write_image1d

Write color value to location in a 1D image object.

void write_imagef ( image1d_t  image ,
  int  coord ,
  float4  color )
void write_imagef ( image1d_buffer_t  image ,
  int  coord ,
  float4  color )
void write_imagef ( image1d_array_t  image ,
  int2  coord ,
  float4  color )
void write_imagei ( image1d_t  image ,
  int  coord ,
  int4  color )
void write_imagei ( image1d_buffer_t  image ,
  int  coord ,
  int4  color )
void write_imagei ( image1d_array_t  image ,
  int2  coord ,
  int4  color )
void write_imageui ( image1d_t  image ,
  int  coord ,
  uint4  color )
void write_imageui ( image1d_buffer_t  image ,
  int  coord ,
  uint4  color )
void write_imageui ( image1d_array_t  image ,
  int2  coord ,
  uint4  color )

Functions added with half precision support enabled by extension cl_khr_fp16:

void write_imageh ( image1d_t  image ,
  int  coord ,
  half4  color )
void write_imageh ( image1d_buffer_t  image ,
  int  coord ,
  half4  color )
void write_imageh ( image1d_array_t  image ,
  int2  coord ,
  half4  color )

Functions added with mipmap support enabled by extension cl_khr_mipmap_image:

void write_imagef ( image1d_t  image ,
  int  coord ,
  int  lod ,
  float4  color )
void write_imagei ( image1d_t  image ,
  int  coord ,
  int  lod ,
  int4  color )
void write_imageui ( image1d_t  image ,
  int  coord ,
  int  lod ,
  uint4  color )
void write_imagef ( image1d_array_t  image ,
  int2  coord ,
  int  lod ,
  float4  color )
void write_imagei ( image1d_array_t  image ,
  int2  coord ,
  int  lod ,
  int4  color )
void write_imageui ( image1d_array_t  image ,
  int2  coord ,
  int  lod ,
  uint4  color )

Description

For write_imagef, write_imagei, and write_imageui forms that take image1d_t or image1d_buffer_t

:

Write color value to location specified by coord in the 1D image or 1D image buffer object specified by image. Appropriate data format conversion to the specified image format is done before writing the color value. coord is considered to be unnormalized coordinates and must be in the range 0 ... image width – 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 functions 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.

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.

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 coordinate values that is not in the range (0 … image width - 1), is undefined.

For write_imagef, write_imagei, and write_imageui forms that take image1d_array_t

:

Write color value to location specified by coord.x in the 1D image identified by coord.y in the 1D image array 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 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 functions 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.

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.

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) coordinate values that are not in the range (0 … image width - 1, 0 …image number of layers - 1), respectively, is undefined.

For write_imageh

:

The write_imageh functions are enabled when the half type is supported and 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. Appropriate data format conversion to the specified image format is done before writing the color value. x & y are considered to be unnormalized coordinates and must be in the range 0 ... width – 1, and 0 … height – 1.

Mipmap write image functions enabled by cl_khr_mipmap_image:

For the image write 1D functions enabled by the mipmap extension that take an image1d_t object, write color value to location specified by coord in the mip-level specified by lod in the 1D image object specified by image. Appropriate data format conversion to the specified image format is done before writing the color value. coord is considered to be an unnormalized coordinate and must be in the range 0… image width of the mip-level specified by lod – 1.

In these functions, the behavior of write_imagef, write_imagei, and write_imageui if the coordinate value is not in the range (0… image width of the mip-level specified by lod – 1) or lod value exceeds the (number of mip-levels in the image – 1) is undefined.

For the image write 1D functions enabled by the mipmap extension that take an image1d_array_t object, write color value to location specified by coord.x in the 1D image specified by coord.y and mip-level lod in the 1D image array 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 number of layers - 1.

In these functions, the behavior of write_imagef, write_imagei, and write_imageui if (x, y) coordinate values are not in the range (0… image width of the mip-level specified by lod – 1, 0… image number of layers – 1), respectively or lod value exceeds the (number of mip-levels in the image – 1), is 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.

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.

Mapping image channels to color values

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, CL_sRGB, CL_sRGBx (r, g, b, 1.0)
CL_RGBA, CL_BGRA, CL_ARGB, CL_ABGR, CL_sRGBA, CL_sBGRA (r, g, b, a)
CL_INTENSITY (I, I, I, I)
CL_LUMINANCE (L, L, L, 1.0)

For CL_DEPTH images, a scalar value is returned by read_imagef or supplied to write_imagef.

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.

CL_SAMPLER_NORMALIZED_COORDS must be CL_TRUE for built-in functions described in the table above that read from a mip-mapped image; otherwise the behavior is undefined. The value specified in the lod argument is clamped to the minimum of (actual number of mip-levels – 1) in the image or value specified for CL_SAMPLER_LOD_MAX.

Specification

OpenCL Specification

Also see

Image Functions, cl_khr_mipmap_image, sampler_t

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