Changing Text Colour

Lately, I have been spending more time participating in the interesting discussions in the Revit API discussion forum than writing blog posts.

Occasionally, I grab some new code snippet worth preserving for posterity and add it to The Building Coder samples.

Even more occasionally, I actually test it   :-)  

I did so now for the trivial task of changing text colour.

Here are some notes on that and a nice node.js web scraping tutorial:

• Changing text colour via the text note type
• Web scraping using node.js

Changing Text Colour via the Text Note Type

This topic came up when Rudi @Revitalizer Honke added a comment on colours in the thread on changing colour of labels within tags family per tag instance, saying,

colour parameters are of type integer, but the raw value may be difficult to read for the user.

He explained how to read them in the earlier thread on how to change text colour:

Question: I am using the ColorDialog control from Visual Studio 2008 to select a colour, and then I retrieve the RGB components in three variables:

• ColorComponentRed
• ColorComponentGreen
• ColorComponentBlue

I want to assign this colour to some text, but the following code is not working:

  Dim colorparam As Parameter
  colorparam = elem.ObjectType.Parameter(
    BuiltInParameter.TEXT_COLOR)

  Dim app As New Autodesk.Revit.Creation.Application()
  Dim color As Autodesk.Revit.Color = app.NewColor()

  color.Red = ColorComponentRed
  color.Green = ColorComponentGreen
  color.Blue = ColorComponentBlue

  colorparam.Set(color)

Can anybody tell me what I am doing wrong and how to do it properly, please?

Answer: Hi.

  private int GetRevitTextColorFromSystemColor(
    System.Drawing.Color color )
  {
    return (int) color.R * (int) Math.Pow( 2, 0 ) 
      + (int) color.G * (int) Math.Pow( 2, 8 )
      + (int) color.B * (int) Math.Pow( 2, 16 );
  }

I know that 2^0 is just 1, so you can simplify that to:

  private int GetRevitTextColorFromSystemColor(
    System.Drawing.Color color )
  {
    return (int) color.R
      + (int) color.G * (int) Math.Pow( 2, 8 )
      + (int) color.B * (int) Math.Pow( 2, 16 );
  }

Then, for example:

  int color = GetRevitTextColorFromSystemColor( 
    yourSystemColor );

  textNoteType.get_Parameter( 
    BuiltInParameter.LINE_COLOR )
      .Set( color );

Also note that starting with Revit 2017, the Revit API provides a ColorSelectionDialog.

You can use its SelectedColor property to get a Revit colour instead of a system colour.

Richard @RPTHOMAS108 Thomas added some 'quite convenient extension methods' to that:

  <Extension()>
  Public Function AsRGB(ByVal Parameter As Parameter) As Byte()
    Dim I As Integer = Parameter.AsInteger
    Dim Red As Byte = I Mod 256
    I = I \ 256
    Dim Green As Byte = I Mod 256
    I = I \ 256
    Dim Blue As Byte = I Mod 256
    Return New Byte(2) {Red, Green, Blue}
  End Function
  <Extension()>
  Public Function AsParameterValue(ByVal Color As Color) As Integer
    Return Color.Red + (256 * Color.Green) + (65536 * Color.Blue)
  End Function
  <Extension()>
  Public Function AsParameterValue(ByVal Color As Windows.Media.Color) As Integer
    Return Color.R + (256 * Color.G) + (65536 * Color.B)
  End Function
  <Extension()>
  Public Function AsParameterValue(ByVal Color As System.Drawing.Color) As Integer
    Return Color.R + (256 * Color.G) + (65536 * Color.B)
  End Function

Many thanks to Rudi and Richard for the helpful solutions!

I added Rudi's utility function to The Building Coder samples Util.cs module like this:

  #region Colour Conversion
  /// <summary>
  /// Revit text colour parameter value stored as an integer 
  /// in text note type BuiltInParameter.LINE_COLOR.
  /// </summary>
  public static int ToColorParameterValue( 
    int red, 
    int green, 
    int blue )
  {
    return red + (green << 8) + (blue << 16);
  }

  /// <summary>
  /// Revit text colour parameter value stored as an integer 
  /// in text note type BuiltInParameter.LINE_COLOR.
  /// </summary>
  public static int GetRevitTextColorFromSystemColor( 
    System.Drawing.Color color )
  {
    return ToColorParameterValue( color.R, color.G, color.B );
  }
  #endregion // Colour Conversion

To test it, I added an additional transaction step to CmdNewTextNote:

using( Transaction t = new Transaction( doc ) )
{
  t.Start( "Change Text Colour" );

  int color = Util.ToColorParameterValue( 
    255, 0, 0 );

  Element textNoteType = doc.GetElement( 
    txNote.GetTypeId() );

  Parameter param = textNoteType.get_Parameter(
    BuiltInParameter.LINE_COLOR );

  // Note that this modifies the existing text 
  // note type for all instances using it. If
  // not desired, use Duplicate() first.

  param.Set( color );

  t.Commit();
}

As the comment says, this modifies the text note type and consequently all text note instances referring to that type.

Web Scraping Using Node.js

On a different tack, if you are interested in node.js and web scraping, here is a very pleasant and super clear 27-minute step by step introduction to basic web scraping with node.js:

It implements a minimal app live using the request-promise and cheerio libraries to gather and correlate data from two web sites.