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,...]]    [opacity=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,...] [required]
           Name of input file(s)

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

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

       output=name [required]
           Name for output file

       output_mask=name
           Name for output mask file

       width=integer [required]
           Image width

       height=integer [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 composition)  built-in,  or
       would  use  the  system’s graphics API to perform composition (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)

       Accessed: unknown

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       © 2003-2022 GRASS Development Team, GRASS GIS 7.8.7 Reference Manual