net-color spec 0.2 ==================== DRAFT 1 Revision History ------------------ Revision 0.1 2008-07-21 Tomas Carnecky initial incomplete spec for Color Management near X Draft for Revision 0.2 2010-05-16 Kai-Uwe Behrmann clearify XcolorRegion, add references, history, date and headers, remove XRandR, _NET_COLOR_MANAGEMENT and _NET_COLOR_PROFILES from this version, add _NET_COLOR_REGIONS and _NET_COLOR_DESKTOP Introduction -------------- The net-color spec defines a protocol which can be used by X11 clients to offload color correction and transformation into the compositing manager. The basic idea is to communicate client side regions to the X11 server. The regions can of this version have no ICC profile attached, which means a color server, typical in a compositing manager, shall not color manage these regions. These regions then are in the responsibility of the application. Color Region -------------- A color region is described by the following C structure: typedef struct { uint32_t region; /* window centric XserverRegion */ uint8_t md5[16]; /* ICC MD5 hash of the associated ICC profile */ } XcolorRegion; It defines a region and the attached color profile. Color regions are attached to windows and used by the compositing manager to apply the proper color transformation. Windows can have an unlimited amount of regions attached, though only the first 2 * 2^32 can be referenced. As of this spec the md5 shall be set to zero to signal the region is already color managed by the application. Atoms ------- _NET_COLOR_REGIONS: The atom is attached to windows and lists the XcolorRegion's defined for that specific window. The application is responsible to update the contained informations, e.g. on region resize or move inside the window. The type is XA_CARDINAL and values are stored in network byte order. _NET_COLOR_TARGET: Is attached to windows and specifies on which output the window should look correctly. The type is XA_STRING. _NET_COLOR_DESKTOP: The atom is attached on the root window to tell about a color servers activity. The content is of type XA_STRING and has four sections separated by a empty space char ' '. The _NET_COLOR_DESKTOP atom is a string with following usages: - uniquely identify the colour server - tell the name of the colour server - tell the colour server is alive All sections are separated by one space char ' ' for easy parsing. The first section contains the process id (pid_t) of the color server process, which has set the atom. The second section contains time since epoch GMT as returned by time(NULL). The thired section contains the bar '|' separated and surrounded capabilities: - NCP _NET_COLOR_PROFILES - NCT _NET_COLOR_TARGET - NCM _NET_COLOR_MANAGEMENT - NCR _NET_COLOR_REGIONS - V0.3 indicates version compliance to the _ICC_Profile in X spec The fourth section contains the servers name identifier. As of this specification the third section must contain NCR and the supported _ICC_PROFILE in X version. NCT is optional. A example of a valid atom might look like: _NET_COLOR_DESKTOP(STRING) = "4518 1274001512 |NCR|V0.3| compiz_colour_desktop" References ------------ 1. X window system (hhtp://www.x.org) 2. International Color Consortium (http://www.color.org) 3. _ICC_Profile in X (http://www.freedesktop.org/wiki/Specifications/icc_profiles_in_x_spec) 4. Xcolor reference implementation (git clone git://www.oyranos.org/git/xcolor) 5. colour_deskop colour server for compiz (git clone git://www.oyranos.org/git/oyranos) 6. xcmsevents monitor tool (git clone git://www.oyranos.org/git/oyranos) Todo ------ The relation to the _ICC_Profile in X spec is undefined in that a monitor profile as provided by the _ICC_PROFILE(_xxx) atom is for unaware applications not correct during the run of the color server. Necessarily a double color conversion will happen for net-color spec unaware applications, which is a clear conflict. A _ICC_DEVICE_PROFILE(_xxx) atom during color server run is in discussion. 2008 (c) Tomas Carnecky, 2010 (c) Kai-Uwe Behrmann