pnm                  package:pixmap                  R Documentation

_R_e_a_d/_W_r_i_t_e _P_o_r_t_a_b_l_e _A_n_y_m_a_p _I_m_a_g_e_s

_D_e_s_c_r_i_p_t_i_o_n:

     Reading and writing of bitmap images in PBM (black/white), PGM
     (grey) and PPM (color) format.

_U_s_a_g_e:

     read.pnm(file, ...)
     write.pnm(object, file= NULL, forceplain = FALSE, type = NULL, maxval = 255)

_A_r_g_u_m_e_n_t_s:

    file: name of the pnm file.

     ...: further arguments passed to 'pixmap' (like 'bbox').

  object: an object of class '"pixmap"'.

forceplain: logical; if true, an ASCII pnm file is written. Default is
          to write a binary (raw) file.

    type: one of '"pbm"', '"pgm"' or '"ppm"'. Default is to use '"pgm"'
          for grey images and '"ppm"' for color images.

  maxval: the maximum color-component value; the default is a colour
          depth of 8 bits, i.e., the integer 255.

_D_e_t_a_i_l_s:

     'read.pnm' reads a pnm file and loads the image into an object of
     class 'pixmap'.

     'write.pnm' writes an object of class 'pixmap' to a pnm file, the
     'type' argument controls wheter the written image file is a
     black-and-white bitmap (pbm), grey (pgm) or color (ppm).

     'plot.pnm' plots a pnm object using the command 'image'. The only
     difference is that the element '[1,1]' of 'pnmobj' is plotted as
     the upper left corner (plain 'image' would plot '[1,1]' as the
     lower left corner.

_V_a_l_u_e:

     'read.pnm' returns an object of class 'pixmapRGB' for color
     pixmaps (ppm), and an object of class 'pixmapGrey' for pbm and
     pgm. Note that the _type_ of file as determined by the first two
     bytes according to pnm standards is important, _not the extension_
     of the file. In fact, the file name extension is completely
     ignored.

_A_u_t_h_o_r(_s):

     Roger Bivand and Friedrich Leisch

_S_e_e _A_l_s_o:

     'pixmap'

_E_x_a_m_p_l_e_s:

      x <- read.pnm(system.file("pictures/logo.ppm", package="pixmap")[1])
      plot(x)
      print(x)

      x <- read.pnm(system.file("pictures/logo.pgm", package="pixmap")[1])
      plot(x)

      x <- read.pnm(system.file("pictures/logo.pbm", package="pixmap")[1])
      plot(x)

