read_imagei (3D)

Do an element lookup in the 3D image object, returning unnormalized signed integer and unsigned integer values

int 4 read_imagei ( image3d_t image,
  sampler_t sampler,
  int4 coord)
int 4 read_imagei ( image3d_t image,
  sampler_t sampler,
  float4 coord)
unsigned int4 read_imageui ( image3d_t image,
  sampler_t sampler,
  int4 coord)
unsigned int4 read_imageui ( image3d_t image,
  sampler_t sampler,
  float4 coord)

Description

Use the coordinate (coord.x, coord.y, coord.z)) to do an element lookup in the 3D image object specified by image. coord.w is ignored.

read_imagei and read_imageu{i|ui} 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 and read_image{i|ui} calls that take integer coordinates must use a sampler with normalized coordinates set to CLK_NORMALIZED_COORDS_FALSE and addressing mode set to CLK_ADDRESS_CLAMP_TO_EDGE, CLK_ADDRESS_CLAMP or CLK_ADDRESS_NONE; otherwise the values returned are undefined.

Notes

The following table describes the mapping of the number of channels of an image element to the appropriate components in the float4, int4 or unsigned int4 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 unsigned int4 components of channel data
CL_R (r, 0.0, 0.0, 1.0)
CL_A (0.0, 0.0, 0.0, a)
CL_RG (r, g, 0.0, 1.0)
CL_RA (r, 0.0, 0.0, a)
CL_RGB (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)

Specification

OpenCL Specification

Also see

Image Functions

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