ASP.NET Color Picker

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Introduction

On a recent project, I needed an ASP.NET color picker. I created an ASP.NET 2.0 WebControl which renders some HTML, CSS and JavaScript. No external files or libraries need to be included.

Using the Code

Extract the zip file and open the solution in Visual Studio 2005. Run the test page (default.aspx).

The color picker is a table with a lot of cells that have (web-safe) background colors:

colorpickerdiv += "<div id=\"colorpicker\">";
colorpickerdiv += "     <table cellpadding=\"0\" cellspacing=\"0\" " + 
                  "onclick=\"javascript:ColorPickerOnColorClick(event);\">";
string[] websafecolorlist = {"FFFFFF","CCCCCC","999999","666666","333333", 
        "000000","FFCC00","FF9900","FF6600","FF3300","FFFFFF",
        "FFFFFF","FFFFFF","FFFFFF","FFFFFF","FFFFFF","99CC00",
        "FFFFFF","FFFFFF","FFFFFF","FFFFFF","CC9900","FFCC33",
        "FFCC66","FF9966","FF6633","CC3300","FFFFFF","FFFFFF",
        "FFFFFF","FFFFFF","CC0033","CCFF00","CCFF33","333300",
        "666600","999900","CCCC00","FFFF00","CC9933","CC6633",
        "330000","660000","990000","CC0000","FF0000","FF3366",
        "FF0033","99FF00","CCFF66","99CC33","666633","999933",
        "CCCC33","FFFF33","996600","996600","663333","993333",
        "CC3333","FF3333","CC3366","FF6699","FF0066","66FF00",
        "99FF66","66CC33","669900","999966","CCCC66","FFFF66",
        "996633","663300","996666","CC6666","FF6666","990033",
        "CC3399","FF66CC","FF0099","33FF00","66FF33","339900",
        "66CC00","99FF33","CCCC99","FFFF99","CC9966","CC6600",
        "CC9999","FF9999","FF3399","CC0066","990066","FF33CC",
        "FF00CC","00CC00","33CC00","336600","669933","99CC66",
        "CCFF99","FFFFCC","FFCC99","FF9933","FFCCCC","FF99CC",
        "CC6699","993366","660033","CC0099","330033","33CC33",
        "66CC66","00FF00","33FF33","66FF66","99FF99","CCFFCC",
        "FFFFFF","FFFFFF","FFFFFF","CC99CC","996699","993399",
        "990099","663366","660066","006600","336633","009900",
        "339933","669966","99CC99","FFFFFF","FFFFFF","FFFFFF",
        "FFCCFF","FF99FF","FF66FF","FF33FF","FF00FF","CC66CC",
        "CC33CC","003300","00CC33","006633","339966","66CC99",
        "99FFCC","CCFFFF","3399FF","99CCFF","CCCCFF","CC99FF",
        "9966CC","663399","330066","9900CC","CC00CC","00FF33",
        "33FF66","009933","00CC66","33FF99","99FFFF","99CCCC",
        "0066CC","6699CC","9999FF","9999CC","9933FF","6600CC",
        "660099","CC33FF","CC00FF","00FF66","66FF99","33CC66",
        "009966","66FFFF","66CCCC","669999","003366","336699",
        "6666FF","6666CC","666699","330099","9933CC","CC66FF",
        "9900FF","00FF99","66FFCC","33CC99","33FFFF","33CCCC",
        "339999","336666","006699","003399","3333FF","3333CC",
        "333399","333366","6633CC","9966FF","6600FF","00FFCC",
        "33FFCC","00FFFF","00CCCC","009999","006666","003333",
        "3399CC","3366CC","0000FF","0000CC","000099","000066",
        "000033","6633FF","3300FF","00CC99","FFFFFF","FFFFFF",
        "FFFFFF","FFFFFF","0099CC","33CCFF","66CCFF","6699FF",
        "3366FF","0033CC","FFFFFF","FFFFFF","FFFFFF","FFFFFF",
        "3300CC","FFFFFF","FFFFFF","FFFFFF","FFFFFF","FFFFFF",
        "FFFFFF","00CCFF","0099FF","0066FF","0033FF","FFFFFF",
        "FFFFFF","FFFFFF","FFFFFF","FFFFFF"};

int rowcounter = 0;
bool needrowstart = true;
for (int i = 0; i < websafecolorlist.Length; i ++)
{
    if (needrowstart)
    {
        needrowstart = false;
        colorpickerdiv += "            <tr> ";
    }
    string color = "#" + websafecolorlist[i];
    colorpickerdiv += "                <td style=\"background-color:" + 
                      color + "\"></td>";
    if (rowcounter++ == 16)
    {
        colorpickerdiv += "            </tr>";
        needrowstart = true;
        rowcounter = 0;
    }
}
colorpickerdiv += "     </table>";
colorpickerdiv += "</div>";

if (!Page.ClientScript.IsClientScriptBlockRegistered("colorpickerdiv"))
    Page.ClientScript.RegisterClientScriptBlock(this.GetType(), 
                      "colorpickerdiv", colorpickerdiv);

The code above is a bit heavy and can be simplified, but the array of colors makes a nice image together. The table is surrounded by an invisible div. The table will be visible when the following code is fired:

opendialogscript += "    var ActiveColorPicker;\n";
opendialogscript += "    function OpenColorPicker(id)\n";
opendialogscript += "    {\n";
opendialogscript += "        ActiveColorPicker=id; \n";
opendialogscript += "        var colorpickerdiv=document." + 
                    "getElementById('colorpicker');\n";
opendialogscript += "        colorpickerdiv.style.visibility='visible';\n";
opendialogscript += "        colorpickerdiv.style.left=ActiveColorPicker" + 
                    ".style.left+ActiveColorPicker.style.width;\n";
opendialogscript += "        colorpickerdiv.style.top=window.event.y;\n";
opendialogscript += "        colorpickerdiv.style.left=window.event.x;\n";
opendialogscript += "    }\n";

And made invisible when a color has been clicked:

opendialogscript += "    function ColorPickerOnColorClick(e)\n";
opendialogscript += "    {\n";
opendialogscript += "        var td = (e.target) ? e.target : e.srcElement; \n";
opendialogscript += "        var color=td.style.backgroundColor; \n";
opendialogscript += "        ActiveColorPicker.style.backgroundColor=color;\n";
opendialogscript += "        ActiveColorPicker.style.color=color;\n";
opendialogscript += "        ActiveColorPicker.value=color;\n";
opendialogscript += "        var colorpickerdiv=document.getElementById('colorpicker');\n";
opendialogscript += "        colorpickerdiv.style.visibility='hidden';\n";
opendialogscript += "    }\n";

The following code is needed to render a clickable rectangle. The ID of the control is rendered with this.UniqueID. To store the color value, I use the value attribute from the textbox.

protected override void Render(HtmlTextWriter output)
{
    string html = "";
    string onclicker="onclick=\"javascript:OpenColorPicker(" + 
                     this.UniqueID + ");\"";
    html += "<input style=\"background-color:" + 
            SelectedHexValue + ";color:" + SelectedHexValue + 
            ";\" class=\"colorpickerbutton\" " + 
            onclicker + " readonly=\"true\" class=\"lookupmo" + 
            "dalvalue\" type=\"text\" name=\"" + 
            this.UniqueID + "\" value=\"" + 
            SelectedHexValue + "\">";
    output.Write(html);
}

Retrieving the value after a postback is done in LoadPostData:

public bool LoadPostData(String postDataKey, NameValueCollection values)
{
    SelectedHexValue = values[this.UniqueID];
    return false;
}

The color code can be get or set with the SelectedHexValue property. If you need a Color object or RGB int, just add properties that convert the HEX-code.

Label1.Text = ColorPicker1.SelectedHexValue;

Points of Interest

About web controls: LoadPostData is a tricky event. In order for it to fire, you must name one of the HTML controls exactly like the UniqueID of the control!

If you have any comments regarding the code, please feel free to email me at: colorpicker@toverstudio.nl.

History

• 2006-07-11: Release 1.0.

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)