    ColorDialog colorDialog = new ColorDialog();
    colorDialog.Owner = this;
    if ((bool)colorDialog.ShowDialog())
    {
        RectColorPicked.Fill = new SolidColorBrush(colorDialog.SelectedColor);
    }
}

The actual ColorPicker control works as follows:

There are a number of static swatch images

That the user may pick from using the image buttons provided at the top of the ColorPicker control. The user is then able to use the mouse to move around the image, and also adjust the Alpha value using the slider. The SelectedColor is worked out based on where the mouse is in relationship to the current static swatch image. Basically a single pixel under the mouse is retrieved from the current static swatch image, and this is made into a 1*1 byte array, and then the values within this 1*1 byte array are used to create a Color, taking into account the current Alpha slider value.

The following diagram may help to explain it a little better.

One of the nice things about this control is the Preview, which is simply using a WPF InkPresenter control and showing some strokes on it. And the nice checker background is easily ahcieved in WPF using a DrawingBrush.

In essence that is how it works, so probably time for some code.

Here is the entire XAML for the ColorPicker control.

<UserControl x:Class="WPFColorPickerLib.ColorPicker"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="340" Width="510">


    <UserControl.Resources>
        <DrawingBrush x:Key="CheckerboardBrush" 
        Stretch="None" TileMode="Tile" AlignmentX="Left" AlignmentY="Top" 
        Viewport="0,0,10,10" ViewportUnits="Absolute">
            <DrawingBrush.Drawing>
                <DrawingGroup>
                    <GeometryDrawing Brush="sc# 1,1,1">
                        <GeometryDrawing.Geometry>
                            <RectangleGeometry Rect="0,0,10,10" />
                        </GeometryDrawing.Geometry>
                    </GeometryDrawing>
                    <GeometryDrawing Brush="sc# 0.5,0.5,0.5">
                        <GeometryDrawing.Geometry>
                            <RectangleGeometry Rect="0,0,5,5" />
                        </GeometryDrawing.Geometry>
                    </GeometryDrawing>
                    <GeometryDrawing Brush="sc# 0.5,0.5,0.5">
                        <GeometryDrawing.Geometry>
                            <RectangleGeometry Rect="5,5,5,5" />
                        </GeometryDrawing.Geometry>
                    </GeometryDrawing>
                </DrawingGroup>
            </DrawingBrush.Drawing>
        </DrawingBrush>
    </UserControl.Resources>

    
    <Grid Background="White">

        <Grid.RowDefinitions>
            <RowDefinition Height="35"/>
            <RowDefinition Height="230"/>
            <RowDefinition Height="70"/>
        </Grid.RowDefinitions>

        <StackPanel Grid.Row="0" Height="35" 
                    HorizontalAlignment="Stretch" Orientation="Horizontal" 
                    Background="Black">
            <Label Content="Pick swatch type" Foreground="White" FontWeight="Bold" 
                   VerticalAlignment="Center"/>
            <Image x:Name="ImgSqaure1" Height="20" Width="20" 
                   Source="Images/ColorSwatchSquare.png" Margin="45,0,0,0" 
                   ToolTip="Square swatch1" 
                   MouseLeftButtonDown="Swatch_MouseLeftButtonDown"/>
            <Image x:Name="ImgSqaure2" Height="20" Width="20" 
                   Source="Images/ColorSwatchSquare2.png" Margin="5,0,0,0" 
                   ToolTip="Square swatch2" 
                   MouseLeftButtonDown="Swatch_MouseLeftButtonDown"/>
            <Image x:Name="ImgCircle1" Height="20" Width="20" 
                   Source="Images/ColorSwatchCircle.png" Margin="5,0,0,0" 
                   ToolTip="Circle swatch1" 
                   MouseLeftButtonDown="Swatch_MouseLeftButtonDown"/>
        </StackPanel>

        <Grid Grid.Row="1" Height="230" VerticalAlignment="Top">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="170"/>
                <ColumnDefinition Width="170"/>
                <ColumnDefinition Width="170"/>
            </Grid.ColumnDefinitions>

            <!-- Colorbox, Column1-->
            <Grid Grid.Column="0" Grid.Row="0" Margin="10,30,0,0" >

                <Border BorderBrush="Black" BorderThickness="2" 
                    HorizontalAlignment="Center" VerticalAlignment="Top"
                        Background="White"
                        Width="154" Height="154">
                </Border>
              
                
                
                <Image x:Name="ColorImage" Width="150" Height="150" 
                       HorizontalAlignment="Center"
                       VerticalAlignment="Top" Margin="2"
                       Source="Images/ColorSwatchSquare.png"/>

                <Canvas x:Name="CanvImage" Width="150" Height="150" 
                       HorizontalAlignment="Center"
                       Background="Transparent"
                       VerticalAlignment="Top" Margin="2"
                       MouseDown="CanvImage_MouseDown"
                       MouseUp="CanvImage_MouseUp"
                       MouseMove="CanvImage_MouseMove">
                    <Ellipse x:Name="ellipsePixel" Width="10" 
                       Height="10" Stroke="Black" Fill="White" 
                       Canvas.Left="0" Canvas.Top="0"/> 
                    
                </Canvas>


            </Grid>

            <!-- Preview, Column1-->
            <StackPanel Grid.Column="1" Orientation="Vertical" >
                <Label Content="Preview" Margin="5,0,0,0" HorizontalAlignment="Left" 
                       Foreground="Black" FontWeight="Bold" VerticalAlignment="Center"/>

                <Border Margin="4,5,10,0" Width="154" Height="154" 
                        HorizontalAlignment="Left" BorderBrush="Black" BorderThickness="2"
                        Background="{StaticResource CheckerboardBrush}">
                    <InkPresenter Name="previewPresenter" Margin="0" Width="150" Height="150"
                        Strokes="AOcBAxdIEESAgYAERYQBGwIAJAFGhAEbAgAkAQUBOBkgMgkA9P8CAekiOkU
						zCQD4nwIBWiA6RTgIAP4DAAAAgH8RAACAPx8JEQAAAAAAAPA/CpYBNIfm3uajgcQgUU
						iUkjUelEal0KkUBh0HichlM1mtJotZp9JodDl8jk8ZgcBiUOjUYl08m0+l0+lFCjksjE
						SAh+kg6auNwaEwSBQiEQyLRKTRiVSiUSSORyLQ6JQSBIPFYnKZTL5fOZfMZXL4/H47DY
						LBYHFoJLIpEo9GgIP3OB5PlxLCJiZmU1MISSi4SJiS74+D4+4o" />
                </Border>

            </StackPanel>

            <!-- TextBoxes, Column2-->
            <StackPanel Grid.Column="2" Orientation="Vertical" >

                <StackPanel Orientation="Horizontal" Margin="0,30,0,0">
                    <Label Content="A" Margin="5,0,0,0" HorizontalAlignment="Left" 
                            Foreground="Black" FontWeight="Bold" VerticalAlignment="Center"/>
                    <Border CornerRadius="5" BorderBrush="Black" Background="LightGray" 
                            BorderThickness="2" Width="50" Height="30">
                        <TextBox x:Name="txtAlpha" BorderThickness="0" Background="LightGray" 
                            BorderBrush="Transparent" Margin="5,1,5,1" IsReadOnly="True"/>
                    </Border>
                    <Border CornerRadius="5" BorderBrush="Black" Background="LightGray" 
                            BorderThickness="2" Margin="10,0,0,0" Width="50" Height="30">
                        <TextBox x:Name="txtAlphaHex" BorderThickness="0" 
                            Background="LightGray" BorderBrush="Transparent"
                            Margin="5,1,5,1" IsReadOnly="True"/>
                    </Border>
                </StackPanel>

                <StackPanel Orientation="Horizontal" Margin="0,5,0,0">
                    <Label Content="R" Margin="5,0,0,0" HorizontalAlignment="Left" 
                            Foreground="Black" FontWeight="Bold" VerticalAlignment="Center"/>
                    <Border CornerRadius="5" BorderBrush="Black" Background="LightGray" 
                            BorderThickness="2" Width="50" Height="30">
                        <TextBox x:Name="txtRed" BorderThickness="0" Background="LightGray" 
                            BorderBrush="Transparent" Margin="5,1,5,1" IsReadOnly="True"/>
                    </Border>
                    <Border CornerRadius="5" BorderBrush="Black" Background="LightGray" 
                            BorderThickness="2" Margin="10,0,0,0" Width="50" Height="30">
                        <TextBox x:Name="txtRedHex" BorderThickness="0" Background="LightGray" 
                            BorderBrush="Transparent" Margin="5,1,5,1" IsReadOnly="True"/>
                    </Border>
                </StackPanel>

                <StackPanel Orientation="Horizontal" Margin="0,5,0,0">
                    <Label Content="G" Margin="5,0,0,0" HorizontalAlignment="Left" 
                            Foreground="Black" FontWeight="Bold" 
                            VerticalAlignment="Center"/>
                    <Border CornerRadius="5" BorderBrush="Black" Background="LightGray" 
                            BorderThickness="2" Width="50" Height="30">
                        <TextBox x:Name="txtGreen" BorderThickness="0" 
                            Background="LightGray" BorderBrush="Transparent" 
                            Margin="5,1,5,1" IsReadOnly="True"/>
                    </Border>
                    <Border CornerRadius="5" BorderBrush="Black" Background="LightGray"
                            BorderThickness="2" Margin="10,0,0,0" Width="50" Height="30">
                        <TextBox x:Name="txtGreenHex" BorderThickness="0"
                            Background="LightGray" BorderBrush="Transparent" 
                            Margin="5,1,5,1" IsReadOnly="True"/>
                    </Border>
                </StackPanel>

                <StackPanel Orientation="Horizontal" Margin="0,5,0,0">
                    <Label Content="B" Margin="5,0,0,0" HorizontalAlignment="Left" 
                           Foreground="Black" FontWeight="Bold" 
                           VerticalAlignment="Center"/>
                    <Border CornerRadius="5" BorderBrush="Black" Background="LightGray" 
                           BorderThickness="2" Width="50" Height="30">
                        <TextBox x:Name="txtBlue" BorderThickness="0" Background="LightGray" 
                           BorderBrush="Transparent" Margin="5,1,5,1" IsReadOnly="True"/>
                    </Border>
                    <Border CornerRadius="5" BorderBrush="Black" Background="LightGray" 
                            BorderThickness="2" Margin="10,0,0,0" Width="50" Height="30">
                        <TextBox x:Name="txtBlueHex" BorderThickness="0" 
                            Background="LightGray" BorderBrush="Transparent" 
                            Margin="5,1,5,1" IsReadOnly="True"/>
                    </Border>
                </StackPanel>

                <StackPanel Orientation="Horizontal" Margin="0,5,0,0">
                    <Border CornerRadius="5" Margin="22,0,0,0" Background="LightGray" 
                            BorderBrush="Black" BorderThickness="2" Width="112" Height="30">
                        <TextBox x:Name="txtAll" BorderThickness="0" Background="LightGray" 
                            BorderBrush="Transparent" Margin="5,1,5,1" IsReadOnly="True"/>
                    </Border>
                </StackPanel>
                
            </StackPanel>
            
        </Grid>

        <!--AlphaSlider-->
        <Border x:Name="AlphaBorder" Grid.Row="2" Grid.ColumnSpan="2" 
                BorderBrush="Black" Height="60"
                BorderThickness="2" CornerRadius="5" Margin="10,5,10,5">
            <Slider x:Name="AlphaSlider" Orientation="Horizontal" 
                Minimum="0" Maximum="255" 
                SmallChange="1" LargeChange="25"
                VerticalAlignment="Center" Margin="5" 
                Value="255"
                ValueChanged="AlphaSlider_ValueChanged"/>

        </Border>

    </Grid>
</UserControl>

And here is all the C# code behind for the ColorPicker control.

public partial class ColorPicker : UserControl
{
    #region Data
    private DrawingAttributes drawingAttributes = new DrawingAttributes();
    private Color selectedColor = Colors.Transparent;
    private Boolean IsMouseDown = false;
    #endregion

    #region Ctor
    public ColorPicker()
    {
        InitializeComponent();
        this.Loaded += new RoutedEventHandler(ColorPicker_Loaded);
    }
    #endregion

    #region Public Properties
    /// <summary>
    /// gets or privately sets the selected
    /// Color. When the Color is set 
    /// the CreateAlphaLinearBrush()/UpdateTextBoxes()
    /// and UpdateInk() methods are called
    /// </summary>
    public Color SelectedColor
    {
        get { return selectedColor; }
        private set
        {
            if (selectedColor != value)
            {
                selectedColor = value;
                CreateAlphaLinearBrush();
                UpdateTextBoxes();
                UpdateInk();
            }
        }
    }
    #endregion

    #region Private Methods
    /// <summary>
    /// Start with a default Color of black
    /// </summary>
    private void ColorPicker_Loaded(object sender, RoutedEventArgs e)
    {
        SelectedColor = Colors.Black;
    }

    /// <summary>
    /// Creates a new LinearGradientBrush background for the
    /// Alpha area slider. This is based on the current color
    /// </summary>
    private void CreateAlphaLinearBrush()
    {
        Color startColor = Color.FromArgb(
                (byte)0,
                SelectedColor.R, 
                SelectedColor.G, 
                SelectedColor.B);

        Color endColor = Color.FromArgb(
                (byte)255,
                SelectedColor.R, 
                SelectedColor.G, 
                SelectedColor.B);

        LinearGradientBrush alphaBrush = 
            new LinearGradientBrush(startColor, endColor, 
                new Point(0, 0), new Point(1, 0));

        AlphaBorder.Background = alphaBrush;
    }


    /// <summary>
    /// apply the new Swatch image based on user requested swatch
    /// </summary>
    private void Swatch_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        Image img = (sender as Image);
        ColorImage.Source = img.Source;
    }


    /// <summary>
    /// Simply grab a 1*1 pixel from the current color image, and
    /// use that and copy the new 1*1 image pixels to a byte array and
    /// then construct a Color from that.
    /// </summary>
    private void CanvImage_MouseMove(object sender, MouseEventArgs e)
    {
        if (!IsMouseDown)
            return;

        try
        {
            CroppedBitmap cb = new CroppedBitmap(ColorImage.Source as BitmapSource,
                new Int32Rect((int)Mouse.GetPosition(CanvImage).X,
                    (int)Mouse.GetPosition(CanvImage).Y, 1, 1));

            byte[] pixels = new byte[4];

            try
            {
                cb.CopyPixels(pixels, 4, 0);
            }
            catch (Exception ex)
            {
                //Ooops
            }

            //Ok now, so update the mouse cursor position and the SelectedColor
            ellipsePixel.SetValue(Canvas.LeftProperty,(double)(Mouse.GetPosition(CanvImage).X-5));
            ellipsePixel.SetValue(Canvas.TopProperty, (double)(Mouse.GetPosition(CanvImage).Y-5));
            CanvImage.InvalidateVisual();
            SelectedColor = Color.FromArgb((byte)AlphaSlider.Value, pixels[2], pixels[1], pixels[0]);
        }
        catch (Exception exc)
        {
            //not much we can do
        }
    }

    /// <summary>
    /// Update text box values based on SelectedColor
    /// </summary>
    private void UpdateTextBoxes()
    {
        txtAlpha.Text = SelectedColor.A.ToString();
        txtAlphaHex.Text = SelectedColor.A.ToString("X");
        txtRed.Text = SelectedColor.R.ToString();
        txtRedHex.Text = SelectedColor.R.ToString("X");
        txtGreen.Text = SelectedColor.G.ToString();
        txtGreenHex.Text = SelectedColor.G.ToString("X");
        txtBlue.Text = SelectedColor.B.ToString();
        txtBlueHex.Text = SelectedColor.B.ToString("X");
        txtAll.Text = String.Format("#{0}{1}{2}{3}",
                txtAlphaHex.Text, txtRedHex.Text, 
                txtGreenHex.Text, txtBlueHex.Text);
    }

    /// <summary>
    /// Updates Ink stroked based on SelectedColor
    /// </summary>
    private void UpdateInk()
    {
        drawingAttributes.Color = SelectedColor;
        drawingAttributes.StylusTip = StylusTip.Ellipse;
        drawingAttributes.Width = 5;

        // Update DA on previewPresenter
        foreach (Stroke s in previewPresenter.Strokes)
        {
            s.DrawingAttributes = drawingAttributes;
        }
    }

    /// <summary>
    /// Update SelectedColor Aplha based on Slider value
    /// </summary>
    private void AlphaSlider_ValueChanged(object sender, 
        RoutedPropertyChangedEventArgs<double> e)
    {
        SelectedColor = 
            Color.FromArgb(
                (byte)AlphaSlider.Value,
                SelectedColor.R, 
                SelectedColor.G, 
                SelectedColor.B);
    }

    /// <summary>
    /// Change IsMouseDown state
    /// </summary>
    private void CanvImage_MouseDown(object sender, MouseButtonEventArgs e)
    {
        IsMouseDown = true;
    }

    /// <summary>
    /// Change IsMouseDown state
    /// </summary>
    private void CanvImage_MouseUp(object sender, MouseButtonEventArgs e)
    {
        IsMouseDown = false;
    }
    #endregion

}

So What Do You Think ?

I would just like to ask, if you liked the article please vote for it, and leave some comments, as it lets me know if the article was at the right level or not, and whether it contained what people need to know.