2011

Interface with Composite Executable
The Composite executable interfaces with the PXL script in the following way:
■ The function declaration is optional. If present, it must be called “main()”.
■ Function arguments can be any of the PXL basic types. Arguments to
“main()” of type “image” with the “input” qualifier are the PXL tool image
inputs, and must match the name of the input image socket. This implies
that accessing the primary image input must be done with an input image
argument named “In”. Arguments to “main()” of non-image type with the
“input” qualifier are PXL tool parameter inputs, and are matched by name
and type with the input parameters of the PXL tool. For example, a float
parameter named “Gain” would be passed in the “main()” function as
“input float Gain”. Arguments to “main()” of type “color” with the
“output” qualifier are the pixel outputs. The first version of the PXL tool
supports a single pixel output, which must be called “Out”.
■ The return type is limited to void and the return statement is not supported.
If no function header is present for main(), Composite will create one
automatically. It will include all defined image inputs, and all defined
parameter inputs.
No warning is given if main() function arguments are not referenced by the
function. However, a reference to a non-existent parameter or input image is
an error.
462 | Chapter 18 Pixel Expressions