write_image

Description

For write_imagef, write_imagei, write_imageh, and write_imageui forms that take image2d_t

Write color value to location specified by coord.xy in the 2D image object specified by image. Appropriate data format conversion to the specified image format is done before writing the color value. coord.x and coord.y are considered to be unnormalized coordinates and must be in the range 0 ... image width – 1, and 0 … image height – 1.

write_imagef can only be used with image objects created with image_channel_data_type set to one of the pre-defined packed formats or set to CL_SNORM_INT8, CL_UNORM_INT8, CL_SNORM_INT16, CL_UNORM_INT16, CL_HALF_FLOAT or CL_FLOAT. Appropriate data format conversion will be done to convert channel data from a floating-point value to actual data format in which the channels are stored.

write_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, and CL_SIGNED_INT32.

write_imageui functions 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, or CL_UNSIGNED_INT32.

write_imageh functions can only be used with image objects created with image_channel_data_type set to one of the pre-defined packed formats or set to: CL_SNORM_INT8, CL_UNORM_INT8, CL_SNORM_INT16, CL_UNORM_INT16, or CL_HALF_FLOAT.

The behavior of write_imagef, write_imagei, write_imageui, write_imageh and write_imageh for image objects created with image_channel_data_type values not specified in the description above or with (x, y) coordinate values that are not in the range (0 … image width - 1, 0 … image height - 1), respectively, is undefined.

For write_imagef, write_imagei, and write_imageui forms that take image2d_t and which are enabled by the cl_khr_mipmap_image extension

Write color value to location specified by coord.xy in the mip-level specified by lod in the 2D image object specified by image. Appropriate data format conversion to the specified image format is done before writing the color value. coord.x and coord.y are considered to be unnormalized coordinates and must be in the range 0 ... image width of mip-level specified by lod – 1, and 0 ... image height of miplevel specified by lod – 1.

For write_imagef, write_imagei, write_imageh, and write_imageui forms that take image2d_array_t

Write color value to location specified by coord.xy in the 2D image identified by coord.z in the 2D image array specified specified by image. Appropriate data format conversion to the specified image format is done before writing the color value. coord.x, coord.y and coord.z are considered to be unnormalized coordinates and must be in the range 0 … image width – 1, and 0… image height – 1, and 0 … image number of layers – 1.

write_imagef can only be used with image objects created with image_channel_data_type set to one of the pre-defined packed formats or set to CL_SNORM_INT8, CL_UNORM_INT8, CL_SNORM_INT16, CL_UNORM_INT16, CL_HALF_FLOAT or CL_FLOAT. Appropriate data format conversion will be done to convert channel data from a floating-point value to actual data format in which the channels are stored.

write_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, and CL_SIGNED_INT32.

write_imageui functions 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, or CL_UNSIGNED_INT32.

write_imageh functions can only be used with image objects created with image_channel_data_type set to one of the pre-defined packed formats or set to: CL_SNORM_INT8, CL_UNORM_INT8, CL_SNORM_INT16, CL_UNORM_INT16, or CL_HALF_FLOAT.

The behavior of write_imagef, write_imagei, write_imageui, and write_imageh for image objects created with image_channel_data_type values not specified in the description above or with (x, y, z) coordinate values that are not in the range (0 … image width - 1, 0 … image height - 1, 0 … image number of layers - 1; ), respectively, is undefined.

For write_imagef, write_imagei, and write_imageui forms that take image2d_array_t and which are enabled by the cl_khr_mipmap_image extension

Write color value to location specified by coord.xy in the 2D image identified by coord.z and mip-level lod in the 2D image array specified by image. Appropriate data format conversion to the specified image format is done before writing the color value. coord.x, coord.y and coord.z are considered to be unnormalized coordinates and must be in the range 0 ... image width of the mip-level specified by lod – 1, 0 ... image height – 1 specified by lod – 1 and 0 ... image number of layers – 1

For write_imagef forms that take image2d_depth_t

Write depth value to location specified by coord.xy in the 2D depth image object specified by image. Appropriate data format conversion to the specified image format is done before writing the depth value. coord.x and coord.y are considered to be unnormalized coordinates and must be in the range 0 … image width – 1, and 0… image height – 1.

write_imagef can only be used with image objects created with image_channel_data_type set to CL_UNORM_INT16, CL_UNORM_INT24, or CL_FLOAT. Appropriate data format conversion will be done to convert depth value from a floating-point value to actual data format in which the channels are stored.

The behavior of write_imagef for image objects created with image_channel_data_type values not specified in the description above or with (x, y) coordinate values that are not in the range (0 … image width - 1, 0 … image height - 1), respectively, is undefined.

For write_imagef forms that take image2d_depth_t and which are enabled by the cl_khr_mipmap_image extension

Write color value to location specified by coord.xy in the mip-level specified by lod in the 2D image object specified by image. Appropriate data format conversion to the specified image format is done before writing the color value. coord.x and coord.y are considered to be unnormalized coordinates and must be in the range 0 ... image width of mip-level specified by lod – 1, and 0 ... image height of miplevel specified by lod – 1.

For write_imagef forms that take image2d_array_depth_t

Write depth value to location specified by coord.xy in the 2D image identified by coord.z in the 2D depth image array specified by image. Appropriate data format conversion to the specified image format is done before writing the depth value. coord.x, coord.y and coord.z are considered to be unnormalized coordinates and must be in the range 0 … image width – 1, 0… image height – 1 and 0… image number of layers – 1.

write_imagef can only be used with image objects created with image_channel_data_type set to CL_UNORM_INT16, CL_UNORM_INT24, or CL_FLOAT. Appropriate data format conversion will be done to convert depth value from a floating-point value to actual data format associated with the image..

The behavior of write_imagef write_imagei and write_imageui for image objects created with image_channel_data_type values not specified in the description above or with (x, y, z) coordinate values that are not in the range (0 … image width - 1, 0 … image height - 1, 0 … image number of layers - 1; ), respectively, is undefined.

For write_imagef forms that take image2d_array_depth_t and which are enabled by the cl_khr_mipmap_image extension

Write color value to location specified by coord.xy in the 2D image identified by coord.z and mip-level lod in the 2D image array specified by image. Appropriate data format conversion to the specified image format is done before writing the color value. coord.x, coord.y and coord.z are considered to be unnormalized coordinates and must be in the range 0 ... image width of the mip-level specified by lod – 1, 0 ... image height – 1 specified by lod – 1 and 0 ... image number of layers – 1.

For HALF forms

An application that wants to use half and halfn types will need to include the #pragma OPENCL EXTENSION cl_khr_fp16 : enable directive.

Mipmap read image functions:

For the forms that take an image2d_t object, use the coordinate coord.xy to do an element lookup in the mip-level specified by lod in the 2D image object specified by image.

For the forms that use gradients, use the gradients to compute the lod and coordinate coord.xy to do an element lookup in the mip-level specified by the computed lod in the 2D image object specified by image.

For the forms that take an image2d_array_t object, use the coordinate coord.xy to do an element lookup in the 2D image identified by coord.z and mip-level specified by lod in the 2D image object specified by image.

For the forms that take an image2d_array_t object and that use gradients, use the gradients to compute the lod coordinate and coord.xy to do an element lookup in the 2D image identified by coord.z and mip-level specified by lod in the 2D image object specified by image.

When a multisample image is accessed in a kernel, the access takes one vector of integers describing which pixel to fetch and an integer corresponding to the sample numbers describing which sample within the pixel to fetch. sample identifies the sample position in the multi-sample image.

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.

Note that image writes to sRGB images are only supported if the cl_khr_srgb_image_writes extension is supported; otherwise the behavior of writing to a sRGB image is undefined.

Image memory objects that are being read by a kernel should be declared with the read_only qualifier. write_image calls to image memory objects declared with the read_only qualifier will generate a compilation error. Image memory objects that are being written to by a kernel should be declared with the write_only qualifier. read_image calls to image memory objects declared with the write_only qualifier will generate a compilation error. read_image and write_image calls to the same image memory object in a kernel are not supported. Image memory objects that are being read and written by a kernel should be declared with the read_write qualifier.

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.

sRGB Images

The built-in image read functions will perform sRGB to linear RGB conversions if the image is an sRGB image. Writing to sRGB images from a kernel is an optional extension. The cl_khr_srgb_image_writes extension will be reported in the CL_DEVICE_EXTENSIONS string if a device supports writing to sRGB images using write_imagef. clGetSupportedImageFormats will return the supported sRGB images if CL_MEM_READ_WRITE or CL_MEM_WRITE_ONLY is specified in flags argument and the device supports writing to an sRGB image. If cl_khr_srgb_image_writes is supported, the built-in image write functions will perform the linear to sRGB conversion.

Only the R, G and B components are converted from linear to sRGB and vice-versa. The alpha component is returned as is.

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.

Specification

OpenCL Specification

Also see

Image Functions, cl_khr_mipmap_image, sampler_t, cl_khr_gl_msaa_sharing

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