%!
% readpnm library by Denis Moskowitz.  All Rights Reversed - share and enjoy.
/drawpnmdict 20 dict def
/drawpnm_width { /width drawpnm } def
    % draw a 1-unit wide pnm, unclipped, given a filename
/drawpnm_height { /height drawpnm } def
    % draw a 1-unit high pnm, unclipped, given a filename
/drawpnm_square { /square drawpnm } def
    % draw a pnm in the unit square, clipping as needed, given a filename
/drawpnm {
    % draw a ppm or pgm onto the page
    % modes are square, width, or height
    % pbm format differs from PS 1-bit format and cannot be easily supported
    drawpnmdict begin
	/mode exch def
	/filename exch def
	
	% open file handle
	/picfile filename (r) file def

	% read image file preamble (such as "P6 100 100 255")
	
	% read P (ascii 80)
	picfile read not {filename print (: read failure) print quit} if
	80 ne {filename print (: bad format) print quit} if
	% read magic number
	picfile read not {filename print (: read failure) print quit} if
	48 sub % convert to number

	% deal with magic number
	% only handle binary ppm  & pgm for now
	/channels 0 def
	dup 5 eq {/channels 1 def} if  %P5 = binary pgm grayscale
	dup 6 eq {/channels 3 def} if  %P6 = binary ppm rgb
	pop

	% die if format unsupported
	channels 0 eq {
	    filename print (: unsupported magic number) print quit
	} if 

	% get width, height, range as ps tokens
	/get_token { 
	    picfile token not {filename print (: read failure) print quit} if
	} def
	get_token /width exch def
	get_token /height exch def
	get_token /range exch def

	% after reading these tokens the file pointer should be at 
	% the beginning of the image data

	% calculate decode value
	% this scales the image values to the 0-255 range
	/bits 8 def
	/decode_max 2 bits exp 1 sub range div def
	
	% draw image
	gsave  % we'll be translating and changing the color space
	    mode /square eq {

		% determine offset for clipping purposes
		/side width height gt { height } { width } ifelse def
		newpath
		0 0 moveto 0 1 lineto 1 1 lineto 1 0 lineto closepath clip
		newpath

		% show center of image
		width side sub 2 div side div neg
		height side sub 2 div side div 
		translate
	    } if
	    mode /width eq {
		% use width as side, align with y=0
		/side width def
		0 height side div 1 sub translate
	    } if
	    mode /height eq {
		/side height def
	    } if

	    % select correct color space
	    channels 3 eq { 
		/DeviceRGB setcolorspace 
		/Decode [0 decode_max 0 decode_max 0 decode_max] def
	    } if
	    channels 1 eq {
		/DeviceGray setcolorspace 
		/Decode [0 decode_max] def
	    } if

	    % image dictionary argument for image operator
	    <<
		/ImageType 1
		/Width width
		/Height height
		/BitsPerComponent 8
		/Decode Decode
		/ImageMatrix [side 0 0 side neg 0 side]
		/DataSource picfile
	    >>
	    image
	grestore

	% close file
	picfile closefile
    end
} def