0,0 → 1,204 |
Name |
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MESA_ycbcr_texture |
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Name Strings |
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GL_MESA_ycbcr_texture |
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Contact |
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Brian Paul, Tungsten Graphics, Inc. (brian.paul 'at' tungstengraphics.com) |
Keith Whitwell, Tungsten Graphics, Inc. (keith 'at' tungstengraphics.com) |
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Status |
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Shipping (Mesa 4.0.4 and later) |
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Version |
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1.0 |
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Number |
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TBD |
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Dependencies |
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OpenGL 1.0 or later is required |
This extension is written against the OpenGL 1.4 Specification. |
NV_texture_rectangle effects the definition of this extension. |
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Overview |
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This extension supports texture images stored in the YCbCr format. |
There is no support for converting YCbCr images to RGB or vice versa |
during pixel transfer. The texture's YCbCr colors are converted to |
RGB during texture sampling, after-which, all the usual per-fragment |
operations take place. Only 2D texture images are supported (not |
glDrawPixels, glReadPixels, etc). |
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A YCbCr pixel (texel) is a 16-bit unsigned short with two components. |
The first component is luminance (Y). For pixels in even-numbered |
image columns, the second component is Cb. For pixels in odd-numbered |
image columns, the second component is Cr. If one were to convert the |
data to RGB one would need to examine two pixels from columns N and N+1 |
(where N is even) to deduce the RGB color. |
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IP Status |
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None |
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Issues |
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None |
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New Procedures and Functions |
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None |
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New Tokens |
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Accepted by the <internalFormat> and <format> parameters of |
TexImage2D and TexSubImage2D: |
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YCBCR_MESA 0x8757 |
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Accepted by the <type> parameter of TexImage2D and TexSubImage2D: |
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UNSIGNED_SHORT_8_8_MESA 0x85BA /* same as Apple's */ |
UNSIGNED_SHORT_8_8_REV_MESA 0x85BB /* same as Apple's */ |
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Additions to Chapter 2 of the OpenGL 1.4 Specification (OpenGL Operation) |
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None |
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Additions to Chapter 3 of the OpenGL 1.4 Specification (Rasterization) |
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In section 3.6.4, Rasterization of Pixel Rectangles, on page 101, |
add the following to Table 3.8 (Packed pixel formats): |
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type Parameter GL Data Number of Matching |
Token Name Type Components Pixel Formats |
-------------- ------- ---------- ------------- |
UNSIGNED_SHORT_8_8_MESA ushort 2 YCBCR_MESA |
UNSIGNED_SHORT_8_8_REV_MESA ushort 2 YCBCR_MESA |
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In section 3.6.4, Rasterization of Pixel Rectangles, on page 102, |
add the following to Table 3.10 (UNSIGNED_SHORT formats): |
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UNSIGNED_SHORT_8_8_MESA: |
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15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 |
+-------------------------------+-------------------------------+ |
| 1st | 2nd | |
+-------------------------------+-------------------------------+ |
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UNSIGNED_SHORT_8_8_REV_MESA: |
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15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 |
+-------------------------------+-------------------------------+ |
| 2nd | 1st | |
+-------------------------------+-------------------------------+ |
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In section 3.6.4, Rasterization of Pixel Rectangles, on page 104, |
add the following to Table 3.12 (Packed pixel field assignments): |
|
First Second Third Fourth |
Format Element Element Element Element |
------ ------- ------- ------- ------- |
YCBCR_MESA luminance chroma |
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In section 3.8.1, Texture Image Specification, on page 125, add |
another item to the list of TexImage2D and TexImage3D equivalence |
exceptions: |
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* The value of internalformat and format may be YCBCR_MESA to |
indicate that the image data is in YCbCr format. type must |
be either UNSIGNED_SHORT_8_8_MESA or UNSIGNED_SHORT_8_8_REV_MESA |
as seen in tables 3.8 and 3.10. Table 3.12 describes the mapping |
between Y and Cb/Cr to the components. |
If NV_texture_rectangle is supported target may also be |
TEXTURE_RECTANGLE_NV or PROXY_TEXTURE_RECTANGLE_NV. |
All pixel transfer operations are bypassed. The texture is stored as |
YCbCr, not RGB. Queries of the texture's red, green and blue component |
sizes will return zero. The YCbCr colors are converted to RGB during |
texture sampling using an implementation dependent conversion. |
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In section 3.8.1, Texture Image Specification, on page 126, add |
another item to the list of TexImage1D and TexImage2D equivalence |
exceptions: |
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* The value of internalformat and format can not be YCBCR_MESA. |
|
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In section 3.8.2, Alternate Texture Image Specification Commands, on |
page 129, insert this paragraph after the first full paragraph on the |
page: |
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"If the internal storage format of the image being updated by |
TexSubImage2D is YCBCR_MESA then format must be YCBCR_MESA. |
The error INVALID_OPERATION will be generated otherwise." |
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Additions to Chapter 4 of the OpenGL 1.4 Specification (Per-Fragment |
Operations and the Frame Buffer) |
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None |
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Additions to Chapter 5 of the OpenGL 1.4 Specification (Special Functions) |
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None |
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Additions to Chapter 6 of the OpenGL 1.4 Specification (State and |
State Requests) |
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None |
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Additions to Appendix A of the OpenGL 1.4 Specification (Invariance) |
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None |
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Additions to the AGL/GLX/WGL Specifications |
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None |
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GLX Protocol |
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None |
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Errors |
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INVALID_ENUM is generated by TexImage2D if <internalFormat> is |
MESA_YCBCR but <format> is not MESA_YCBCR. |
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INVALID_ENUM is generated by TexImage2D if <format> is MESA_YCBCR but |
<internalFormat> is not MESA_YCBCR. |
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INVALID_VALUE is generated by TexImage2D if <format> is MESA_YCBCR and |
<internalFormat> is MESA_YCBCR and <border> is not zero. |
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INVALID_OPERATION is generated by TexSubImage2D if the internal image |
format is YCBCR_MESA and <format> is not YCBCR_MESA. |
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INVALID_OPERATION is generated by CopyTexSubImage2D if the internal |
image is YCBCR_MESA. |
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New State |
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Edit table 6.16 on page 231: change the type of TEXTURE_INTERNAL_FORMAT |
from n x Z42 to n x Z43 to indicate that internal format may also be |
YCBCR_MESA. |
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Revision History |
|
20 September 2002 - Initial draft |
29 April 2003 - minor updates |
3 September 2003 - further clarify when YCbCr->RGB conversion takes place |
19 September 2003 - a few more updates prior to submitting to extension |
registry. |
3 April 2004 - fix assorted inaccuracies |