clEnqueueWriteImage

Enqueues a command to write from a 2D or 3D image object to host memory.

cl_int clEnqueueWriteImage ( cl_command_queue command_queue,
  cl_mem image,
  cl_bool blocking_write,
  const size_t origin[3],
  const size_t region[3],
  size_t input_row_pitch,
  size_t input_slice_pitch,
  const void * ptr,
  cl_uint num_events_in_wait_list,
  const cl_event *event_wait_list,
  cl_event *event)

Parameters

command_queue

Refers to the command-queue in which the write command will be queued. command_queue and image must be created with the same OpenCL contex

image

Refers to a valid 2D or 3D image object.

blocking_write

Indicates if the write operation is blocking or non-blocking.

If blocking_write is CL_TRUE the OpenCL implementation copies the data referred to by ptr and enqueues the write command in the command-queue. The memory pointed to by ptr can be reused by the application after the clEnqueueWriteImage call returns.

If blocking_write is CL_FALSE the OpenCL implementation will use ptr to perform a nonblocking write. As the write is non-blocking the implementation can return immediately. The memory pointed to by ptr cannot be reused by the application after the call returns. The event argument returns an event object which can be used to query the execution status of the write command. When the write command has completed, the memory pointed to by ptr can then be reused by the application.

origin

Defines the (x, y, z) offset in pixels in the image from where to write or write. If image is a 2D image object, the z value given by origin[2] must be 0.

region

Defines the (width, height, depth) in pixels of the 2D or 3D rectangle being write or written. If image is a 2D image object, the depth value given by region[2] must be 1.

input_row_pitch

The length of each row in bytes. This value must be greater than or equal to the element size in bytes * width. If input_row_pitch is set to 0, the appropriate row pitch is calculated based on the size of each element in bytes multiplied by width.

input_slice_pitch

Size in bytes of the 2D slice of the 3D region of a 3D image being written. This must be 0 if image is a 2D image. This value must be greater than or equal to row_pitch * height. If input_slice_pitch is set to 0, the appropriate slice pitch is calculated based on the row_pitch * height.

ptr

The pointer to a buffer in host memory where image data is to be written to.

event_wait_list , num_events_in_wait_list

Specify events that need to complete before this particular command can be executed. If event_wait_list is NULL, then this particular command does not wait on any event to complete. If event_wait_list is NULL, num_events_in_wait_list must be 0. If event_wait_list is not NULL, the list of events pointed to by event_wait_list must be valid and num_events_in_wait_list must be greater than 0. The events specified in event_wait_list act as synchronization points. The context associated with events in event_wait_list and command_queue must be the same.

event

Returns an event object that identifies this particular write command and can be used to query or queue a wait for this particular command to complete. event can be NULL in which case it will not be possible for the application to query the status of this command or queue a wait for this command to complete.

Notes

Calling clEnqueueWriteImage to update the latest bits in a region of the image object with the ptr argument value set to host_ptr + (origin[2] * image slice pitch + origin[1] * image row pitch + origin[0] * bytes per pixel), where host_ptr is a pointer to the memory region specified when the image object being written is created with CL_MEM_USE_HOST_PTR, must meet the following requirements in order to avoid undefined behavior:

  • The host memory region being written contains the latest bits when the enqueued write command begins execution.
  • The input_row_pitch and input_slice_pitch argument values in clEnqueueWriteImage must be set to the image row pitch and slice pitch.
  • The image object is not mapped.
  • The image object is not used by any command-queue until the write command has finished execution.

Errors

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

  • CL_INVALID_COMMAND_QUEUE if command_queue is not a valid command-queue.
  • CL_INVALID_CONTEXT if the context associated with command_queue and image are not the same or if the context associated with command_queue and events in event_wait_list are not the same.
  • CL_INVALID_MEM_OBJECT if image is not a valid image object.
  • CL_INVALID_VALUE if the region being write or written specified by origin and region is out of bounds or if ptr is a NULL value.
  • CL_INVALID_VALUE if image is a 2D image object and origin[2] is not equal to 0 or region[2] is not equal to 1 or slice_pitch is not equal to 0.
  • CL_INVALID_EVENT_WAIT_LIST if event_wait_list is NULL and num_events_in_wait_list greater than 0, or event_wait_list is not NULL and num_events_in_wait_list is 0, or if event objects in event_wait_list are not valid events.
  • CL_MEM_OBJECT_ALLOCATION_FAILURE if there is a failure to allocate memory for data store associated with image.
  • 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

clEnqueueReadImage, clEnqueueCopyImage

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