function pnmwritexbm(data, map, filename, varargin)
%PNMWRITEXBM Write a XBM (X bitmap) file to disk.
%
% PNMWRITEXBM(BM, [], FILENAME) writes the bitmap image BM to the file
% specified by the string FILENAME.
%
% PNMWRITEXBM(I, [], FILENAME) converts the grayscale image I into a bitmap
% (by thresholding) and writes the resulting image to the file specified by
% the string FILENAME.
%
% PNMWRITEXBM(RGB, [], FILENAME) converts the truecolor image represented by
% the M-by-N-by-3 array RGB into a bitmap (by grayscaling and thresholding)
% and writes the resulting image to the file specified by the string
% FILENAME.
%
% PNMWRITEXBM(X, MAP, FILENAME) converts the indexed image represented by the
% index matrix X and colormap MAP into a bitmap (by grayscaling and by
% thresholding) and writes the resulting image to the file specified by the
% string FILENAME.
%
% PNMWRITEXBM(...,'XHotSpot',VAL) sets the XHotSpot value to VAL. VAL must
% be a non-negative integer.
%
% PNMWRITEXBM(...,'YHotSpot',VAL) sets the YHotSpot value to VAL. VAL must
% be a non-negative integer.
%
% See also IMREAD, IMWRITE, IMFINFO.
% Author: Peter J. Acklam
% Time-stamp: 2009-07-21 14:21:54 +02:00
% E-mail: pjacklam@online.no
% URL: http://home.online.no/~pjacklam
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Some argument checking
%
error(nargchk(3, Inf, nargin));
nd = ndims(data);
if nd > 3
error(sprintf('%d-D data not supported for XBM files', nd));
end
if ~ischar(filename) | isempty(filename)
error('Filename must be a non-empty string.');
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Process param/value pairs
%
xhotspot = [];
yhotspot = [];
paramStrings = ['xhotspot'
'yhotspot'];
if rem(length(varargin), 2)
error('Odd number of Parameter-Value arguments.');
end
for k = 1:2:length(varargin)
param = lower(varargin{k});
if ~ischar(param)
error('Parameter name must be a string');
end
idx = strmatch(param, paramStrings);
if isempty(idx)
error(sprintf('Unrecognized parameter name "%s"', param));
elseif (length(idx) > 1)
error(sprintf('Ambiguous parameter name "%s"', param));
end
param = deblank(paramStrings(idx,:));
switch param
case 'xhotspot'
xhotspot = varargin{k+1};
if ~isscalnonnegint(xhotspot)
error('XHOTSPOT must be a scalar positive integer.');
end
case 'yhotspot'
yhotspot = varargin{k+1};
if ~isscalnonnegint(yhotspot)
error('YHOTSPOT must be a scalar positive integer.');
end
end
end
[height, width, channels] = size(data);
cls = class(data);
rgbw = [ 0.298936 ; 0.587043 ; 0.114021 ]; % RGB weights
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Convert any image to a bitmap image. Afterwards, `data' should be a
% uint8 array of zeros (black) and ones (white).
%
if isempty(map)
% no colormap, so it is not an indexed image
if channels > 1
% it is an rgb image
% adjust rgb weights (to save work we convert from rgb image to
% grayscale _and_ map pixel values to the set {0,1} all in one go)
switch class(data)
case 'uint8', rgbw = rgbw / 255;
case 'uint16', rgbw = rgbw / 65535;
case 'double', % do nothing
end
% convert to uint8 array of zeros and ones
data = uint8(round( rgbw(1) * double(data(:,:,1)) ...
+ rgbw(2) * double(data(:,:,2)) ...
+ rgbw(3) * double(data(:,:,3)) ));
else
% it is a grayscale image or a bitmap image
if islogical(data)
% it is a bitmap image
% convert to zeros and ones; let all non-zero values be one
data(data) = 1;
else
% it is a grayscale image
% convert to zeros and ones by bitshifting or thresholding
switch class(data)
case 'uint8', data = bitshift(data, -7);
case 'uint16', data = uint8(bitshift(data, -15));
case 'double', data = uint8(data >= 0.5);
end
end
end
else
% it is an indexed image
% convert colormap to a vector of ones and zeros by thresholding
bwmap = uint8(map * rgbw >= 0.5);
% get image data
switch class(data)
case 'double', data = bwmap(data);
case {'uint8', 'uint16'}, data = bwmap(double(data)+1);
otherwise, error('Index array is of invalid class.');
end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Convert the bitmap image into a vector containing the integer values
% that will be written to the image file.
%
% adjust values since XBM uses zeros for white and ones for black
data = bitxor(data, 1);
% add padding if necessary
byteWidth = ceil(width/8); % number or bytes for one scanline
paddedWidth = 8*byteWidth; % padded width of image
if paddedWidth > width
data(:,width+1:paddedWidth) = 0;
end
% convert from bits (zeros and ones) to bytes {0,1,...,255} without
% temporary conversion to double
bytedata = repmat(uint8(0), [height byteWidth]);
for i = 1:8
bytedata = bitor(bytedata, bitshift(uint8(data(:,i:8:end)), i-1));
end
% Open output file for writing.
fid = fopen(filename, 'wt');
if fid < 0
error([filename ': can''t open file for writing.']);
end
% Get file basename and trim it so it is suitable as an identifier.
k = find(filename == '.');
if isempty(k)
filebase = filename;
else
filebase = filename(1:k(end)-1);
end
k = (filebase < 'a' | filebase > 'z') ...
& (filebase < 'A' | filebase > 'Z') ...
& (filebase < '0' | filebase > '9');
filebase(k) = '_';
% Write file header.
fprintf(fid, '#define %s_width %d\n', filebase, width);
fprintf(fid, '#define %s_height %d\n', filebase, height);
if ~isempty(xhotspot)
fprintf(fid, '#define %s_x_hot %d\n', filebase, xhotspot);
end
if ~isempty(yhotspot)
fprintf(fid, '#define %s_y_hot %d\n', filebase, yhotspot);
end
% Write image data. Some XBM software writes images with a header saying
% "static unsigned char ...", but some software failes to read the image
% if the word "unsigned" is present, so just write "static char ...".
bytedata = bytedata.';
fprintf(fid, 'static char %s_bits[] = {\n', filebase);
format = [repmat(' 0x%02x,', [1 12]) '\n'];
fprintf(fid, format, double(bytedata(1:end-1)));
fprintf(fid, '%02x};\n', double(bytedata(end)));
% Close file.
fclose(fid);
function tf = isscalnonnegint(x)
%ISSCALNONNEGINT True if input is a scalar non-negative integer.
tf = all(size(x) == 1) & isnumeric(x); % scalar and numeric
if ~tf, return, end
x = double(x);
tf = x == round(x) & x >= 0; % integer and positive
