Transformc(...)[0] does not work in OSL

Coding OSL Tests and Support
1

Hi.
I’m new to OSL.
I’m trying to make something that converts RGB to HSV and get something else out of it.
However I’m stuck right here:

shader my_osl_node(color some_color_input = 0......, output float out_float= 1.0)
{
....
    out_float = transformc("hsv", some_color_input)[0];
....
}

What I want here is to get Hue from RGB color.

  • To get specific H, S, or V (R, G, or B) channel from color, in OSL: color[int].
  • transformc returns color
  • So I’m expecting transformc(“hsv”, some_color_input)[0] to return Hue of some_color_input.

However this part of code makes syntax error. There is error message in blender console, but it does not specify what is wrong.

ERROR: C:\\Users\\_____\\AppData\\Local\\Temp\\tmp206n04zh.osl:4: error: Syntax error: syntax error
Error: OSL script compilation failed, see console for errors
2

This compiles

shader my_osl_node(color Color = 0.5, output vector out = (0))
{
    out = transformc("hsv", Color);
    
}

Or, here’s the code from T. Dinges which does work and provides H,S,V outputs.
https://raw.githubusercontent.com/sambler/osl-shaders/master/lib/TDSeparateHSV.osl