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Diffstat (limited to 'mesalib/docs/MESA_pack_invert.spec')
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diff --git a/mesalib/docs/MESA_pack_invert.spec b/mesalib/docs/MESA_pack_invert.spec new file mode 100644 index 000000000..53d5fca71 --- /dev/null +++ b/mesalib/docs/MESA_pack_invert.spec @@ -0,0 +1,138 @@ +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 defined 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 |