--- /dev/null
+Name
+
+ MESA_pack_invert
+
+Name Strings
+
+ GL_MESA_pack_invert
+
+Contact
+
+ Brian Paul, Tungsten Graphics, Inc. (brian.paul 'at' tungstengraphics.com)
+ Keith Whitwell, Tungsten Graphics, Inc. (keith 'at' tungstengraphics.com)
+
+Status
+
+ Shipping (Mesa 4.0.4 and later)
+
+Version
+
+ 1.0
+
+Number
+
+ TBD
+
+Dependencies
+
+ OpenGL 1.0 or later is required
+ This extensions is written against the OpenGL 1.4 Specification.
+
+Overview
+
+ This extension adds a new pixel storage parameter to indicate that
+ images are to be packed in top-to-bottom order instead of OpenGL's
+ conventional bottom-to-top order. Only pixel packing can be
+ inverted (i.e. for glReadPixels, glGetTexImage, glGetConvolutionFilter,
+ etc).
+
+ Almost all known image file formats store images in top-to-bottom
+ order. As it is, OpenGL reads images from the frame buffer in
+ bottom-to-top order. Thus, images usually have to be inverted before
+ writing them to a file with image I/O libraries. This extension
+ allows images to be read such that inverting isn't needed.
+
+IP Status
+
+ None
+
+Issues
+
+ 1. Should we also define UNPACK_INVERT_MESA for glDrawPixels, etc?
+
+ Resolved: No, we're only concerned with pixel packing. There are other
+ solutions for inverting images when using glDrawPixels (negative Y pixel
+ zoom) or glTexImage (invert the vertex T coordinates). It would be easy
+ enough to define a complementary extension for pixel packing in the
+ future if needed.
+
+New Procedures and Functions
+
+ None
+
+New Tokens
+
+ Accepted by the <pname> parameter of PixelStorei and PixelStoref
+ and the <pname> parameter of GetIntegerv, GetFloatv, GetDoublev
+ and GetBooleanv:
+
+ PACK_INVERT_MESA 0x8758
+
+Additions to Chapter 2 of the OpenGL 1.4 Specification (OpenGL Operation)
+
+ None
+
+Additions to Chapter 3 of the OpenGL 1.4 Specification (Rasterization)
+
+ None
+
+Additions to Chapter 4 of the OpenGL 1.4 Specification (Per-Fragment
+Operations and the Frame Buffer)
+
+ Add the following entry to table 4.4 (PixelStore parameters) on page 182:
+
+ Parameter Name Type Initial Value Valid Range
+ ---------------------------------------------------------
+ PACK_INVERT_MESA boolean FALSE TRUE/FALSE
+
+ In the section labeled "Placement in Client Memory" on page 184
+ insert the following text into the paragraph before the sentence
+ that starts with "If the format is RED, GREEN, BLUE...":
+
+ "The parameter PACK_INVERT_MESA controls whether the image is packed
+ in bottom-to-top order (the default) or top-to-bottom order. Equation
+ 3.8 is modified as follows:
+
+ ... the first element of the Nth row is indicated by
+
+ p + Nk, if PACK_INVERT_MESA is false
+ p + k * (H - 1) - Nk, if PACK_INVERT_MESA is true, where H is the
+ image height
+ "
+
+Additions to Chapter 5 of the OpenGL 1.4 Specification (Special Functions)
+
+ None
+
+Additions to Chapter 6 of the OpenGL 1.4 Specification (State and
+State Requests)
+
+ None
+
+Additions to Appendix A of the OpenGL 1.4 Specification (Invariance)
+
+ None
+
+Additions to the AGL/GLX/WGL Specifications
+
+ None
+
+GLX Protocol
+
+ None
+
+Errors
+
+ None
+
+New State
+
+ Add the following entry to table 6.20 (Pixels) on page 235:
+
+ Get Value Type Get Cmd Initial Value Description Sec Attribute
+ --------------------------------------------------------------------------------------------------
+ PACK_INVERT_MESA boolean GetBoolean FALSE Value of PACK_INVERT_MESA 4.3.2 pixel-store
+
+Revision History
+
+ 21 September 2002 - Initial draft
projects / mesa.git / blobdiff