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<?xml version="1.0"?>
<extension href="WEBGL_compressed_texture_s3tc_srgb/">
<name>WEBGL_compressed_texture_s3tc_srgb</name>
<contact>
<a href="https://www.khronos.org/webgl/public-mailing-list/">WebGL working group</a> (public_webgl 'at' khronos.org)
</contact>
<contributors>
<contributor>Members of the WebGL working group</contributor>
</contributors>
<number>32</number>
<depends>
<api version="1.0"/>
</depends>
<overview>
<p>
This extension exposes the sRGB compressed texture formats defined in the
EXT_texture_sRGB</a> OpenGL extension to WebGL.
</p>
<features>
<feature>
Compression formats <code>COMPRESSED_SRGB_S3TC_DXT1_EXT</code>,
<code>COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT</code>, <code>COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT</code>, and
<code>COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT</code> may be passed to
the <code>compressedTexImage2D</code> and <code>compressedTexSubImage2D</code> entry points.
</feature>
<feature>
Calling <code>getParameter</code> with the argument <code>COMPRESSED_TEXTURE_FORMATS</code>
will include the 4 formats from this specification.
</feature>
<feature>
<p>The following format specific restrictions must be enforced:</p>
<dl>
<dt>COMPRESSED_SRGB_S3TC_DXT1_EXT</dt>
<dt>COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT</dt>
<dd><p>The <code>byteLength</code> of the ArrayBufferView, <code>pixels</code>, passed to
either <code>compressedTexImage2D</code> or <code>compressedTexSubImage2D</code>
must match the following equation:</p>
<blockquote><code>
floor((width + 3) / 4) * floor((height + 3) / 4) * 8
</code></blockquote>
<p>
If it is not an <code>INVALID_VALUE</code> error is generated.
</p>
<p>When <code>level</code> equals zero <code>width</code> and <code>height</code>
must be a multiple of 4. When <code>level</code> is greater than 0 <code>width</code>
and <code>height</code> must be 0, 1, 2 or a multiple of 4.</p>
<p>
If they are not an <code>INVALID_OPERATION</code> error is generated.
</p>
<p>
For <code>compressedTexSubImage2D</code> <code>xoffset</code> and
<code>yoffset</code> must be a multiple of 4 and
<code>width</code> must be a multiple of 4 or equal to the original
width of the <code>level</code>. <code>height</code> must be a multiple of 4 or
equal to the original height of the <code>level</code>.
If they are not an <code>INVALID_OPERATION</code> error is generated.
</p>
</dd>
<dt>COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT</dt>
<dt>COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT</dt>
<dd><p>The <code>byteLength</code> of the ArrayBufferView, <code>pixels</code>, passed to
either <code>compressedTexImage2D</code> or <code>compressedTexSubImage2D</code> must
match the following equation:</p>
<blockquote><code>
floor((width + 3) / 4) * floor((height + 3) / 4) * 16
</code></blockquote>
<p>
If it is not an <code>INVALID_VALUE</code> error is generated.
</p>
<p>When <code>level</code> equals zero <code>width</code> and <code>height</code>
must be a multiple of 4. When <code>level</code> is greater than 0 <code>width</code>
and <code>height</code> must be 0, 1, 2 or a multiple of 4.</p>
<p>
If they are not an <code>INVALID_OPERATION</code> error is generated.
</p>
<p>
For <code>compressedTexSubImage2D</code> <code>xoffset</code> and
<code>yoffset</code> must be a multiple of 4 and
<code>width</code> must be a multiple of 4 or equal to the original
width of the <code>level</code>. <code>height</code> must be a multiple of 4 or
equal to the original height of the <code>level</code>.
If they are not an <code>INVALID_OPERATION</code> error is generated.
</p>
</dd>
</dl>
</feature>
</features>
</overview>
<idl xml:space="preserve">
[NoInterfaceObject]
interface WEBGL_compressed_texture_s3tc_srgb {
/* Compressed Texture Formats */
const GLenum COMPRESSED_SRGB_S3TC_DXT1_EXT = 0x8C4C;
const GLenum COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT = 0x8C4D;
const GLenum COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT = 0x8C4E;
const GLenum COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT = 0x8C4F;
};
</idl>
<history>
<revision date="2016/06/10">
<change>Initial revision.</change>
</revision>
<revision date="2016/07/21">
<change>Moved to draft after discussion in working group, and study of possible dependencies.</change>
</revision>
<revision date="2017/05/31">
<change>Moved to community approved after Mozilla voiced support.</change>
</revision>
</history>
</extension>