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gfx/angle/extensions/ANGLE_pack_reverse_row_order.txt@6474c204b198 (annotated)

gfx/angle/extensions/ANGLE_pack_reverse_row_order.txt

Wed, 31 Dec 2014 06:09:35 +0100

author

Michael Schloh von Bennewitz <michael@schloh.com>

date

Wed, 31 Dec 2014 06:09:35 +0100

changeset 0

6474c204b198

permissions

-rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

michael@0	1	Name
michael@0	2
michael@0	3	ANGLE_pack_reverse_row_order
michael@0	4
michael@0	5	Name Strings
michael@0	6
michael@0	7	GL_ANGLE_pack_reverse_row_order
michael@0	8
michael@0	9	Contact
michael@0	10
michael@0	11	Daniel Koch, TransGaming (daniel 'at' transgaming.com)
michael@0	12
michael@0	13	Contributors
michael@0	14
michael@0	15	Brian Salomon
michael@0	16	Daniel Koch
michael@0	17
michael@0	18	Status
michael@0	19
michael@0	20	Implemented in ANGLE ES2
michael@0	21
michael@0	22	Version
michael@0	23
michael@0	24	Last Modified Date: February 22, 2011
michael@0	25	Author Revision: 22
michael@0	26
michael@0	27	Number
michael@0	28
michael@0	29	OpenGL ES Extension #110
michael@0	30
michael@0	31	Dependencies
michael@0	32
michael@0	33	OpenGL 1.5 or OpenGL ES 1.0 are required.
michael@0	34
michael@0	35	Some of the functionality of this extension is not supported
michael@0	36	when implemented against OpenGL ES.
michael@0	37
michael@0	38	EXT_texture_rg interacts with this extension.
michael@0	39
michael@0	40	The extension is written against the OpenGL 3.2 Specification
michael@0	41	(Core Profile).
michael@0	42
michael@0	43	Overview
michael@0	44
michael@0	45	This extension introduces a mechanism to allow reversing the order
michael@0	46	in which image rows are written into a pack destination. This
michael@0	47	effectively allows an application to flip the results of a ReadPixels
michael@0	48	in the y direction operation without having to render upside down.
michael@0	49
michael@0	50	The coordinate system of OpenGL is vertically reversed in comparison to a
michael@0	51	number of other graphics systems such as native windowing APIs. Applications
michael@0	52	that perform ReadPixels may have to either render to an intermediate color
michael@0	53	buffer before calling ReadPixels or perform a flip in software after
michael@0	54	ReadPixels. In some systems the GL can perform the row reversal during
michael@0	55	ReadPixels without incurring additional cost.
michael@0	56
michael@0	57	IP Status
michael@0	58
michael@0	59	No known IP claims.
michael@0	60
michael@0	61	New Procedures and Functions
michael@0	62
michael@0	63	None
michael@0	64
michael@0	65	New Types
michael@0	66
michael@0	67	None
michael@0	68
michael@0	69	New Tokens
michael@0	70
michael@0	71	Accepted by the <pname> parameter of PixelStore{if}, GetIntegerv(),
michael@0	72	GetBooleanv(), and GetFloatv():
michael@0	73
michael@0	74	PACK_REVERSE_ROW_ORDER_ANGLE 0x93A4
michael@0	75
michael@0	76	Additions to Chapter 3 of the OpenGL 3.2 Specification (Rasterization)
michael@0	77
michael@0	78	In Section 4.3.1 (Reading Pixels) add a row to table 4.7:
michael@0	79
michael@0	80	+------------------------------+---------+---------------+-------------+
michael@0	81	| Parameter Name | Type | Initial Value | Valid Range |
michael@0	82	+------------------------------+---------+---------------+-------------+
michael@0	83	| PACK_REVERSE_ROW_ORDER_ANGLE | boolean | FALSE | TRUE/FALSE |
michael@0	84	+------------------------------+---------+---------------+-------------+
michael@0	85
michael@0	86	In Section 4.3.1 (Reading Pixels) modify the second paragraph of subsection
michael@0	87	"Placement in Pixel Pack Buffer or Client Memory" to read:
michael@0	88
michael@0	89	When PACK_REVERSE_ROW_ORDER_ANGLE is FALSE groups of elements are placed
michael@0	90	in memory just as they are taken from memory when transferring pixel
michael@0	91	rectangles to the GL. That is, the ith group of the jth row
michael@0	92	(corresponding to the ith pixel in the jth row) is placed in memory just
michael@0	93	where the ith group of the jth row would be taken from when transferring
michael@0	94	pixels. See Unpacking under section 3.7.2. The only difference is that
michael@0	95	the storage mode parameters whose names begin with PACK_ are used
michael@0	96	instead of those whose names begin with UNPACK_. If the format is RED,
michael@0	97	GREEN, BLUE, or ALPHA, only the corresponding single element is written.
michael@0	98	Likewise if the format is RG, RGB, or BGR, only the corresponding two or
michael@0	99	three elements are written. Otherwise all the elements of each group are
michael@0	100	written. When PACK_REVERSE_ROW_ORDER_ANGLE is TRUE the order of the rows
michael@0	101	of elements is reversed before the data is packed. That is, the element
michael@0	102	corresponding to pixel (x, y + height - 1) becomes the first element
michael@0	103	packed, followed by (x + 1, y + height - 1), etc. Otherwise, pixel data
michael@0	104	is packed in the same manner as when PACK_REVERSE_ROW_ORDER_ANGLE is
michael@0	105	FALSE.
michael@0	106
michael@0	107	Additions to Chapter 6 of the OpenGL 3.2 Specification (State and State Requests)
michael@0	108
michael@0	109	In Section 6.1.4 add the following sentence to the fifth paragraph
michael@0	110	(beginning with "For three-dimensional and two-dimensional array
michael@0	111	textures..."):
michael@0	112	When PACK_REVERSE_ROW_ORDER_ANGLE is TRUE the order of rows within
michael@0	113	each image are reversed without reordering the images themselves.
michael@0	114
michael@0	115	Dependencies on OpenGL ES
michael@0	116
michael@0	117	If implemented for OpenGL ES, this extension behaves as specified, except:
michael@0	118
michael@0	119	-Delete all references to formats RED, GREEN, BLUE, RG, and BGR.
michael@0	120
michael@0	121	-The language about image order in Section 6.1.4 does not apply as OpenGL ES
michael@0	122	does not have GetTexImage.
michael@0	123
michael@0	124	Dependencies on EXT_texture_rg
michael@0	125
michael@0	126	If EXT_texture_rg is present reinsert language about formats RED and RG
michael@0	127	into the OpenGL ES 2.0 specification.
michael@0	128
michael@0	129	Errors
michael@0	130
michael@0	131	None
michael@0	132
michael@0	133	New State
michael@0	134	Initial
michael@0	135	Get Value Type Get Command Value Description Sec.
michael@0	136	--------- ---- ----------- ------- ----------- ----
michael@0	137	PACK_REVERSE_ROW_ORDER_ANGLE B GetIntegerv FALSE Pixel pack row order reversal 4.3.1
michael@0	138
michael@0	139	New Implementation Dependent State
michael@0	140
michael@0	141	None
michael@0	142
michael@0	143	Issues
michael@0	144
michael@0	145	None
michael@0	146
michael@0	147	Sample Code
michael@0	148
michael@0	149	/* Allocate space to hold the pixel data */
michael@0	150	const GLvoid* pixels = malloc(width * height * 4);
michael@0	151
michael@0	152	/* Bind the framebuffer object to be read */
michael@0	153	glBindFramebuffer(GL_READ_FRAMEBUFFER, framebuffer);
michael@0	154
michael@0	155	/* Enable row order reversal */
michael@0	156	glPixelStore(GL_PACK_REVERSE_ROW_ORDER_ANGLE, TRUE);
michael@0	157
michael@0	158	/* The pixel data stored in pixels will be in top-down order, ready for
michael@0	159	* use with a windowing system API that expects this order.
michael@0	160	*/
michael@0	161	glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
michael@0	162
michael@0	163	Revision History
michael@0	164
michael@0	165	Revision 1, 2011/11/22 (Brian Salomon)
michael@0	166	- First version
michael@0	167	Revision 2, 2012/02/22 (dgkoch)
michael@0	168	- prepare for publishing