rgbpix: buffered write un production

Modules/README.md

@@ -1,8 +1,5 @@
 # General purpose modules
 
-## Compiler un module
-
-Mmmmm...
 
 ## Modules disponibles
 
@@ -13,7 +10,9 @@ Write gray level 2d buffer (aka picture) to disk in the NetPNM format.
 
 ### pixrgb
 
-Write 8 bits RGB pictures to PNM format.
+Write 8 bits or 16 bits RGB pictures to PNM format.
+
+**Warning!** The width of the picture MUST be a multiple of 4 !
 
 ### trials
 
@@ -21,8 +20,16 @@ Experimental WIPs from hell.
 
 ### dummy
 
-A "do nothing" useless module. But you cas use it to fool an optimizing
-compiler, or have a sane place to put a breakpoint with gdb
+A "do nothing" useless module.
+But you cas use it to fool an optimizing compiler,
+or have a sane place to put a breakpoint with gdb
+
+## Compiler un module
+
+You can use the same options as for a main program.
+And when you use the module, you have to specify the paths
+for the .mod and the .o to the linker.
+See [Makefile](./Makefile) for an example.
 
 ## TODO