cl_image_desc.adoc

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cl_image_desc

The image descriptor structure describes the type and dimensions of the image or image array and is defined as:

                        typedef struct _cl_image_desc {
          cl_mem_object_type image_type;
          size_t image_width;
          size_t image_height;
          size_t image_depth;
          size_t image_array_size;
          size_t image_row_pitch;
          size_t image_slice_pitch;
          cl_uint num_mip_levels;
          cl_uint num_samples;
          cl_mem buffer;
} cl_image_desc;

Members

image_type

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

image_width

The width of the image in pixels. For a 2D image and image array, the image width must be a value >= 1 and ≤ CL_DEVICE_IMAGE2D_MAX_WIDTH. For a 3D image, the image width must be a value ≥ 1 and ≤ CL_DEVICE_IMAGE3D_MAX_WIDTH. For a 1D image buffer, the image width must be a value ≥ 1 and ≤ CL_DEVICE_IMAGE_MAX_BUFFER_SIZE. For a 1D image and 1D image array, the image width must be a value ≥ 1 and ≤ CL_DEVICE_IMAGE2D_MAX_WIDTH.

image_height

The height of the image in pixels. This is only used if the image is a 2D or 3D image, or a 2D image array. For a 2D image or image array, the image height must be a value ≥ 1 and ≤ CL_DEVICE_IMAGE2D_MAX_HEIGHT. For a 3D image, the image height must be a value ≥ 1 and ≤ CL_DEVICE_IMAGE3D_MAX_HEIGHT.

image_depth

The depth of the image in pixels. This is only used if the image is a 3D image and must be a value ≥ 1 and ≤ CL_DEVICE_IMAGE3D_MAX_DEPTH.

image_array_size

The number of images in the image array. This is only used if the image is a 1D or 2D image array. The values for image_array_size, if specified, must be a value ≥ 1 and ≤ CL_DEVICE_IMAGE_MAX_ARRAY_SIZE.

Note that reading and writing 2D image arrays from a kernel with image_array_size = 1 may be lower performance than 2D images.

image_row_pitch

The scan-line pitch in bytes. This must be 0 if host_ptr is NULL and can be either 0 or ≥ image_width * size of element in bytes if host_ptr is not NULL. If host_ptr is not NULL and image_row_pitch = 0, image_row_pitch is calculated as image_width * size of element in bytes. If image_row_pitch is not 0, it must be a multiple of the image element size in bytes. For a 2D image created from a buffer, the pitch specified (or computed if pitch specified is 0) must be a multiple of the maximum of the CL_DEVICE_IMAGE_PITCH_ALIGNMENT value for all devices in the context associated with image_desc→mem_object and that support images.

image_slice_pitch

The size in bytes of each 2D slice in the 3D image or the size in bytes of each image in a 1D or 2D image array. This must be 0 if host_ptr is NULL. If host_ptr is not NULL, image_slice_pitch can be either 0 or ≥ image_row_pitch * image_height for a 2D image array or 3D image and can be either 0 or ≥ image_row_pitch for a 1D image array. If host_ptr is not NULL and image_slice_pitch = 0, image_slice_pitch is calculated as image_row_pitch * image_height for a 2D image array or 3D image and image_row_pitch for a 1D image array. If image_slice_pitch is not 0, it must be a multiple of the image_row_pitch.

num_mip_levelnum_samples

Must be 0.

mem_object

Refers to a valid buffer or image memory object. mem_object can be a buffer memory object if image_type is CL_MEM_OBJECT_IMAGE1D_BUFFER or CL_MEM_OBJECT_IMAGE2D (To create a 2D image from a buffer object that share the data store between the image and buffer object) . mem_object can be a image object if image_type is CL_MEM_OBJECT_IMAGE2D (To create an image object from another image object that share the data store between these image objects). Otherwise it must be NULL. The image pixels are taken from the memory object’s data store. When the contents of the specified memory object’s data store are modified, those changes are reflected in the contents of the image object and vice-versa at corresponding sychronization points. For a 1D image buffer object, the image_width * size of element in bytes must be ≤ size of buffer object data store. For a 2D image created from a buffer, the image_row_pitch * image_height must be ≤ size of buffer object data store. For an image object created from another image object, the values specified in the image descriptor except for mem_object must match the image descriptor information associated with mem_object.

Note

Concurrent reading from, writing to and copying between both a buffer object and 1D image buffer or 2D image object associated with the buffer object is undefined. Only reading from both a buffer object and 1D image buffer or 2D image object associated with the buffer object is defined.

Writing to an image created from a buffer and then reading from this buffer in a kernel even if appropriate synchronization operations (such as a barrier) are performed between the writes and reads is undefined. Similarly, writing to the buffer and reading from the image created from this buffer with appropriate synchronization between the writes and reads is undefined.

Also see

cl_image_format

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