octave_packages/image-1.0.15/bmpwrite.m

   1 ## -*- texinfo -*-
   2 ## @deftypefn {Function File} bmpwrite (@var{X}, @var{map}, @var{file})
   3 ## Write the bitmap @var{X} into @var{file} (8-bit indexed uncompressed).
   4 ## The values in @var{X} are indices into the given RGB colour @var{map}.
   5 ## @deftypefnx{Function File} bmpwrite (@var{X}, @var{file})
   6 ## Write the bitmap @var{X} into @var{file} (24-bit truecolor uncompressed).
   7 ## @var{X} is an m x n x 3 array of R,G,B integer values in the range 0 to 255.
   8 ## @end deftypefn
   9
  10 ## This code is in the public domain.
  11 ## Author: Paul Kienzle <pkienzle@users.sf.net>
  12
  13
  14 function bmpwrite(x,colormap_or_file,file)
  15   if nargin==2
  16      bmpwrite_truecolor(x(:,:,1),x(:,:,2),x(:,:,3),colormap_or_file);
  17   else
  18      bmpwrite_indexed(x,colormap_or_file,file);
  19   endif
  20 endfunction
  21
  22 function bmpwrite_truecolor(R,G,B,file)
  23     h = rows(R); w = columns(R);
  24     padw = ceil(3*w/4)*4-3*w;
  25     header = 14+40;
  26     filesize = header+h*(3*w+padw);
  27     arch = "ieee-le";
  28     file = fopen(file, "wb");
  29     fwrite(file,toascii("BM"),"uchar",0,arch); # file tag
  30     fwrite(file,filesize,"long",0,arch);    # length of file
  31     fwrite(file,0,"long",0,arch);           # reserved
  32     fwrite(file,header,"long",0,arch);      # offset of raster data in file
  33
  34     fwrite(file,40,"long",0,arch);          # header size
  35     fwrite(file,w,"long",0,arch);           # image width
  36     fwrite(file,h,"long",0,arch);           # image height
  37     fwrite(file,1,"short",0,arch);          # number of planes
  38     fwrite(file,24,"short",0,arch);         # pixels per plane
  39     fwrite(file,0,"long",0,arch);           # compression (none)
  40     fwrite(file,0,"long",0,arch);           # compressed size of image
  41     resolution = 72/2.54*100;               # 72 dpi / 2.54 cm/in * 100 cm/m
  42     fwrite(file,resolution,"long",0,arch);  # horizontal resolution
  43     fwrite(file,resolution,"long",0,arch);  # vertical resolution
  44     fwrite(file,0,"long",0,arch);           # number of colours used
  45     fwrite(file,0,"long",0,arch);           # number of "important" colors
  46
  47     ## raster image, lines written bottom to top.
  48     R = R(end:-1:1,:)';
  49     G = G(end:-1:1,:)';
  50     B = B(end:-1:1,:)';
  51     RGB=[B(:),G(:),R(:)]';  # Now [[B;G;R],[B;G;R],...,[B;G;R]]
  52     RGB=reshape(RGB,3*w,h); # Now [[B;G;R;...;B;G;R],...,[B;G;R;...;B;G;R]]
  53     fwrite(file,[RGB;zeros(padw,h)],"uchar",0,arch);
  54     fclose(file);
  55 endfunction
  56
  57 function bmpwrite_indexed(x,map,file)
  58
  59     if rows(map) > 256,
  60       bmpwrite_truecolor(reshape(map(x,1),size(x))*255,
  61                          reshape(map(x,2),size(x))*255,
  62                          reshape(map(x,3),size(x))*255,
  63                          file);
  64       return;
  65     endif
  66     [h,w] = size(x);
  67     padw = ceil(w/4)*4-w;
  68     header = 14+40+4*rows(map);
  69     filesize = header+(w+padw)*h;
  70     arch = "ieee-le";
  71     file = fopen(file, "wb");
  72     fwrite(file,toascii("BM"),"uchar",0,arch); # file tag
  73     fwrite(file,filesize,"long",0,arch);    # length of file
  74     fwrite(file,0,"long",0,arch);           # reserved
  75     fwrite(file,header,"long",0,arch);      # offset of raster data in file
  76
  77     fwrite(file,40,"long",0,arch);          # header size
  78     fwrite(file,w,"long",0,arch);           # image width
  79     fwrite(file,h,"long",0,arch);           # image height
  80     fwrite(file,1,"short",0,arch);          # number of planes
  81     fwrite(file,8,"short",0,arch);          # pixels per plane
  82     fwrite(file,0,"long",0,arch);           # compression (none)
  83     fwrite(file,0,"long",0,arch);           # compressed size of image
  84     resolution = 72/2.54*100;               # 72 dpi / 2.54 cm/in * 100 cm/m
  85     fwrite(file,resolution,"long",0,arch);  # horizontal resolution
  86     fwrite(file,resolution,"long",0,arch);  # vertical resolution
  87     fwrite(file,rows(map),"long",0,arch);   # number of colours used
  88     fwrite(file,0,"long",0,arch);           # number of "important" colors
  89
  90     ## colormap BGR0BGR0BGR0BGR0...
  91     map=[round(map*255), zeros(rows(map),1)];
  92     map=map(:,[3,2,1,4]);
  93     fwrite(file,map',"uchar",0,arch);
  94
  95     ## raster image, each line on a 32-bit boundary, padded with zeros
  96     ## lines written bottom to top.
  97     fwrite(file,[flipud(x-1)';zeros(padw,h)],"uchar",0,arch);
  98     fclose(file);
  99 endfunction