Provided by: opencl-1.2-man-doc_1.0~svn33624-5_all 
NAME
read_image{i|ui}_(1D) - Do an element lookup in the 1D image object, returning unnormalized signed
integer and unsigned integer values.
int4 read_imagei(image1d_t image, sampler_t sampler, int coord);
int4 read_imagei(image1d_t image, sampler_t sampler, float coord);
uint4 read_imageui(image1d_t image, sampler_t sampler, int coord);
uint4 read_imageui(image1d_t image, sampler_t sampler, float coord);
int4 read_imagei(image1d_t image, int coord);
uint4 read_imageui(image1d_t image, int coord);
int4 read_imagei(image1d_buffer_t image, int coord);
uint4 read_imageui(image1d_buffer_t image, int coord);
int4 read_imagei(image1d_array_t image, int2 coord);
uint4 read_imageui(image1d_array_t image, int2 coord);
int4 read_imagei(image1d_array_t image, sampler_t sampler, int2 coord);
int4 read_imagei(image1d_array_t image, sampler_t sampler, float2 coord);
uint4 read_imageui(image1d_array_t image, sampler_t sampler, int2 coord);
uint4 read_imageui(image1d_array_t image, sampler_t sampler, float2 coord);
DESCRIPTION
For the forms that take an image1d_t, use the coordinate (coord.x, coord.y) to do an element lookup in
the 2D image object specified by image.
For the forms that take an image1d_array_t, use coord.x to do an element lookup in the 1D image
identified by coord.y in the 1D image array specified by image.
The samplerless read image functions behave exactly as the corresponding read image functions that take
integer coordinates and a sampler with filter mode set to CLK_FILTER_NEAREST, normalized coordinates set
to CLK_NORMALIZED_COORDS_FALSE and addressing mode to CLK_ADDRESS_NONE.
read_imagei and read_imageui return unnormalized signed integer and unsigned integer values respectively.
Each channel will be stored in a 32-bit integer.
read_imagei can only be used with image objects created with image_channel_data_type set to one of the
following values: CL_SIGNED_INT8, CL_SIGNED_INT16, or CL_SIGNED_INT32. If the image_channel_data_type is
not one of the above values, the values returned by read_imagei are undefined.
read_imageui can only be used with image objects created with image_channel_data_type set to one of the
following values: CL_UNSIGNED_INT8, CL_UNSIGNED_INT16, and CL_UNSIGNED_INT32. If the
image_channel_data_type is not one of the above values, the values returned by read_imageui are
undefined.
The read_imagei and read_imageui calls support a nearest filter only. The filter_mode specified in
sampler must be set to CLK_FILTER_NEAREST; otherwise the values returned are undefined.
Furthermore, the read_imagei returned are undefined. and read_imageui calls that take integer coordinates
must use a returned are undefined. sampler with normalized coordinates set to CLK_NORMALIZED_COORDS_FALSE
and addressing returned are undefined. mode set to CLK_ADDRESS_CLAMP_TO_EDGE, CLK_ADDRESS_CLAMP or
CLK_ADDRESS_NONE; otherwise returned are undefined. the values returned are undefined. returned are
undefined.
NOTES
The built-in functions defined in this section can only be used with image memory objects. An image
memory object can be accessed by specific function calls that read from and/or write to specific
locations in the image.
Image memory objects that are being read by a kernel should be declared with the accessQualifiers(3clc)
qualifier. write_image calls to image memory objects declared with the accessQualifiers(3clc) qualifier
will generate a compilation error. Image memory objects that are being written to by a kernel should be
declared with the accessQualifiers(3clc) qualifier. read_image calls to image memory objects declared
with the accessQualifiers(3clc) qualifier will generate a compilation error. read_image and write_image
calls to the same image memory object in a kernel are not supported.
The read_image calls returns a four component floating-point, integer or unsigned integer color value.
The color values returned by read_image are identified as x, y, z, w where x refers to the red component,
y refers to the green component, z refers to the blue component and w refers to the alpha component.
The following table describes the mapping of the number of channels of an image element to the
appropriate components in the float4, int4 or uint4 vector data type for the color values returned by
read_image{f|i|ui} or supplied to write_image{f|i|ui}. The unmapped components will be set to 0.0 for
red, green and blue channels and will be set to 1.0 for the alpha channel.
┌───────────────────────────┬─────────────────────────────────────┐
│ Channel Order │ float4, int4 or uint4 components of │
│ │ channel data │
├───────────────────────────┼─────────────────────────────────────┤
│ CL_R, CL_Rx │ (r, 0.0, 0.0, 1.0) │
├───────────────────────────┼─────────────────────────────────────┤
│ CL_A │ (0.0, 0.0, 0.0, a) │
├───────────────────────────┼─────────────────────────────────────┤
│ CL_RG, CL_RGx │ (r, g, 0.0, 1.0) │
├───────────────────────────┼─────────────────────────────────────┤
│ CL_RA │ (r, 0.0, 0.0, a) │
├───────────────────────────┼─────────────────────────────────────┤
│ CL_RGB, CL_RGBx │ (r, g, b, 1.0) │
├───────────────────────────┼─────────────────────────────────────┤
│ CL_RGBA, CL_BGRA, CL_ARGB │ (r, g, b, a) │
├───────────────────────────┼─────────────────────────────────────┤
│ CL_INTENSITY │ (I, I, I, I) │
├───────────────────────────┼─────────────────────────────────────┤
│ CL_LUMINANCE │ (L, L, L, 1.0) │
└───────────────────────────┴─────────────────────────────────────┘
A kernel that uses a sampler with the CL_ADDRESS_CLAMP addressing mode with multiple images may result in
additional samplers being used internally by an implementation. If the same sampler is used with multiple
images called via read_image{f|i|ui}, then it is possible that an implementation may need to allocate an
additional sampler to handle the different border color values that may be needed depending on the image
formats being used. These implementation allocated samplers will count against the maximum sampler values
supported by the device and given by CL_DEVICE_MAX_SAMPLERS. Enqueuing a kernel that requires more
samplers than the implementation can support will result in a CL_OUT_OF_RESOURCES error being returned.
SPECIFICATION
OpenCL Specification[1]
SEE ALSO
imageFunctions(3clc)
AUTHORS
The Khronos Group
COPYRIGHT
Copyright © 2007-2011 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or
associated documentation files (the "Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to
the condition that this copyright notice and permission notice shall be included in all copies or
substantial portions of the Materials.
NOTES
1. OpenCL Specification
page 292, section 6.12.14 - Image Read and Write Functions
The Khronos Group 01/14/2021 READ_IMAGEI (1D)(3clc)