Image Read and Write Functions
Built-in functions to read, write, and query image memory objects. Click an item in the table below for details about that function.
| read_imagef for 1D | Do an element lookup in the 1D image object with or without a sampler, returning floating-point values (including optional mipmap support). |
| read_image{i|ui} for 1D | Do an element lookup in the 1D image object with or without a sampler, returning unnormalized signed integer and unsigned integer values (including optional mipmap support). |
| read_imageh for 1D | OPTIONAL function to do an element lookup in the 1D image object with or without a sampler, returning floating-point values. Enabled with cl_khr_fp16. |
| write_image {f|i|ui|h} for 1D |
Write color value to location in the 2D image object (including optional mipmap support).
The half type is enabled with
cl_khr_fp16.
|
| read_imagef for 2D | Do an element lookup in the 2D image object with or without a sampler, returning floating-point values (including optional mipmap support). |
| read_image{i|ui} for 2D | Do an element lookup in the 2D image object with or without a sampler, returning unnormalized signed integer and unsigned integer values (including optional mipmap support). |
| read_imageh for 2D | OPTIONAL function to do an element lookup in the 2D image object with or without a sampler, returning floating-point values. Enabled with cl_khr_fp16. |
| write_image {f|i|ui|h} for 2D |
Write color value to location in the 2D image object (including optional mipmap support).
The half type is enabled with
cl_khr_fp16.
|
| read_imagef for 3D | Do an element lookup in the 3D image object with or without a sampler, returning floating-point values (including optional mipmap support). |
| read_image{i|ui} for 3D | Do an element lookup in the 3D image object with or without a sampler, returning unnormalized signed integer and unsigned integer values (including optional mipmap support). |
| read_imageh for 3D | OPTIONAL function to do an element lookup in the 3D image object with or without a sampler, returning floating-point values. Enabled with cl_khr_fp16. |
| write_image {f|i|ui|h} for 3D |
Write color value to location in the 2D image object (including optional mipmap support).
The half type is enabled with
cl_khr_fp16.
|
| get_image_width | Return the image width in pixels |
| get_image_height | Return the image height in pixels. |
| get_image_depth | Return the 3D image depth in pixels |
| get_image_channel_data_type | Return the image channel data type |
| get_image_channel_order | Return the image channel order |
| get_image_dim | Return the image dimensions |
| get_image_array_size | Return the number of images in an image array |
| get_image_num_mip_levels | Return the number of mip-levels. Enabled with extension cl_khr_mipmap_image |
| get_image_num_samples | Return the number of samples in the 2D MSAA image. Enabled with extension cl_khr_gl_msaa_sharing |
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.
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