Oyranos Color Management System API - Version 0.9.6
Extending Oyranos

Oyranos modules writing

Note known object types, like oyCMM_s or oyCMMapi4_s, are linked to their according documention. All others are still internal data structures, which might get exported in future versions of Oyranos.

Writing C Modules for Oyranos

Oyranos modules can be filters, plug-ins, backends, CMMs or meta modules. The API design can be seen in the Backend Modules page. To start with a module use the example code from the src/examples/oyranos_cmm_dFil.c file. Change the header, e.g. "My name" string. Select a four byte identifier for the new module and define it in CMM_NICK. The comment above CMM_NICK describes how the module library and the xxxx_cmm_module data structure (vtable) interact. Oyranos will search the appropriate path for libraries and will try to dlopen the oyCMM_s xxxx_cmm_module data structure. It therefore parses the library file name and takes the four bytes before "_cmm_module" as the modules identifier. The "xxxx_cmm_module" symbol will be searched and if found the information form there will be used to access the module functions and data. E.G. Oyranos will on Linux dlopen a module library name of "liboyranos_lcm2_cmm_module.so" and search for a "lcm2_cmm_module" symbol. CMM_NICK is defined as "lcm2" in this module.

If you choose your four byte identifier, substitute every occurence of "dFil" with the new identifier.

In the OY_DUMMY_FILTER_REGISTRATION macro the "my_filter" name should be changed to something appropriate for the new module. Oyranos users will use primarily this name to select the module. A description on how a module Registration string is to be build and how it works can be found at the end of the Detailed Description section on Backend Modules. All occurences of "my_filter" in the file should be substituted accordingly.

The old function dFilGetText should be adapted to provide the new appropriate names, copyrights and a help texts on how to use the module. Go through all functions and adapt them to the filter needs. The dFilFilterPlug_MyFilterRun function is the core of the module. It contains the processing part or algorythm. Typically a filter contains two connectors, a plug and a socket. The connectors describe their capabilities and according to this Oyranos can check in advance if two filters fit each to the other.

The oyCMMapi4_s holds most static informations of the module. It can be used to provide a processing context. A context is use in case it is very expensive to compute such a context like in ICC CMMs for color conversions and the context shall be chached by Oyranos. The oyCMMapi7_s holds the dFilFilterPlug_MyFilterRun function and the plugs and sockets.

Compile and install the module library to see if Oyranos detects it correctly. Use the test2 application therefore. It is in the source tree compiled through the "make check" shell command. The shell command to run is "test2 'CMMS list'". The test run will list all detected meta modules and the modules loaded by a meta module. The filters are sorted by their provided APIs. The test2 command might be substituted by a dedicated module utility in the future. As external checker use oyranos-xforms-modules -l.

Writing Device Modules for Oyranos

For monitor devices exist a simple abstraction layer to hook a display system in. Please read Monitor Backend Modules.

To start with a module use the src/examples/oyranos_cmm_dDev.c file and modify it. Please follow the Writing C Modules for Oyranos subsection. The parts which differ are that instead of oyCMMapi4_s the oyCMMapi8_s will be implemented. The dDevConfigs_FromPattern (oyCMMapi8_s::oyConfigs_FromPattern) is a function to call into the device module and create new oyConfig_s object(s). The dDevConfigs_Modify (oyCMMapi8_s::oyConfigs_Modify) function can use the same protocol with the difference, that it works on existing oyConfig_s object(s). The "device_name" option should be ignored by dDevConfigs_Modify. The dDev_rank_map (oyCMMapi8_s::rank_map) tells how each option shall be wighted by Oyranos to select a profile from the Oyranos DB independent from the device module. The calls into dDevConfigs_FromPattern and oyConfigs_Modify are string based. The option "command" will contain the command name the device module shall act upon.

The oyCMMapi8_s::registration string needs in its oyFILTER_REG_APPLICATION section a starting "config.icc_profile." followed by the device class name and separated by point '.' the the module nick. This convention shall enshure a proper mechanism is available to select the desired config domains from several ones.

All "dDev" occurences in the source code need to be substituted by the modules own four byte identifier.

To test the device module use oyDeviceAskProfile(), oyDeviceGetInfo() and oyDeviceGet():

oyConfig_s * device = 0; /* initialise with zero to avoid errors */
oyProfile_s * profile = 0;
oyOptions_s * options = 0; /* not used in this example */
char * text = 0;
/* Call into the device modules oyCMMapi8_s::oyConfigs_FromPattern
* function with the "list" command.
* "monitor" is to be exchanged by the actual device class and
* ":0.0" by the actual device nick name.
int error = oyDeviceGet( 0, "monitor", ":0.0", options, &device );
/* obtain a expensive list of key/value pairs from the device module */
error = oyDeviceGetInfo( device, oyNAME_DESCRIPTION, 0, &text,
malloc );
/* assign a profile to the device/driver */
error = oyDeviceSetProfile( device, "some_real_profile_in_your_path.icc" );
/* Ask Oyranos to lookup its DB for a matching profile. It is only useful
* if a profile is already set for the devices keys. The set devices can be
* viewed at the command line with:
* kdb ls user/org/freedesktop/openicc/device/config.icc_profile.*
error = oyDeviceAskProfile( device, &profile );

It is useful to step through the code. Oyranos provides the –enable-debug configure option to aid debugging and stepping through. To build the module add the -g compiler option.

The protocal on how the modules communicate with the core and the front end is described in the device_protocol_1.