WRITE_IMAGE2D(3clc)

✨ NAME ✨

write_image — bestie, this one writes a color value to a location in a 2D image object 💖

Like, that's the whole job. Here are the eight (8) glow-ups of it:

void write_imagef(image2d_t image, int2 coord, float4 color);

void write_imagef(image2d_array_t image, int4 coord, float4 color);

void write_imagei(image2d_t image, int2 coord, int4 color);

void write_imagei(image2d_array_t image, int4 coord, int4 color);

void write_imageui(image2d_t image, int2 coord, uint4 color);

void write_imageui(image2d_array_t image, int4 coord, uint4 color);

void write_imageh(image2d_t image, int2 coord, half4 color);

void write_imageh(image2d_array_t image, int4 coord, half4 color);

This is WRITE_IMAGE (2D), from the OpenCL Manual (the 3clc corner of the internet, iykyk) 🦋

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🌸 DESCRIPTION 🌸

Okay so, vibe check first: each of these lil functions has ✨opinions✨ about which image it'll even talk to. Let's go one by one, no skipping, I promise.

💅 write_imagef

write_imagef can only be used with image objects created with image_channel_data_type set to one of the pre-defined packed formats, or set to one of:

• CL_SNORM_INT8
• CL_UNORM_INT8
• CL_SNORM_INT16
• CL_UNORM_INT16
• CL_HALF_FLOAT
• CL_FLOAT

Appropriate data format conversion will be done to convert channel data from a floating-point value to the actual data format in which the channels are stored. So like, it translates for you, it's giving considerate 💅

💜 write_imagei

write_imagei can only be used with image objects created with image_channel_data_type set to one of these:

• CL_SIGNED_INT8
• CL_SIGNED_INT16
• CL_SIGNED_INT32

🩵 write_imageui

write_imageui functions can only be used with image objects created with image_channel_data_type set to one of these:

• CL_UNSIGNED_INT8
• CL_UNSIGNED_INT16
• CL_UNSIGNED_INT32

🧚 half and halfn girlies, listen up

An application that wants to use half and halfn types will need to include the

#pragma OPENCL EXTENSION cl_khr_fp16(3clc) : enable

directive. Don't forget it, bestie, or nothing works and we'll all be sad 😭

🎀 write_imageh

write_imageh can only be used with image objects created with image_channel_data_type set to one of the pre-defined packed formats, or set to:

• CL_SNORM_INT8
• CL_UNORM_INT8
• CL_SNORM_INT16
• CL_UNORM_INT16
• CL_HALF_FLOAT

🫶 Functions that take image2d_t

Functions that take image2d_t.PP For the functions that take an image_2d_t image, write the color value to the location specified by coord.xy in the 2D image object specified by image. Appropriate data format conversion to the specified image format is done before writing the color value.

coord.x and coord.y are considered to be unnormalized coordinates and must be in the range 0 ... image width - 1, and 0 ... image height - 1. That's the range. Stay in it. 👑

💀 the undefined behavior part (read this, fr fr)

For functions that take image_2d_t, the behavior of write_imagef, write_imagei, write_imageui, and write_imageh is undefined for image objects created with image_channel_data_type values not specified in the description above, or with (x, y) coordinate values that are not in the range (0 ... image width - 1, 0 ... image height - 1), respectively.

Not "it might be fine." Not "it usually works." Undefined. That means the spec is not promising you anything at all. Do not roll those dice, bestie 💀

🌈 Functions that take image2d_array_t

Functions that take image2d_array_t.PP For the functions that take an image_2d_array_t image, write the color value to the location specified by coord.xy in the 2D image identified by coord.z in the 2D image array specified by image. Appropriate data format conversion to the specified image format is done before writing the color value.

coord.x, coord.y and coord.z are considered to be unnormalized coordinates and must be in the range 0 ... image width - 1, 0 ... image height - 1 and 0 ... image number of layers - 1.

💀 the undefined behavior part, but with a z coordinate

For functions that take image_2d_array_t, the behavior of write_imagef, write_imagei, write_imageui, and write_imageh is undefined for image objects created with image_channel_data_type values not specified in the description above, or with (x, y, z) coordinate values that are not in the range (0 ... image width - 1, 0 ... image height - 1), respectively.

Same energy. Undefined is undefined. Periodt. 🎀

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📝 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.

Now the rules, and they're strict but fair:

• Image memory objects that are being read by a kernel should be declared with the accessQualifiers(3clc) qualifier.
• write_image calls to image memory objects declared with the accessQualifiers(3clc) qualifier will generate a compilation error.
• Image memory objects that are being written to by a kernel should be declared with the accessQualifiers(3clc) qualifier.
• read_image calls to image memory objects declared with the accessQualifiers(3clc) qualifier will generate a compilation error.
• read_image and write_image calls to the same image memory object in a kernel are not supported. 🙈

The read_image calls return 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. So like, x y z w = red green blue alpha. Cute, memorable, slay ✨

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📚 SPECIFICATION 📚

OpenCL Specification[1]

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👀 SEE ALSO 👀

• imageFunctions(3clc)

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✍️ AUTHORS ✍️

The Khronos Group

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©️ 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 condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.

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🔖 NOTES 🔖

1. OpenCL Specification — page 292, section 6.12.14 - Image Read and Write Functions

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and that's the whole page, bestie 🫶 brought to you by The Khronos Group, dated 01/14/2021. go forth and write pixels responsibly, mwah 💅✨