## Copyright (C) 2008-2012 John W. Eaton
## Copyright (C) 2013 Carnë Draug
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or (at
## your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn  {Function File} {} imwrite (@var{img}, @var{filename})
## @deftypefnx {Function File} {} imwrite (@var{img}, @var{filename}, @var{ext})
## @deftypefnx {Function File} {} imwrite (@var{img}, @var{map}, @var{filename})
## @deftypefnx {Function File} {} imwrite (@dots{}, @var{param1}, @var{val1}, @dots{})
## Write images in various file formats.
##
## The image @var{img} can be a binary, grayscale, RGB, or multi-dimensional
## image.  The size and class of @var{img} should be the same as what should
## be expected when reading it with @code{imread}: the 3rd and 4th dimensions
## reserved for color space, and multiple pages respectively.  If it's an
## indexed image, the colormap @var{map} must also be specified.
##
## If @var{ext} is not supplied, the file extension of @var{filename} is used
## to determine the format.  The actual supported formats are dependent on
## options made during the build of Octave.  Use @code{imformats} to check
## the support of the different image formats.
##
## Depending on the file format, it is possible to configure the writing
## of images with @var{param}, @var{val} pairs.  The following options
## are supported:
##
## @table @samp
## @item Alpha
## Alpha (transparency) channel for the image.  This must be a matrix with
## same class, and number of rows and columns of @var{img}.  In case of a
## multipage image, the size of the 4th dimension must also match and the third
## dimension must be a singleton.  By default, image will be completely
## opaque.
##
## @item Quality
## Set the quality of the compression.  The value should be an
## integer between 0 and 100, with larger values indicating higher visual
## quality and lower compression.  Defaults to 75.
##
## @item WriteMode
## Some file formats, such as TIFF and GIF, are able to store multiple
## images in a single file.  This option specifies if @var{img} should be
## appended to the file (if it exists) or if a new file should be created
## for it (possibly overwriting an existing file).  The value should be
## the string @qcode{"Overwrite"} (default), or @qcode{"Append"}.
##
## Despite this option, the most efficient method of writing a multipage
## image is to pass a 4 dimensional @var{img} to @code{imwrite}, the
## same matrix that could be expected when using @code{imread} with the
## option @qcode{"Index"} set to @qcode{"all"}.
##
## @end table
##
## @seealso{imread, imfinfo, imformats}
## @end deftypefn

function imwrite (varargin)
  if (nargin < 2)
    print_usage ();
  endif
  [filename, ext] = imwrite_filename (varargin{2:end});

  fmt = imformats (ext);
  ## When there is no match, fmt will be a 1x1 structure with
  ## no fields, so we can't just use `isempty (fmt)'.
  if (isempty (fieldnames (fmt)))
    if (isempty (ext))
      error ("imwrite: no extension found for %s to identify the image format",
             filename);
    endif
    warning ("imwrite: unlisted image format %s (see imformats). Trying to save anyway.",
             ext);
    __imwrite__ (varargin{:});
  else
    fmt.write (varargin{:});
  endif

endfunction

%% Test input validation
%!error imwrite ()                            # Wrong # of args
%!error imwrite (1)                           # Wrong # of args
%!error imwrite ({"cell"}, "filename.jpg")    # Wrong class for img
%!error imwrite (1, [], "filename.jpg")       # Empty image map
%!error imwrite (1, 2, 3)                     # No filename specified
%!error imwrite (1, "filename")               # No fmt specified
%!error imwrite (1, "filename", "junk")       # Invalid fmt specified
%!error imwrite ([], "filename.jpg")          # Empty img matrix
%!error imwrite (spones (2), "filename.jpg")  # Invalid sparse img

%!testif HAVE_MAGICK
%! imw = randi (255, 100, "uint8");
%! filename = [tmpnam() ".png"];
%! unwind_protect
%!   imwrite (imw, filename);
%!   imr = imread (filename);
%! unwind_protect_cleanup
%!   unlink (filename);
%! end_unwind_protect
%! assert (imw, imr)