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%LOADPPM Load a PPM image
%
% I = loadppm(filename)
%
% Returns a matrix containing the image loaded from the PPM format
% file filename. Handles ASCII (P3) and binary (P6) PPM file formats.
%
% If the filename has no extension, and open fails, a '.ppm' and
% '.pnm' extension will be tried.
%
% SEE ALSO: saveppm loadpgm
%
% Copyright (c) Peter Corke, 1999 Machine Vision Toolbox for Matlab
% Peter Corke 1994
function I = loadppm(file)
white = [' ' 9 10 13]; % space, tab, lf, cr
white = setstr(white);
fid = fopen(file, 'r');
if fid < 0,
fid = fopen([file '.ppm'], 'r');
end
if fid < 0,
fid = fopen([file '.pnm'], 'r');
end
if fid < 0,
error('Couldn''t open file');
end
magic = fread(fid, 2, 'char');
while 1
c = fread(fid,1,'char');
if c == '#',
fgetl(fid);
elseif ~any(c == white)
fseek(fid, -1, 'cof'); % unputc()
break;
end
end
cols = fscanf(fid, '%d', 1);
while 1
c = fread(fid,1,'char');
if c == '#',
fgetl(fid);
elseif ~any(c == white)
fseek(fid, -1, 'cof'); % unputc()
break;
end
end
rows = fscanf(fid, '%d', 1);
while 1
c = fread(fid,1,'char');
if c == '#',
fgetl(fid);
elseif ~any(c == white)
fseek(fid, -1, 'cof'); % unputc()
break;
end
end
maxval = fscanf(fid, '%d', 1);
while 1
c = fread(fid,1,'char');
if c == '#',
fgetl(fid);
elseif ~any(c == white)
fseek(fid, -1, 'cof'); % unputc()
break;
end
end
if magic(1) == 'P',
if magic(2) == '3',
%disp(['ASCII PPM file ' num2str(rows) ' x ' num2str(cols)])
I = fscanf(fid, '%d', [cols*3 rows]);
elseif magic(2) == '6',
%disp(['Binary PPM file ' num2str(rows) ' x ' num2str(cols)])
if maxval == 1,
fmt = 'unint1';
elseif maxval == 15,
fmt = 'uint4';
elseif maxval == 255,
fmt = 'uint8';
elseif maxval == 2^32-1,
fmt = 'uint32';
end
I = fread(fid, [cols*3 rows], fmt);
else
disp('Not a PPM file');
end
end
%
% now the matrix has interleaved columns of R, G, B
%
I = I';
size(I);
R = I(:,1:3:(cols*3));
G = I(:,2:3:(cols*3));
B = I(:,3:3:(cols*3));
fclose(fid);
I = zeros(rows,cols,3);
I(:,:,1) = R;
I(:,:,2) = G;
I(:,:,3) = B;
I = uint8(I);
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