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1Name
2
3    MESA_pack_invert
4
5Name Strings
6
7    GL_MESA_pack_invert
8
9Contact
10
11    Brian Paul, Tungsten Graphics, Inc. (brian.paul 'at' tungstengraphics.com)
12    Keith Whitwell, Tungsten Graphics, Inc.  (keith 'at' tungstengraphics.com)
13
14Status
15
16    Shipping (Mesa 4.0.4 and later)
17
18Version
19
20    1.0
21
22Number
23
24    TBD
25
26Dependencies
27
28    OpenGL 1.0 or later is required
29    This extensions is written against the OpenGL 1.4 Specification.
30
31Overview
32
33    This extension adds a new pixel storage parameter to indicate that
34    images are to be packed in top-to-bottom order instead of OpenGL's
35    conventional bottom-to-top order.  Only pixel packing can be
36    inverted (i.e. for glReadPixels, glGetTexImage, glGetConvolutionFilter,
37    etc).
38
39    Almost all known image file formats store images in top-to-bottom
40    order.  As it is, OpenGL reads images from the frame buffer in
41    bottom-to-top order.  Thus, images usually have to be inverted before
42    writing them to a file with image I/O libraries.  This extension
43    allows images to be read such that inverting isn't needed.
44
45IP Status
46
47    None
48
49Issues
50
51    1. Should we also define UNPACK_INVERT_MESA for glDrawPixels, etc?
52
53    Resolved:  No, we're only concerned with pixel packing.  There are other
54    solutions for inverting images when using glDrawPixels (negative Y pixel
55    zoom) or glTexImage (invert the vertex T coordinates).  It would be easy
56    enough to define a complementary extension for pixel packing in the
57    future if needed.
58
59New Procedures and Functions
60
61    None
62
63New Tokens
64
65    Accepted by the <pname> parameter of PixelStorei and PixelStoref
66    and the <pname> parameter of GetIntegerv, GetFloatv, GetDoublev
67    and GetBooleanv:
68
69        PACK_INVERT_MESA                   0x8758
70
71Additions to Chapter 2 of the OpenGL 1.4 Specification (OpenGL Operation)
72
73    None
74
75Additions to Chapter 3 of the OpenGL 1.4 Specification (Rasterization)
76
77    None
78
79Additions to Chapter 4 of the OpenGL 1.4 Specification (Per-Fragment
80Operations and the Frame Buffer)
81
82    Add the following entry to table 4.4 (PixelStore parameters) on page 182:
83
84    Parameter Name       Type    Initial Value    Valid Range
85    ---------------------------------------------------------
86    PACK_INVERT_MESA     boolean     FALSE        TRUE/FALSE
87
88    In the section labeled "Placement in Client Memory" on page 184
89    insert the following text into the paragraph before the sentence
90    that starts with "If the format is RED, GREEN, BLUE...":
91
92    "The parameter PACK_INVERT_MESA controls whether the image is packed
93     in bottom-to-top order (the default) or top-to-bottom order.  Equation
94     3.8 is modified as follows:
95
96     ... the first element of the Nth row is indicated by
97
98         p + Nk,                if PACK_INVERT_MESA is false
99         p + k * (H - 1) - Nk,  if PACK_INVERT_MESA is true, where H is the
100                                image height
101    "
102
103Additions to Chapter 5 of the OpenGL 1.4 Specification (Special Functions)
104
105    None
106
107Additions to Chapter 6 of the OpenGL 1.4 Specification (State and
108State Requests)
109
110    None
111
112Additions to Appendix A of the OpenGL 1.4 Specification (Invariance)
113
114    None
115
116Additions to the AGL/GLX/WGL Specifications
117
118    None
119
120GLX Protocol
121
122    None
123
124Errors
125
126    None
127
128New State
129
130    Add the following entry to table 6.20 (Pixels) on page 235:
131
132    Get Value         Type     Get Cmd    Initial Value  Description                Sec    Attribute
133    --------------------------------------------------------------------------------------------------
134    PACK_INVERT_MESA  boolean  GetBoolean  FALSE         Value of PACK_INVERT_MESA  4.3.2  pixel-store
135
136Revision History
137
138    21 September 2002 - Initial draft
139