OpenCL Programming by Example

Image access qualifiers

OpenCL specification provides two types of access qualifiers for different types of image memory objects. They can be either read_only or write_only. In the following example imageA is read-only image object, and imageB is a write-only image object:

__kernel void foo (read_only image2d_t imageA,
                   write_only image2d_t imageB)

About function qualifiers and attributes, __kernel qualifier declares a function which is defined explicitly to run on an OpenCL device. A __kernel qualified function can be invoked inside another kernel function. In such a situation the kernel function just behaves as another function call. There are optional function attributes which can be specified for kernel functions.

The __kernel qualified functions ...