Preserving the element color in the Navisworks database

Background of the problem

There was a customer task, for example, such:

• Drop in 1C elements of the building model.
• In 1C to use these parts of the model in contracts - well, let's say, indicate that such and such elements have already been built, such and such are only planned, and so on.
• In the Navisworks on the drawing somehow see this - for example, by displaying the elements of the model in different colors. For this, a plugin was made to Navisworks that can copy data from Quantification tables (Takeoff tables) to 1C, and also take them back from 1C and stuff them into Takeoff tables.
  And in 1C, it was intended to change the colors of the model elements (premises) used in the contract.

But it turned out that after changing these tabular data in 1C - Navisworks does not understand that they have changed, and it would be necessary to update them. So, I, a programmer, need to tell him that.

So, the task for the programmer

After the exchange with 1C, the data in the TK_Item table has changed - in particular, the Color field. It is necessary to bring the colors on the displayed drawing in accordance with those indicated in the table.

We are looking for how to do it. Digging a description. Find the function -

public void OverridePermanentColor(IEnumerable<ModelItem> items, Color color) 

Well, how to find the elements of the model that match the selected item TK_Item is another story, another time I will tell if it will be interesting. But who needs - and he will understand. But with the color everything turned out to be more interesting.
First of all, the Color specified in the function parameters is not System.Drawing.Color, but even Autodesk.Navisworks.Api.Color, with its own blackjack and ... well, you understand. Well, let him, but he has this constructor:

 public static unsafe Color FromByteRGB(byte red, byte green, byte blue) 

So, without any problems we will make such a Color, which Avtodeskovsky API is needed.
(Actually, the first thing I do is try - find the items that match the selected Item, choose a color - and set it to them.)

But. In the table, we have one value of type Int64 in the Color field. And how to compare it with an object of type Color is not clear.

And neither in the documentation, nor on the forum, nor in the examples I could not find how it is written in the database.

OK, we will dig experimentally.

Take Navisworks, open Quantification, change the color of some element. Let's say honest to the pure Red.

After that, we take our plugin, we extort data from the TK_Item table, and see what is in the table?

(Fortunately, in the plugin for debugging purposes, this option was provided - download the data and show it on the form.)

There, it turns out, is -65536.

We repeat the procedure several times and reduce the results to a text file.

At first I was very surprised by the numbers in the table, and especially by the presence of positive and negative values.

Experimenting with the values ​​of the components R, G, B, I realized that these three components are displayed in the last three bytes of the number.

But then it is strange - why are the high bytes turned out to be filled not with zeros, but with ones?
However, if we assume that they are always filled with units, then the presence of negative numbers is explained. Just fill and high byte, which determines the sign of the number.
But there are not always negative numbers!

And just remembering how the functions >> and << work, I realized that they can stupidly fill in the high bits, including the sign bit, with digits. And since the high-order bits are not needed, it doesn’t matter what stands there.

Then the question is - but what the hell did they need so much importance for the color? Already 64 bits? I looked at the structure of the tables in which this data is stored - Int64 is simply used for all integers. Indeed, why trivial?

Total

The color value recorded in the table, we obtain as follows:

 Int64 dbColor = Rb<<16 + Gb<<8 + Bb; 

Inverse transformation - table color to the color used for model elements - do this:

 byte R = (byte)(dbColorValue >> 16 % 256); byte G = (byte)(dbColorValue >> 8 % 256); byte B = (byte) (dbColorValue % 256); var color = Autodesk.Navisworks.Api.Color.FromByteRGB(R, G, B);