Re: [NTG-context] How to "unfill" a picture?

24 Jun 2009

      Hi Nicola,

Thank you very much for your example and the idea. It's amazing,
I thought it's just a metafont thing and metapost just can't do that.

Thank you for your information again.

On Wed, Jun 24, 2009 at 10:12 PM, Nicola wrote:
...
In article
<769ba7780906240342s4939ac2foe7bfd783ad2e82ee@mail.gmail.com>,
 Zhichu Chen  wrote:
...
Well, my example is too simple. Actually, I was trying to draw a
treble clef
If your goal is to draw a path with pens of varying width (kind of
calligraphic strokes),'penpos' and 'penstroke' may be your friends
(defined in plain.mp). This is what I've come out with by about 15
minutes of trial and error (disclaimer: this is my first attempt at
using these macros beyond trying to draw a sans-serif 'l' - I'm not a
designer at all):
  fill unitsquare scaled 12cm shifted (-6cm,-6cm) withcolor .625red;
  b = 2pt; % Default pen width
  w = 30mm; % Width of treble clef
  h = 100mm; % Height of treble clef
  % Specify breadth and angle of pen at keypoints:
  penpos 1 (0.5b, 30);
  penpos 1.5 (b, 15);
  penpos 2 (3b, 0);
  penpos 3 (5b, -90);
  penpos 4 (3b, -180);
  penpos 5 (b, 90);
  penpos 6 (5b,0);
  penpos 6.5 (4b, -30);
  penpos 7 (.5b, 0);
  penpos 8 (5b, 90);
  penpos 9 (3b, -180);
  penpos 10 (b, -180);
  % Fix x coords of keypoints
  x1=0;
  x1.5=1/2[x1,x2];
  x5=x1=x3=x8;
  x10=1/2[x9,x1];
  x7=1/2[x3,x4];
  x4-x6=w;
  x1=1/2[x2,x4];
  x3-x2=x2-x6;
  x9=1/2[x1,x2];
  x6.5=1/2[x5,x6];
  % Fix y coords of keypoints
  y1=0;
  y1.5=y1;
  y6=y2=y4=1/2[y3,y1];
  y3-y1=y1-y5=1/10h;
  y5-y10=2(y3-y1);
  y8-y7=y3-y1;
  y9=y7;
  y8-y3=y3-y10;
  y6.5=1/2[y6,y7];
  drawoptions (withcolor background);
  % Draw (an incomplete and ugly) treble clef
  penstroke z1e .. z1.5e .. z2e .. z3e .. z4e .. z5e .. z6e .. z6.5e ..
z7e .. z8e .. z9e .. z10e;
  drawoptions(withcolor black);
  labels.lft(1,1.5,2,3,4,5,6,6.5,7,8,9,10);
You must take special care never to cross the left and right edges of
the pen. See The METAFONTbook for details and examples.
Regards,
Nicola
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Chen
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