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✏️ Editing: viewmiff.ps

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% CA 94945, U.S.A., +1(415)492-9861, for further information.
%

% viewmiff.ps
% Display a MIFF file.  You would think the 'display' command would do this,
% but many versions of 'display' either core-dump or require unacceptably
% large amounts of memory.
% FITPAGE is true, it fits the output page size to the image

% Recognize MIFF keywords.
/miffwords mark
  /class { cvn /class exch def }
  /colors { cvi /colors exch def }
  /columns { cvi /Width exch def }
  /compression { cvn /compression exch def }
  /depth { cvi /depth exch def }
  /packets { cvi /packets exch def }
  /rows { cvi /Height exch def }
.dicttomark readonly def

% Recognize MIFF image classes.
/miffclasses mark
  /DirectClass {
    /DeviceRGB setcolorspace
    /BitsPerComponent depth def
    /Decode [ 0 1 0 1 0 1 ] def
  }
  /PseudoClass {
    [ /Indexed
                % The MIFF documentation lies about the size of pixels
                % for this case: the pixel size is determined only by
                % the number of colors, and is not affected by the image
                % depth.  Specifically, if there are 256 or fewer colors
                % but the depth (of color map entries) is 16, each pixel
                % is still only 1 byte, not 2.
      currentdict /colors known {
        /DeviceRGB colors 1 sub
        /BitsPerComponent colors 256 le { 8 } { 16 } ifelse def
        colors 3 mul string depth 8 eq {
          f exch readstring pop
        } {
                % 16-bit color map entries: take only the high-order byte.
          0 1 2 index length 1 sub {
            f read pop 2 index 3 1 roll put f read pop pop
          } for
        } ifelse
      } {
        /colors 256 def
        /DeviceGray 255
        256 string 0 1 255 { 1 index exch dup put } for
      } ifelse
    ] setcolorspace
    /Decode [ 0 1 BitsPerComponent bitshift 1 sub ] def
  }
.dicttomark readonly def

% Recognize MIFF compression methods.
/rlstring 768 string def
/rlread {
                % packets is not reliable -- disregard it.
  dup rlstring 0 3 getinterval readstring {
    pop read pop 3 mul 3 3 2 index {
      rlstring exch rlstring 0 3 getinterval putinterval
    } for
    rlstring 0 3 -1 roll 3 add getinterval
  } {
    pop pop ()
  } ifelse
} bind def
/miffcompress mark
  /Uncompressed { f }
  /RunLengthEncoded { { f rlread } }
  /Zip { [ f /FlateDecode filter cvlit /rlread cvx ] cvx }
.dicttomark readonly def

% Read a MIFF file and display the image.
/viewmiff {		% <filename> viewmiff -
  50 dict begin
  /fname 1 index def
  /f exch (r) file def
                % Set defaults.
  /ImageType 1 def
  /class /DirectClass def
  /compression /Uncompressed def
  /depth 8 def
  /packets 16#7fffffff def
                % Read and parse the header.
  { f token pop
    dup (:) eq { pop exit } if
    dup type /nametype eq {
      1024 string cvs (=) search {
        exch pop miffwords exch .knownget { exec } { pop } ifelse
      } {
        pop	% who knows?
      } ifelse
    } {
      pop	% probably a comment in braces
    } ifelse
  } loop
                % Read and display the image.
  miffclasses class get exec
  /DataSource miffcompress compression get exec def
  /FITPAGE where
  {
    /FITPAGE get
    {
      % we've already set the image color space, so
      % push it on the stack, and set it again after
      % setting the page size
      currentcolorspace
      <</PageSize [Width Height] >> setpagedevice
      setcolorspace
    } if
  } if

/ImageMatrix [Width 0 0 Height neg 0 Height] def
  currentpagedevice /PageSize get
    dup 0 get exch 1 get scale
  gsave 0.8 setgray 0 0 1 1 rectfill grestore	% provide background
  currentdict image
  showpage
                % Clean up.
  f closefile
  end
} bind def

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