| ppmwrite(arg1,arg2,arg3,arg4,arg5,arg6) |
function ppmwrite(arg1,arg2,arg3,arg4,arg5,arg6)
%PPMWRITE Write a PPM (portable pixmap) file to disk.
%
% PPMWRITE(X,MAP,'FILENAME') writes a PPM file containing the indexed
% image X and color map MAP to the file 'FILENAME'.
%
% PPMWRITE(X,MAP,'FILENAME','ENCODING') where 'ENCODING' is either
% 'ascii' (or 'plain') or 'binary' (or 'raw') lets the user specify
% whether the PPM file should be ascii or binary encoded. Default is
% 'ascii'.
%
% PPMWRITE(R,G,B,'FILENAME') writes a PPM file containing the RGB
% image in the matrices R,G,B to the file 'FILENAME'.
%
% PPMWRITE(R,G,B,'FILENAME','ENCODING') allows the user to specify the
% encoding as described above.
%
% PPMWRITE(X,MAP,'FILENAME',MAXVALUE) uses MAXVALUE as the maximum
% pixel value. This ables pixmaps with more than 256 values per color,
% since the number of possible values is MAXVALUE+1.
%
% PPMWRITE(X,MAP,'FILENAME',MAXVALUE,'ENCODING') lets the user specify
% the output encoding as described above. Binary encoded pixmaps can
% not have MAXVALUE larger than 255, so a MAXVALUE larger than 255
% will always give an ascii encoded file regardless of the specified
% output encoding.
%
% PPMWRITE(R,G,B,'FILENAME',MAXVALUE) and
% PPMWRITE(R,G,B,'FILENAME',MAXVALUE,'ENCODING') works as described
% above, but on an RGB image.
%
% The 'ascii' format is the most portable and is the only that allows
% a MAXVALUE larger than 255, so it is also the most general. The
% 'binary' format files are, however, much smaller and many times
% faster to read and write than the 'ascii' format.
%
% If file name has no suffix, '.ppm' is used.
%
% See also: PPMREAD, PBMREAD, PBMWRITE, PGMREAD, PGMWRITE.
% Author: Peter J. Acklam
% Time-stamp: 1998-04-15 21:26:33
% E-mail: jacklam@math.uio.no (Internet)
% URL: http://www.math.uio.no/~jacklam
nargs = nargin;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Check number of input arguments.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
error( nargchk( 3, 6, nargs ) );
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Identify input arguments.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if ( nargs == 3 ) % 3 input arguments
%
% PPMWRITE(X,MAP,'FILENAME')
%
X = arg1;
map = arg2;
filename = arg3;
maxval = 255;
encoding = 'ascii';
isindexed = 1;
elseif ( nargs == 6 ) % 6 input arguments
%
% PPMWRITE(R,G,B,'FILENAME',MAXVALUE,'ENCODING')
%
r = arg1;
g = arg2;
b = arg3;
filename = arg4;
maxval = arg5;
encoding = arg6;
isindexed = 0;
elseif ( nargs == 4 ) % 4 input arguments
if ( ~ischar(arg3) & ischar(arg4) )
%
% PPMWRITE(R,G,B,'FILENAME')
%
r = arg1;
g = arg2;
b = arg3;
filename = arg4;
maxval = 255;
encoding = 'ascii';
isindexed = 0;
elseif ( ischar(arg3) & ischar(arg4) )
%
% PPMWRITE(X,MAP,'FILENAME','ENCODING')
%
X = arg1;
map = arg2;
filename = arg3;
encoding = arg4;
maxval = 255;
isindexed = 1;
else
%
% PPMWRITE(X,MAP,'FILENAME',MAXVALUE)
%
X = arg1;
map = arg2;
filename = arg3;
maxval = arg4;
encoding = 'ascii';
isindexed = 1;
end
else % 5 input arguments
if ( ischar(arg4) & ischar(arg5) )
%
% PPMWRITE(R,G,B,'FILENAME','ENCODING')
%
r = arg1;
g = arg2;
b = arg3;
filename = arg4;
encoding = arg5;
maxval = 255;
isindexed = 0;
elseif ( ischar(arg4) & ~ischar(arg5) )
%
% PPMWRITE(R,G,B,'FILENAME',MAXVALUE)
%
r = arg1;
g = arg2;
b = arg3;
filename = arg4;
maxval = arg5;
encoding = 'ascii';
isindexed = 0;
else
%
% PPMWRITE(X,MAP,'FILENAME',MAXVALUE,'ENCODING')
%
X = arg1;
map = arg2;
filename = arg3;
maxval = arg4;
encoding = arg5;
isindexed = 1;
end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% These are no longer needed, so delete them to save memory.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clear arg1 arg2 arg3 arg4 arg5 arg6
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% The blocksize is the number of pixels written simultaneously.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
blocksize = 8192;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Check the size of the R,G,B matrices.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if ~isindexed
if any( size(r) ~= size(g) ) | any( size(r) ~= size(b) )
error( 'The R, G and B matrices must have the same size.' );
end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Check filename.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if ( ~ischar(filename) | isempty(filename) )
error( 'File name must be a non-empty string' );
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Add suffix to file name if necessary.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
k = [ find( filename == filesep ) ];
if isempty(k)
k = 0;
else
k = max(k);
end
if all( filename(k+1:end) ~= '.' )
filename = [ filename '.ppm' ];
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Check and simplify the encoding specification.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if ~ischar(encoding)
error( 'Encoding specification must be a string.' );
end
if any( encoding(1) == 'aApP' ) % 'ascii' (or 'plain') format.
isascii = 1;
elseif any( encoding(1) == 'bBrR' ) % 'binary' (or 'raw') format.
isascii = 0;
else
error( 'Illegal encoding specification.' );
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Maximum pixel value can not be larger than 255 with binary encoding.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if ( ~isascii & ( maxval > 255 ) )
disp( 'Warning:' );
disp( 'Maximum pixel value must be <= 255 with binary encoding.' );
disp( 'Using ascii encoding instead.' );
encoding = 'ascii';
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Maximum gray value smaller than 255 with binary encoding is not yet
% supported. :-(
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if ( ~isascii & ( maxval < 255 ) )
error( 'MAXVAL less than 255 with binary encoding not supported.' );
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Open output file for writing.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
fid = fopen( filename, 'w' );
if ( fid == -1 )
error( [ 'Can''t open file ''' filename ''' for writing.' ] );
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Get dimension of image.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if isindexed
[ rows, cols ] = size( X );
else
[ rows, cols ] = size( r );
end
pixels = rows*cols;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Write file header.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Magic number.
if isascii
magic = 'P3';
else
magic = 'P6';
end
% Write header. Use FLOOR( CLOCK ) to avoid a second value of 60.
fprintf( fid, [ ...
'%s\n', ...
'# Created by Matlab (%s) %04d-%02d-%02d %02d:%02d:%02d\n', ...
'%d %d\n', ...
'%d\n' , ...
], magic, mfilename, floor( clock ), cols, rows, maxval );
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Write image.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
pixels_written = 0;
char_count = 0;
while ( pixels_written < pixels )
first_pixel = pixels_written + 1;
last_pixel = min( pixels_written+blocksize, pixels );
pixel = (first_pixel:last_pixel)'; % Pixels counted row-wise.
row = ceil( pixel/cols ); % Row numbers.
col = pixel - cols*(row-1); % Column numbers.
pixel = row + rows*(col-1); % Pixels counted column-wise.
pixels_to_write_now = last_pixel - first_pixel + 1;
if isindexed
int = round( maxval*map(X(pixel),:) );
else
int = round( maxval*[ r(pixel) g(pixel) b(pixel) ] );
end
int = int';
int = int(:);
if isascii % Write ascii format.
for i = 1:3*pixels_to_write_now
str = sprintf( '%d', int(i) ); % Integer as string.
nstr = length( str ); % Length of string.
if ( char_count+nstr >= 70 ) % If it does not fit on line...
fprintf( fid, '\n' ); % ...add newline...
char_count = 0; % ...and reset counter...
elseif ( char_count > 0 ) % If not beginning of line...
fprintf( fid, ' ' ); % ...add blank...
char_count = char_count+1; % ...and increment counter.
end
fprintf( fid, str ); % Write string to file.
char_count = char_count+nstr; % Increment counter.
end
else % Write binary format.
fwrite( fid, int, 'uint8' ); % Write as unsigned 8 bit ints.
end
pixels_written = pixels_written + pixels_to_write_now;
end
fclose( fid ); % Close file.
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