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g.pnmcomp(1)		    GRASS GIS User's Manual		  g.pnmcomp(1)

NAME
       g.pnmcomp  - Overlays multiple PPM image	files.

KEYWORDS
       general,	display

SYNOPSIS
       g.pnmcomp
       g.pnmcomp --help
       g.pnmcomp    input=name[,name,...]    [mask=name[,name,...]]	[opac-
       ity=float[,float,...]]  output=name  [output_mask=name]	 width=integer
       height=integer	[bgcolor=name]	  [--overwrite]	 [--help]  [--verbose]
       [--quiet]  [--ui]

   Flags:
       --overwrite
	   Allow output	files to overwrite existing files

       --help
	   Print usage summary

       --verbose
	   Verbose module output

       --quiet
	   Quiet module	output

       --ui
	   Force launching GUI dialog

   Parameters:
       input=name[,name,...]A [required]
	   Name	of input file(s)

       mask=name[,name,...]
	   Name	of input mask file(s)

       opacity=float[,float,...]
	   Layer opacities

       output=nameA [required]
	   Name	for output file

       output_mask=name
	   Name	for output mask	file

       width=integerA [required]
	   Image width

       height=integerA [required]
	   Image height

       bgcolor=name
	   Background color
	   Either a standard color name	or R:G:B triplet

DESCRIPTION
       g.pnmcomp isn't meant for end users. It's an internal tool for  use  by
       wxGUI.

       In  essence,  g.pnmcomp generates a PPM image by	overlaying a series of
       PPM/PGM pairs (PPM = RGB	image, PGM = alpha channel).

NOTES
       The intention is	that d.* modules will emit PPM/PGM pairs  (by  way  of
       the  PNG-driver	code  being  integrated	into Display Library). The GUI
       will manage a set of layers; each layer consists	of the data  necessary
       to  generate  a	PPM/PGM	 pair.	Whenever the layer "stack" changes (by
       adding, removing, hiding, showing or re-ordering	layers), the GUI  will
       render  any  layers for which it	doesn't	already	have the PPM/PGM pair,
       then re-run g.pnmcomp to	generate the final  image  (just  redoing  the
       composition is a	lot faster than	redrawing everything).

       A C/C++ GUI would either	have g.pnmcomp's functionality (image composi-
       tion) built-in, or would	use the	system's graphics API to perform  com-
       position	 (for  translucent layers, you would need OpenGL or the	Render
       extension, or something else which supports translucent rendering).

       Tk doesn't support transparent (masked)	true-colour  images  (it  does
       support	transparent  GIFs,  but	that's limited to 256 colours),	and an
       image composition routine in Tcl	would be unacceptably slow, hence  the
       existence of g.pnmcomp.

SEE ALSO
	g.cairocomp

AUTHOR
       Glynn Clements

SOURCE CODE
       Available at: g.pnmcomp source code (history)

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       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.5 Reference	Manual

GRASS 7.8.5							  g.pnmcomp(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | SEE ALSO | AUTHOR | SOURCE CODE

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