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)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual