Writing coloring algorithms

Coloring algorithms are put in coloring algorithm files with the .ucl extension. They can have the following sections, in this order:

• global
• init
• loop
• final
• default

If a coloring algorithm does not start with a label, it is assumed to start with the final section (in that case, the init and loop sections are not allowed).

The optional setting within parentheses after the entry identifier specifies whether the coloring algorithm can be used for inside coloring, outside coloring, or both. The possible values are:

If the setting is omitted, or has another value, the coloring algorithm is supposed to be useful for both inside and outside coloring. See also Inside and outside.

The global section is executed only once per image and can be used to fill look-up tables and initialize read-only variables. See Global sections.

The init section is executed only once per pixel, and is useful for initializing variables.

The loop section is executed once per iteration, right after the loop section of the fractal formula has been executed. It can read the current value of #z and perform some calculations on it.

The final section is executed afterwards to determine the actual index into the gradient (this index is further transformed by the various settings on the Inside or Outside tabs). The index is a float value and should be written to the predefined symbol #index. If the settings on the Inside or Outside tab are set to their default values (Density = 1, Transfer = Normal and Offset = 0), the entire gradient range corresponds to the range 0..1 of the index value.

To create a direct coloring algorithm, use the predefined symbol #color instead of #index.

It is also possible to set the predefined symbol #solid to true: this gives the pixel the solid color set in the Inside or Outside tab of the Layer Properties tool window.

The default section can contain the following settings:

• helpfile
• helptopic
• precision
• rating
• render
• title

It can also contain one or more parameter blocks.

Next: Writing direct coloring algorithms

See Also
Writing formulas
Coloring algorithms

Writing coloring algorithms