image read/write routines

[etienne grossmann]

  Hello,

  I have some functions taking images as input, in which I don't know
in advance whether I will get RGB or graylevel images.

  One way is to pass an extra argument to specify the image
type. However, I don't like multiplying the arguments to my
functions. So I store images in a structure -say "X"- with fields : 

X.im : H x W   matrix for graylevel images
       H x 3W  matrix for   rgb     images, stored as [r1,g1,b1,..,gW,bW]

X.rgb : 0 or 1 : indicates whether image is RGB or graylevel

X.maxval : The maximal value of elements in X.im.


  Wrapping up slightly modified (copyright unchanged) versions Ariel
Tankus's image functions, I have small library with the following
functions :

Ariel Tankus's image functions (manipulate matrices) :
---------------------------------------------------------
writefi        writefi(fname, im)
writegif       writegif(fname, im)
writegraygif   writegraygif(fname, im)
writejpg       writejpg(fname, im)
writegrayjpg   writegrayjpg(fname, im)
writepgm       writepgm(fname, im)
writegrayps    writegrayps(fname, im, dpi)
writepnm       writepnm(fname, im, isPpm)
writeppm       writeppm(fname, im)
readfi         im = readfi(fname)
readgif        [im, isPpm,maxval] = readgif(fname)
readpnm        [im, isPpm] = readpnm(fname)
readgrayjpg    im = readgrayjpg(fname)
readjpg        [im, isPpm] = readjpg(fname)
readimagefile  [im, isPpm, maxval] = readimagefile(fname, force_gray)
getmagicnum    Copyright (C) 1998 Ariel Tankus
mergeppm       im = mergeppm(r, g, b)
splitppm       [r g b] = splitppm(im)

New functions (manipulate structures)
----------------------------------------
ims_load       ims = ims_load ( imfile ) - Load an image, returning a sructure
ims_save       ok = ims_save (ims, file [, fmt])
ims_show       ims = ims_show ( im [, pix] )
ims_size       [h,w] = ims_size (im) - Returns the size, in pixels of the image.
test_ims       Check whether ims functions work as they should
is_ims         ok = is_ims (ims) 
set_viewer     vc2 = set_viewer( [vc] )
rgb2gray       gr = rgb2gray( rgb ) - convert rgb to graylevel.
gray2rgb       rgb = gray2rgb( gr ) - convert graylevel to rgb

Needed utilities :
------------------
struct         s = struct(key1,val1,...)
getNonComment  Copyright (C) 1998 Ariel Tankus
filename_ext   ext = filename_ext( fname )


  If anyone is interested, I have put these functions (html tree and
tarball) at :

http://anonimo.isr.ist.utl.pt:8080/~etienne/octave/index.html

  Cheers,
  
  Etienne



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