[Back to Blog](/blog) # Working with Colors in Teigha PRC

Alex Rumjantsev November 24, 2017 [\#prc](/blog/tag/prc) [\#export](/blog/tag/export) [\#Example](/blog/tag/example)

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#### Teigha PRC database organization

Each file structure has global colors and style arrays.

```
PRCFile
     OdPrcFileStructure 1
     globals().colors()
     globals().category1LineStyles()
  OdPrcFileStructure 2
     globals().colors()
     globals().category1LineStyles()
  OdPrcFileStructure 3
     globals().colors()
     globals().category1LineStyles()
…

```

A color array is an array of R,G,B values, each of which are in the 0-1 range.

A styles array is an array of OdPrcObjectId(s) and contains all the OdPrcObjectId(s) that are used in styles of the file structure.

A color should be added to the color array, and then the index of the color in the colors() array can be used in a style object. By PRC standards, the index is 0, 3, 6, 9 — an index of an R value in an array of doubles.

```
R - 0
G
B
R - 3
G
B

```

In Teigha PRC version 4.3.0, methods related to color support were redesigned. Now an “index” of a color is 0,1,2,3… — an index of color in an array.

{R,G,B} - 0

{R,G,B} - 1

Also some helper methods were added.

#### Inherited from OdPrcGraphics

Teigha PRC classes inherited from OdPrcGraphics work with color via the following:

```
OdPrcObjectId & OdPrcGraphics.styleId();

```

The style ID should be initialized with the OdPrcObjectId of an OdPrcCategory1LineStyle object.

Code example:

```
OdPrcObjectId styleId;
styleId = OdPrcCategory1LineStyle::createByColor(1, 0, 1, *curFileStructure);
pBaseWithGraphics->styleId() = styleId;

OdPrcObjectId OdPrcCategory1LineStyle::createByColor(double r, double g, double b, 
 OdPrcFileStructure &postToFileStructure, bool preventColorDuplication)

```

OdPrcCategory1LineStyle::createByColor is a helper method and does the following:

- Checks that the R,G,B values are in the 0-1 range.
- Adds the new color’s R,G,B values to the globals().colors() array.
- Creates a new style, adds it to the file structure, and adds it to category1LineStyles().
- Assigns an index of color to the new style.
- Returns the ID of the new style.

If preventColorDuplication = true, a new color is not added when a color with the same R,G,B values already exists in the colors() array.

#### OdPrcCategory1LineStyle level methods

There are a few more color-related methods in the OdPrcCategory1LineStyle class.

```
void setColor(OdPrcColorIndex colorIndex = OdPrcColorIndex::kUninit);

```

colorIndex is an index of an R,G,B color in the globals().colors() array. This method can also be used to reset a color to an unassigned value.

```
void setColor(double r, double g, double b, bool preventDuplication = false);

```

Sets R,G,B (0-1 range) color values to a style. The style must already be added to the file structure or an exception will be thrown. If preventDuplication = true, the method will search for the same color in the colors() array and will not add a new color if the color is already available.

```
OdPrcColorIndex getColor() const;

```

Returns the color index and can be used to check whether the color was initialized.

```
const OdPrcRgbColor &getTrueColor() const;

```

Returns the color as R,G,B and will throw an exception if no color is assigned or if the object is not in the database.

#### Other classes

Similar methods were added to some other classes that use colors. OdPrcDottingPattern, OdPrcMaterialGeneric, OdPrcSolidPattern, and OdPrcContentLight work with properties such as specular, emissive, and diffuse colors.

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