%!PS

% Seed RNG, change the value to get different mountain
% shapes
1234 srand

% Rounded line joints
1 setlinejoin

% Scale coordinate system so 1 unit is 36 "points" (half an inch)
36 36 scale

% The image in drawn in a 10x10 unit square, with bottom left
% corner at (1, 1)

% Function drawblock
% Stack setup: red, green, blue, height, linewidth
% Draws a coloured block at the bottom of the image, with width equal
% to the entire image, with the specified height.  Gets a black outline
% of specified width, and is filled with specified RGB colour.
/drawblock {
	% Line settings
	setlinewidth
	0 setgray
	% Draw path
	newpath
	1 add	% (1,1) coordinate offset
	1 exch moveto
	10 0 rlineto
	11 1 lineto
	1 1 lineto
	closepath
	% outline and fill
	gsave
	stroke
	grestore
	setrgbcolor
	fill
} def

% Function mountain
% Stack setup: red, green, blue, height, linewidth
% Draws a mountain which slopes downward from left to right.
% Mountain begins at specified height.
% With each 1 unit movement to the right, the mountain height randomly
% changes.  Large downward steps have probability 0.6, small upward steps
% and flat sections each have probability 0.2.
% There is no code to handle the mountain hitting the bottom of the image
% frame before it hits the right hand boundary, so don't set the initial
% height too low or the image will break with non-negligible probability.
% Gets a black outline of specified width, and is filled with specified
% RGB colour.
/mountain {
	% Line settings
	setlinewidth
	0 setgray
	% Drawn path
	newpath
	1 add	% (1,1) coordinate offset
	1 exch moveto
	% 10 step loop
	10 {
		% Get a random number, reduce it mod 5
		rand 5 mod
		dup % Prepare for second comparison
		3 lt {
			% If 0 <=r <= 2
			1 -0.75 rlineto % Slope down
			pop		% No second comparison
		} {
			3 eq {
				% If r == 3
				1 0 rlineto	% No slope
		      	} {
				1 0.5 rlineto	% Slope up
		      	} ifelse
		} ifelse
	} repeat
	11 1 lineto
	1 1 lineto
	closepath
	% outline and fill
	gsave
	stroke
	grestore
	setrgbcolor
	fill
} def

% The actual image!
% sky
0.721 0.964 0.980 10 0.1 drawblock
% distant mountain
0.627 0.823 0.556 8 0.1 mountain
% midground mountain
0.741 0.513 0.078 7 0.15 mountain
% lake
0.290 0.258 0.560 4 0.15 drawblock
% foreground mountain
0.266 0.462 0.196 6 0.2 mountain
% orange sun
9 9 1 0 360 arc
1 0.5 0 setrgbcolor
fill

% Draw a thick frame around the whole image
0.25 setlinewidth
0 setgray
newpath
1 1 moveto
10 0 rlineto
0 10 rlineto
-10 0 rlineto
closepath
stroke

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