CLENQUEUECOPYIMAGETO(3clc)

💖 CLENQUEUECOPYIMAGETO 💖

okay bestie, sit down, hydrate, because today we're learning about clEnqueueCopyImageToBuffer from the OpenCL Manual (that's the 3clc manual, iykyk) ✨

This one does exactly what it says on the tin: it enqueues a command to copy an image object to a buffer object. Image → buffer. That's the whole vibe. 🦋

---

✨ SYNOPSIS ✨

cl_int clEnqueueCopyImageToBuffer(cl_command_queue command_queue,
                                  cl_mem src_image, cl_mem dst_buffer,
                                  const size_t *src_origin,
                                  const size_t *region,
                                  size_t dst_offset,
                                  cl_uint num_events_in_wait_list,
                                  const cl_event *event_wait_list,
                                  cl_event *event);

---

🌸 PARAMETERS 🌸

• command_queue — has to be a valid command-queue, no exceptions. And listen: the OpenCL context associated with command_queue, src_image, and dst_buffer must all be the same. They have to be in the same friend group, periodt.
• src_image — a valid image object. that's it, that's the requirement 💅
• dst_buffer — a valid buffer object. the destination, the moment, the main character.
• src_origin — this one defines the (x, y, z) offset in pixels in the 1D, 2D or 3D image, the (x, y) offset and the image index in the 2D image array, or the (x) offset and the image index in the 1D image array. Now the rules, and yes you have to follow them:
  • if src_image is a 2D image object, src_origin[2] must be 0.
  • if src_image is a 1D image or 1D image buffer object, src_origin[1] and src_origin[2] must be 0.
  • if src_image is a 1D image array object, src_origin[2] must be 0.
  • if src_image is a 1D image array object, src_origin[1] describes the image index in the 1D image array.
  • if src_image is a 2D image array object, src_origin[2] describes the image index in the 2D image array.
• region — defines the (width, height, depth) in pixels of the 1D, 2D or 3D rectangle, the (width, height) in pixels of the 2D rectangle and the number of images of a 2D image array, or the (width) in pixels of the 1D rectangle and the number of images of a 1D image array. The rules:
  • if src_image is a 2D image object, region[2] must be 1.
  • if src_image is a 1D image or 1D image buffer object, region[1] and region[2] must be 1.
  • if src_image is a 1D image array object, region[2] must be 1.
• dst_offset — the offset where you start copying data into dst_buffer. The size in bytes of the region being copied, called dst_cb, gets computed like this, and this is giving math class but make it graphics:
  • width * height * depth * bytes/image element if src_image is a 3D image object
  • width * height * bytes/image element if src_image is a 2D image
  • width * height * arraysize * bytes/image element if src_image is a 2D image array object
  • width * bytes/image element if src_image is a 1D image or 1D image buffer object
  • width * arraysize * bytes/image element if src_image is a 1D image array object
• event_wait_list, num_events_in_wait_list — these specify the events that need to complete before this particular command can even think about executing. The deets:
  • if event_wait_list is NULL, then this 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.
  • the memory associated with event_wait_list can be reused or freed after the function returns. so you can let it go, bestie 🕊️
• event — returns an event object that identifies this particular copy command and can be used to query or queue a wait for this 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. clEnqueueBarrierWithWaitList(3clc) can be used instead. And one lil gotcha: if the event_wait_list and the event arguments are not NULL, the event argument should not refer to an element of the event_wait_list array. don't do it. 💀

---

🔥 ERRORS 🔥

clEnqueueCopyImageToBuffer returns CL_SUCCESS if the function is executed successfully (slay 🎀). 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, src_image and dst_buffer 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 src_image is not a valid image object or dst_buffer is not a valid buffer object, or if src_image is a 1D image buffer object created from dst_buffer.
• CL_INVALID_VALUE if the 1D, 2D, or 3D rectangular region specified by src_origin and src_origin + region refers to a region outside src_image, or if the region specified by dst_offset and dst_offset + dst_cb refers to a region outside dst_buffer.
• CL_INVALID_VALUE if values in src_origin and region do not follow the rules described in the argument description for src_origin and region.
• CL_INVALID_EVENT_WAIT_LIST if event_wait_list is NULL and num_events_in_wait_list > 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_MISALIGNED_SUB_BUFFER_OFFSET if dst_buffer is a sub-buffer object and the offset specified when the sub-buffer object is created is not aligned to CL_DEVICE_MEM_BASE_ADDR_ALIGN value for the device associated with queue. alignment matters, no cap. 📏
• CL_INVALID_IMAGE_SIZE if image dimensions (image width, height, specified or compute row and/or slice pitch) for src_image are not supported by the device associated with queue.
• CL_INVALID_IMAGE_FORMAT if image format (image channel order and data type) for src_image are not supported by the device associated with queue.
• CL_MEM_OBJECT_ALLOCATION_FAILURE if there is a failure to allocate memory for the data store associated with src_image or dst_buffer.
• CL_INVALID_OPERATION if the device associated with command_queue does not support images (i.e. CL_DEVICE_IMAGE_SUPPORT specified in the table of OpenCL Device Queries for clGetDeviceInfo(3clc) is CL_FALSE).
• 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[1]

---

👀 SEE ALSO 👀

clEnqueueReadBuffer(3clc), clEnqueueWriteBuffer(3clc), clCreateBuffer(3clc), clEnqueueCopyBuffer(3clc), clEnqueueCopyBufferToImage(3clc)

---

👑 AUTHORS 👑

The Khronos Group

---

💜 COPYRIGHT 💜

Copyright © 2007-2011 The Khronos Group Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the following condition: the above copyright notice and this permission notice shall be included in all copies or substantial portions of the Materials.

---

🧚 NOTES 🧚

1. OpenCL Specification — page 107, section 5.3.4 - Copying between Image and Buffer Objects

---

and that's the whole page, bestie 🫶 go forth and copy your images into your buffers responsibly. this lil masterpiece came from The Khronos Group, dated 01/14/2021, from the 3clc manual. mwah 💋✨