clGetSupportedImageFormats

Get the list of image formats supported by an OpenCL implementation.

cl_int clGetSupportedImageFormats ( cl_context context,
  cl_mem_flags flags,
  cl_mem_object_type image_type,
  cl_uint num_entries,
  cl_image_format *image_formats,
  cl_uint *num_image_formats)

Parameters

context

A valid OpenCL context on which the image object(s) will be created.

flags

A bit-field that is used to specify allocation and usage information about the image memory object being queried and is described in the table below. To get a list of supported image formats that can be read from or written to by a kernel, flags must be set to CL_MEM_READ_WRITE (get a list of images that can be read from or written to by a kernel), CL_MEM_READ_ONLY (list of images that can be read from by a kernel) or CL_MEM_WRITE_ONLY (list of images that can be written to by a kernel). To get a list of supported image formats that can be both read from and written to by a kernel, flags must be set to CL_MEM_KERNEL_READ_AND_WRITE.

cl_mem_flags Description
CL_MEM_READ_WRITE This flag specifies that the memory object will be read and written by a kernel. This is the default.
CL_MEM_WRITE_ONLY

This flag specifies that the memory object will be written but not read by a kernel.

Reading from a buffer or image object created with CL_MEM_WRITE_ONLY inside a kernel is undefined.

CL_MEM_READ_WRITE and CL_MEM_WRITE_ONLY are mutually exclusive.

CL_MEM_READ_ONLY

This flag specifies that the memory object is a read-only memory object when used inside a kernel.

Writing to a buffer or image object created with CL_MEM_READ_ONLY inside a kernel is undefined.

CL_MEM_READ_WRITE or CL_MEM_WRITE_ONLY and CL_MEM_READ_ONLY are mutually exclusive.

CL_MEM_USE_HOST_PTR

This flag is valid only if host_ptr is not NULL. If specified, it indicates that the application wants the OpenCL implementation to use memory referenced by host_ptr as the storage bits for the memory object.

OpenCL implementations are allowed to cache the buffer contents pointed to by host_ptr in device memory. This cached copy can be used when kernels are executed on a device.

The result of OpenCL commands that operate on multiple buffer objects created with the same host_ptr or overlapping host regions is considered to be undefined.

Refer to the description of the alignment rules for host_ptr for memory objects (buffer and images) created using CL_MEM_USE_HOST_PTR.

CL_MEM_ALLOC_HOST_PTR

This flag specifies that the application wants the OpenCL implementation to allocate memory from host accessible memory.

CL_MEM_ALLOC_HOST_PTR and CL_MEM_USE_HOST_PTR are mutually exclusive.

CL_MEM_COPY_HOST_PTR

This flag is valid only if host_ptr is not NULL. If specified, it indicates that the application wants the OpenCL implementation to allocate memory for the memory object and copy the data from memory referenced by host_ptr.

CL_MEM_COPY_HOST_PTR and CL_MEM_USE_HOST_PTR are mutually exclusive.

CL_MEM_COPY_HOST_PTR can be used with CL_MEM_ALLOC_HOST_PTR to initialize the contents of the cl_mem object allocated using host-accessible (e.g. PCIe) memory.

CL_MEM_HOST_WRITE_ONLY

This flag specifies that the host will only write to the memory object (using OpenCL APIs that enqueue a write or a map for write). This can be used to optimize write access from the host (e.g. enable write-combined allocations for memory objects for devices that communicate with the host over a system bus such as PCIe).

CL_MEM_HOST_READ_ONLY

This flag specifies that the host will only read the memory object (using OpenCL APIs that enqueue a read or a map for read).

CL_MEM_HOST_WRITE_ONLY and CL_MEM_HOST_READ_ONLY are mutually exclusive.

CL_MEM_HOST_NO_ACCESS

This flag specifies that the host will not read or write the memory object.

CL_MEM_HOST_WRITE_ONLY or CL_MEM_HOST_READ_ONLY and CL_MEM_HOST_NO_ACCESS are mutually exclusive.

image_type

Describes the image type and must be either CL_MEM_OBJECT_IMAGE1D, CL_MEM_OBJECT_IMAGE1D_BUFFER, CL_MEM_OBJECT_IMAGE2D, CL_MEM_OBJECT_IMAGE3D, CL_MEM_OBJECT_IMAGE1D_ARRAY or CL_MEM_OBJECT_IMAGE2D_ARRAY.

num_entries

Specifies the number of entries that can be returned in the memory location given by image_formats.

image_formats

A pointer to a memory location where the list of supported image formats are returned. Each entry describes a cl_image_format structure supported by the OpenCL implementation. If image_formats is NULL, it is ignored.

num_image_formats

The actual number of supported image formats for a specific context and values specified by flags. If num_image_formats is NULL, it is ignored.

Notes

clGetSupportedImageFormats can be used to get the list of image formats supported by an OpenCL implementation when the following information about an image memory object is specified:

  • Context
  • Image type - 1D, 2D, or 3D image, 1D image buffer, 1D or 2D image array.
  • Image object allocation information

clGetSupportedImageFormats returns a union of image formats supported by all devices in the context.

If CL_DEVICE_IMAGE_SUPPORT specified in table 4.3 (see clGetDeviceInfo) is CL_TRUE, the values assigned to CL_DEVICE_MAX_READ_IMAGE_ARGS, CL_DEVICE_MAX_WRITE_IMAGE_ARGS, CL_DEVICE_IMAGE2D_MAX_WIDTH, CL_DEVICE_IMAGE2D_MAX_HEIGHT, CL_DEVICE_IMAGE3D_MAX_WIDTH, CL_DEVICE_IMAGE3D_MAX_HEIGHT, CL_DEVICE_IMAGE3D_MAX_DEPTH and CL_DEVICE_MAX_SAMPLERS by the implementation must be greater than or equal to the minimum values specified in table 4.3 (see clGetDeviceInfo).

Minimum List of Supported Image Formats

For 1D, 1D image from buffer, 2D, 3D image objects, 1D and 2D image array objects, the mandated minimum list of image formats that must be supported by all devices (that can be read from or written to by a kernel but not both) that support images is described in the table below (Table 5.8a):

num_channels

channel_order

channel_data_type

read/write

1

CL_R

CL_UNORM_INT8
CL_UNORM_INT16
CL_SNORM_INT8
CL_SNORM_INT16

CL_SIGNED_INT8
CL_SIGNED_INT16
CL_SIGNED_INT32
CL_UNSIGNED_INT8
CL_UNSIGNED_INT16
CL_UNSIGNED_INT32

CL_HALF_FLOAT
CL_FLOAT

read+write

1

CL_DEPTH

CL_UNORM_INT16
CL_FLOAT

read+write

2

CL_RG

CL_UNORM_INT8
CL_UNORM_INT16
CL_SNORM_INT8
CL_SNORM_INT16

CL_SIGNED_INT8
CL_SIGNED_INT16
CL_SIGNED_INT32
CL_UNSIGNED_INT8
CL_UNSIGNED_INT16
CL_UNSIGNED_INT32

CL_HALF_FLOAT
CL_FLOAT

read+write

4

CL_RGBA

CL_UNORM_INT8
CL_UNORM_INT16
CL_SNORM_INT8
CL_SNORM_INT16

CL_SIGNED_INT8
CL_SIGNED_INT16
CL_SIGNED_INT32
CL_UNSIGNED_INT8
CL_UNSIGNED_INT16
CL_UNSIGNED_INT32

CL_HALF_FLOAT
CL_FLOAT

read+write

4

CL_BGRA

CL_UNORM_INT8

read+write

4

CL_sRGBA

CL_UNORM_INT8

read+write if the cl_khr_srgb_image_writes extension is supported, else read only

1

CL_DEPTH_STENCIL

CL_UNORM_INT24
CL_FLOAT

read only (applies if the
cl_khr_gl_depth_images
extension is enabled)

For 1D, 1D image from buffer, 2D, 3D image objects, 1D and 2D image array objects, the mandated minimum list of image formats that must be supported by all devices (that can be read from and written to by a kernel) that support images is described in the table below (Table 5.8b):

num_channels

channel_order

channel_data_type

1

CL_R

CL_UNORM_INT8
CL_SIGNED_INT8
CL_SIGNED_INT16
CL_SIGNED_INT32
CL_UNSIGNED_INT8
CL_UNSIGNED_INT16
CL_UNSIGNED_INT32
CL_HALF_FLOAT
CL_FLOAT

4

CL_RGBA

CL_UNORM_INT8
CL_UNORM_INT16
CL_SIGNED_INT8
CL_SIGNED_INT16
CL_SIGNED_INT32
CL_UNSIGNED_INT8
CL_UNSIGNED_INT16
CL_UNSIGNED_INT32
CL_HALF_FLOAT
CL_FLOAT

1

CL_DEPTH_STENCIL (applies if the
cl_khr_gl_depth_images
extension is enabled)

CL_UNORM_INT24
CL_FLOAT

Additional notes if the cl_khr_gl_depth_images extension is enabled:

For the image format given by channel order of CL_DEPTH_STENCIL and channel data type of CL_UNORM_INT24, the depth is stored as an unsigned normalized 24-bit value.

For the image format given by channel order of CL DEPTH_STENCIL and channel data type of CL_FLOAT, each pixel is two 32-bit values. The depth is stored as a single precision floating point value followed by the stencil which is stored as a 8-bit integer value.

The stencil value cannot be read or written using the read_imagef and write_imagef built-in functions in an OpenCL kernel.

Depth image objects with an image channel order = CL_DEPTH_STENCIL cannot be used as arguments to clEnqueueReadImage, clEnqueueWriteImage, clEnqueueCopyImage, clEnqueueCopyImageToBuffer, clEnqueueCopyBufferToImage, clEnqueueMapImage and clEnqueueFillImage and will return a CL_INVALID_OPERATION error.

Errors

Returns CL_SUCCESS if the function is executed successfully. Otherwise, it returns one of the following errors:

  • CL_INVALID_CONTEXT if context is not a valid context.
  • CL_INVALID_VALUE if flags or image_type are not valid, or if num_entries is 0 and image_formats is not NULL.
  • CL_OUT_OF_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device.
  • CL_OUT_OF_HOST_MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.

Specification

OpenCL Specification

Also see

cl_image_format, clGetDeviceInfo

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