read_imagef (3D)

Do an element lookup in the 3D image object, returning floating-point values.

float4 read_imagef ( image3d_t image,
  sampler_t sampler,
  int4 coord)
float4 read_imagef ( 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_imagef returns floating-point values in the range [0.0... 1.0] for image objects created with image_channel_data_type set to one of the predefined packed formats or CL_UNORM_INT8 or CL_UNORM_INT16.

read_imagef returns floating-point values in the range [-1.0... 1.0] for image objects created with image_channel_data_type set to CL_SNORM_INT8, or CL_SNORM_INT16.

read_imagef returns floating-point values for image objects created with image_channel_data_type set to CL_HALF_FLOAT or CL_FLOAT.

The read_imagef calls that take integer coordinates must use a sampler with filter mode set to CLK_FILTER_NEAREST, 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.

Values returned by read_imagef for image objects with image_channel_data_type values not specified in the description above 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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