2011

Image Processing Algorithm Categories
There are three types of image processing operators: the point operator, the
gather operator, and the scatter operator. They are based on a workflow in
which there are one or more input images and a single output image:
■ Point operator Image processing operation that only reads pixels from
the input images at the current position, and only writes one pixel to the
output image, at the same position.
■ Gather operator Image processing operation that reads pixels from the
input images from any position, and only writes one pixel to the output
image, at the current position.
■ Scatter operator Image processing operation that reads pixels from the
input images from any position and writes one or more pixels to the output
image at any position.
NOTE The PXL tool can perform point and gather operations, but not scatter
operations.
Fundamental Types
PXL supports a specific set of fundamental types. It is case sensitive. Like C,
all the variables must be declared before they can be used in an expression
statement, unless the variable is a built-in variable, or a function argument.
Unlike the C++ language, it is not possible to define new types with objects
or structures. Here is the list of supported fundamental types:
■ image
■ float
■ color/vec4
The color and vec4 types are aliases of one another, and are provided for
convenience and readability. Otherwise, they are syntactically identical for
PXL, and can be used interchangeably. Any reference in the documentation
to type color can be understood as vec4, and vice versa.
NOTE PXL does not support vectors, arrays, or matrices.
The color / vec4 type is a quadruplet of floating point values for R, G, B, and
A (or equivalently, X, Y, Z and W). These values are unclamped (even for A),
which fully supports high dynamic range scene-referred color manipulation.
PXL, the Pixel eXpression Language | 457