[QUIZ] Circle Drawing (#166)

M

Matthew Moss

[Note: parts of this message were removed to make it a legal post.]

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## Circle Drawing (#166)

This week we're going to keep it simple... very simple.

Given a radius, draw an ASCII circle.

For example:

ruby circle.rb 7

Should produce a circle of radius 7:

#####
## ##
# #
# #
# #
# #
# #
# #
# #
# #
# #
# #
# #
## ##
#####


Note that most fonts do not have a square aspect ratio, which is why the
above output may look like an oval, despite my calculations for a circle. It
is acceptable if your code produces similar output.


However, _for extra credit_ you may support an additional argument that
specifies the aspect ratio (height divided by width).

ruby circle.rb 7 1.4

This should draw a circle of radius 7 with aspect ratio of 1.4. If done
correctly, your output will actually look like a circle (assuming 1.4 is an
accurate measure of the actual aspect ratio).
 
C

Clifford Heath

Matthew said:
However, _for extra credit_ ...

What about bonus points for using only *integer* arithmetic and no transcendentals?
I wrote C code for that which is hiding somewhere :)
 
T

ThoML

Hi,
For example:

ruby circle.rb 7

Should produce a circle of radius 7

I'm not sure if this is intentional but the circle is 15 characters
high. Of course, the line has to be counted in too.
Nevertheless ... :)

Regards,
Thomas.
 
R

Robert Dober

Hi,


I'm not sure if this is intentional but the circle is 15 characters
high. Of course, the line has to be counted in too.
Nevertheless ... :)

Regards,
Thomas.
2*7 = 15, simple LOL.

I finally decided against it because of simplicity, but I believe that
it is more beautyful to add a "middle" line, especially for small r's.

Robert
 
E

Eric Mahurin

[Note: parts of this message were removed to make it a legal post.]

Hi,




I'm not sure if this is intentional but the circle is 15 characters
high. Of course, the line has to be counted in too.
Nevertheless ... :)

Regards,
Thomas.
Depends on where you are measuring the radius:

outside: 7.5
inside: 6.5 (white space is 13 characters high)
center: 7 (center of bottom to center of top is 14)
 
M

Matthew Moss

For example:
Depends on where you are measuring the radius:

outside: 7.5
inside: 6.5 (white space is 13 characters high)
center: 7 (center of bottom to center of top is 14)

It was quite intentional that my circle of radius 7 took up 15 rows of
characters. This is a common issue when dealing with computer
graphics: how do you measure distance on a field of discrete elements?

In computer graphics, this is often not a big deal when drawing 3d
objects, especially if you have blurring, other post-processing, or
anti-aliasing going on. It is much more important when you are trying
to render a HUD or UI elements, for example, that you want pixel-
perfect to the artwork provided. Many graphics cards have a setting
you can enable/disable to offset coordinates by half a pixel...
Putting it into the correct mode and setting your texturing unit to
point sampling mode (as opposed to tri-/bi-linear sampling) will give
you pixel-perfect results.

So, in the case as I presented it, I was measuring from the center of
the character cell, which is 15 rows high *if measured from the top
edge of the top row to the bottom edge of the bottom row*. But as Eric
pointed out, it's only 14 if you measure from character cell center's.
 
A

Andrea Fazzi

Matthew Moss ha scritto:
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

The three rules of Ruby Quiz 2:

1. Please do not post any solutions or spoiler discussion for this
quiz until 48 hours have passed from the time on this message.

2. Support Ruby Quiz 2 by submitting ideas as often as you can! (A
permanent, new website is in the works for Ruby Quiz 2. Until then,
please visit the temporary website at

<http://splatbang.com/rubyquiz/>.
3. Enjoy!

Suggestion: A [QUIZ] in the subject of emails about the problem
helps everyone on Ruby Talk follow the discussion. Please reply to
the original quiz message, if you can.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

## Circle Drawing (#166)

This week we're going to keep it simple... very simple.

Given a radius, draw an ASCII circle.

For example:

ruby circle.rb 7

Should produce a circle of radius 7:

#####
## ##
# #
# #
# #
# #
# #
# #
# #
# #
# #
# #
# #
## ##
#####


Note that most fonts do not have a square aspect ratio, which is why the
above output may look like an oval, despite my calculations for a circle. It
is acceptable if your code produces similar output.


However, _for extra credit_ you may support an additional argument that
specifies the aspect ratio (height divided by width).

ruby circle.rb 7 1.4

This should draw a circle of radius 7 with aspect ratio of 1.4. If done
correctly, your output will actually look like a circle (assuming 1.4 is an
accurate measure of the actual aspect ratio).
Here my solution. It is available on pastie:

http://pastie.org/215379
http://pastie.org/215380 (specs)

and it is also attached below:

#
# Solution to Ruby Quiz #166 - Circle Drawing
#
# Usage:
#
# Circle.new(5).to_s
#
# or:
#
# Circle.new(5, 2).to_s
#
#
# or:
#
# Circle.new(5, 2, 'x').to_s
#

# Objects of class Circle draw circles on stdout. The aspect ratio
# correction is actually made drawing an ellipse with semimajor axis
# (a) equals to the given circle radius and semiminor axis (b) equals
# to a / aspect_ratio.
#
# Circle class is responsible to
#
# * initialize a Circle object with the given radius, aspect ratio
# and drawing char
#
# * initialize a canvas
#
# * draw the circle on its internal canvas
#
# * convert the canvas to string for output on stdout
#
class Circle

# cx, cy are the coordinates of the circle's center.
attr_reader :cx, :cy

attr_reader :radius

# w, h are width and height of the canvas
attr_reader :w, :h

# canvas is a linear array that is initially filled with spaces
attr_reader :canvas

#
# Initialize a Circle object passing a value for radius, aspect
# ratio and drawing character.
#
def initialize(radius, aspect_ratio = 1.0, char = '#')

@radius = radius.to_i
@aspect_ratio = aspect_ratio.to_f
@char = char

fail "Error: radius must be > 0" if @radius <= 0
fail "Error: aspect ratio must be > 0" if @aspect_ratio <= 0

# a is the semimajor axis of the ellipse and is equal to the given
# radius
@a = @radius

# b is the semiminor axis of the ellipse and is calculated from a
# and the given aspect ratio
@b = (@a / @aspect_ratio).ceil

# calculate the size of the canvas
@w, @h = (@a + 1) * 2, (@b + 1) * 2

# center coordinates correspond to the size of semiaxis.
@cx, @cy = @a, @b

# initialize the canvas with spaces
@canvas = Array.new(@w * @h, ' ')

# draw ellipse on canvas
draw_ellipse(@a, @b)
end

#
# Print circle on stdout.
#
def to_s
result = ""
(0..@h - 1).each do |line|
result << @canvas[line * @w..line * @w + @w - 1].to_s << "\n"
end
result
end

private

#
# Draw the given character on canvas to the given coordinates.
#
def point(x, y)
@canvas[y * @w + x] = @char
end

#
# Translates and mirrors point (x, y) in the quadrants taking
# advantage of the simmetries in the ellipse. Thus, for a given
# point (x, y) the method plot three other points in the remaining
# quadrants.
#
def plot_four_points(x, y)
point(@cx + x, @cy + y)
point(@cx - x, @cy + y)
point(@cx + x, @cy - y)
point(@cx - x, @cy - y)
end

#
# Draw an ellipse on canvas. This method implements a Bresenham
# based algorithm by John Kennedy
# (http://homepage.smc.edu/kennedy_john/BELIPSE.PDF)
#
# The method calculates two set of points in the first quadrant. The
# first set starts on the positive x axis and wraps in a
# counterclockwise direction until the tangent line slope is equal
# to -1. The second set starts on the positive y axis and wraps in
# a clockwise direction until the tangent line slope is equal to -1.
#
def draw_ellipse(a, b)
a_square = 2 * a**2
b_square = 2 * b**2

draw_first_set(a, b, a_square, b_square)
draw_second_set(a, b, a_square, b_square)
end

#
# The method increments y and decides when to decrement x testing
# the sign of a function. In this case, the decision function is
# (2*ellipse_error+x_change) and its value is calculated
# iteratively.
#
def draw_first_set(a, b, a_square, b_square)

x, y = a, 0
x_change, y_change = b**2 * (1 - 2 * a), a**2
stopping_x, stopping_y = b_square * a, 0
ellipse_error = 0

while(stopping_x >= stopping_y) do
plot_four_points(x, y)
y += 1
stopping_y += a_square
ellipse_error += y_change
y_change += a_square
if (2 * ellipse_error + x_change) > 0
x -= 1
stopping_x -= b_square
ellipse_error += x_change
x_change += b_square
end
end

end

#
# The method increments x and decides when to decrement y testing
# the sign of a function. In this case, the decision function is
# (2*ellipse_error+y_change) and its value is calculated
# iteratively.
#
def draw_second_set(a, b, a_square, b_square)

x, y = 0, b
x_change, y_change = b**2, a**2 * (1 - 2 * b)
stopping_x, stopping_y = 0, a_square * b
ellipse_error = 0

while stopping_x <= stopping_y do
plot_four_points(x, y)
x += 1
stopping_x += b_square
ellipse_error += x_change
x_change += b_square
if (2 * ellipse_error + y_change) > 0
y -= 1
stopping_y -= a_square
ellipse_error += y_change
y_change += a_square
end
end

end

end

# Usage:
#
# ruby circle.rb 7 #=> print out a circle of radius 7
#
# ruby circle.rb 7 1.8 #=> print out a circle of radius 7 and aspect
ratio 1.8
#
# ruby circle.rb 7 1.8 x #=> print out a circle of radius 7 and aspect
ratio 1.8
# using the ascii char 'x'
#

print Circle.new(ARGV[0], ARGV[1] || 1.0, ARGV[2] || '#').to_s if $0 ==
__FILE__
 
M

Martin Boese

Here's my solution, it creates a buffer to draw into, once done it puts it on
the screen:

----- circle.rb -----
class Circle
def initialize(rad, asp)
@rad, @asp = rad, asp # radius, horizontal aspect ratio
@height = rad*2+1 # hight/width of the pictures
@width = (@height*asp).round
@buf = Array.new(@height, ' ').map { |e| Array.new(@width, ' ') }
end
def draw
(0..Math::pI*2).step(1/(@rad*@asp*2)) do |deg|
@buf[((@height/2) + (Math::sin(deg)*@rad)).round] \
[((@width/2) + (Math::cos(deg)*@rad*@asp)).round] = '#'
end
@buf.map { |l| l.join + "\n"}.join
end
end
puts Circle.new((ARGV[0] || 7).to_i, (ARGV[1] || 1).to_f).draw
----- end circle.rb -----
 
T

ThoML

My solution makes circles with r=7 14 characters wide. This may be
incorrect. It's rather simple though.

Regards,
Thomas.


def draw_circle(r, ratio=1.0)
lines = []
a = 0.0
t2 = ratio / 2.0
(t2 - 0.1).step(r, ratio) do |h|
b = Math.sqrt(2.0 * h * r - h ** 2).round
u = r - b
v = [1.0, b - a].max
w = (r - u - v) * 2.0
lines << [(m = ' ' * u), (l = '#' * v), ' ' * w, l, m].join
a = b
end
out = lines.join("\n")
puts out
puts out.reverse
end

if __FILE__ == $0
draw_circle(*ARGV.map {|e| e.to_f})
end
 
B

Bill Kelly

My solution follows....

Regards,

Bill


# Ruby Quiz #166
#
# This draws a circle of the specified radius, modified
# by an optional aspect ratio and thickness factor.
#
# implementation notes:
# - for the fun of it, i forbade use of sqrt() and trancendentals
# - the circle is not drawn into a buffer before being printed
# - some values are empirically derived (thickness factor, in parciular)
#
# bugs:
# - the thickness factor causes bloat in small circles

ARGV.length >= 1 or abort("usage: #$0 radius [aspect] [thickness]")

radius = ARGV.shift.to_f
radius > 0 or abort("please provide radius of circle")

aspect = ARGV.shift.to_f
aspect > 0 or aspect = 1.0

thick = ARGV.shift.to_f
thick > 0 or thick = 1.0

hradius = (radius * aspect).ceil + (thick/2.0).round
vradius = radius.ceil + (thick/2.0).round

def get_radius_ch(rsq, dsq, tfactor)
(rsq - dsq).abs <= tfactor ? "*" : " "
end

tfactor = (thick * 4.0) + 2.5
rsq = radius**2
(-vradius).upto(vradius) do |y|
(-hradius).upto(hradius) do |x|
print(get_radius_ch(rsq, (x * (1.0/aspect))**2 + y**2, tfactor))
end
puts
end


# example: radius 7.0, aspect 1.0, thickness 1.0
#
# $ ruby 166_circle.rb 7 1 1
#
# *****
# ** **
# * *
# * *
# * *
# * *
# * *
# * *
# * *
# * *
# * *
# * *
# * *
# ** **
# *****
#
#
# example: radius 10.0, aspect 2.0, thickness 5.0
#
# $ ruby 166_circle.rb 10 2 5
#
#
# *****
# *******************
# *************************
# ******** ********
# ******* *******
# ****** ******
# ***** *****
# ***** *****
# ***** *****
# **** ****
# ***** *****
# ***** *****
# ***** *****
# **** ****
# ***** *****
# ***** *****
# ***** *****
# ****** ******
# ******* *******
# ******** ********
# *************************
# *******************
# *****
#
 
J

Juan Matías

# circle.rb

def draw(mtrx)
mtrx.each do |file|
puts file.to_s
end
nil
end

def new_mtrx(rdx,ratio)
size =3D rdx * (ratio.ceil) * 2
mtrx =3D Array.new(size).map!{ Array.new(size) }
(0..size-1).each do |file|
(0..size-1).each do |col|
mtrx[file][col] =3D " "
end
end
mtrx
end


def load_mtrx(mtrx,rdx,ratio=3D1)
(1..360).each do |grado|
x =3D ((Math.sin grado) * (rdx * ratio)) + (rdx * ratio)
y =3D ((Math.cos grado) * rdx) + rdx
mtrx[x.to_i][y.to_i] =3D "#"
end
nil
end

def main
rdx =3D ARGV[0].to_i
ratio =3D ARGV[1].to_f
mtrx =3D new_mtrx(rdx,ratio)
load_mtrx(mtrx,rdx,ratio)
draw(mtrx)
end

main

# end file

--=20
=ABQuien nunca ha cometido un error nunca ha probado algo nuevo.=BB
 
A

Aaron Baldwin

Here is my solution.

Aaron


class Circle
attr_accessor :radius, :aspect_ratio

def initialize(radius, aspect_ratio)
self.radius = radius
self.aspect_ratio = aspect_ratio == 0 ? 1 : aspect_ratio
end

def to_s
(0..y_diameter).inject('') do |rows, y|
rows + (0..x_diameter).inject('') do |row, x|
row + (on_circle?(x, y) ? '#' : ' ')
end + "\n"
end
end

private

def y_diameter
radius * 2
end

def x_diameter
y_diameter * aspect_ratio
end

def on_circle?(x,y)
Math.sqrt((x/aspect_ratio-radius)**2 + (y-radius)**2).round ==
radius
end
end

print Circle.new(ARGV[0].to_i, ARGV[1].to_f).to_s
 
J

Jon Garvin

Here's mine before I delved into trying to add the aspect ratio feature.


class Circle
def initialize(radius)
@radius = radius.to_i
end

def draw
(0..@radius*2).each do |x|
(0..@radius*2).each do |y|
print distance_from_center(x,y).round == @radius ? '#' : '.'
end
puts
end
end

def distance_from_center(x,y)
a = calc_side(x)
b = calc_side(y)
return Math.sqrt(a**2 + b**2)
end

def calc_side(z)
z < @radius ? (@radius - z) : (z - @radius)
end
end

Circle.new(ARGV.shift).draw
 
S

Sandro Paganotti

[Note: parts of this message were removed to make it a legal post.]

Here's mine

# initial values
r = ARGV[0].to_i; k = 360.0/(Math::pI*2)

# if r < 1 write error and exit
puts "USAGE: circle.rb radius [with radius >= 1]"; exit if r < 1

# get some points and map them on a matrix
m = Array.new(r).collect{|e|Array.new(r).fill(" ")}
j = [0.0,90.0,*(1...p=((vr=(r-1))*2)).to_a.collect{|e|
e*(90.0/p.to_f) }].each{|a|
vl=[Math.sin(a/k),Math.cos(a/k)].collect{|c| (c*vr).round }
m[vl[0]][vl[1]]="#" }
s = m.collect{|a| w=a.join(""); w.reverse+w }.join("\n")

# print the result
puts s.reverse+"\n"+s
 
L

Lars Christensen

Don't reinvent the wheel (no pun intended :)

require 'cairo'
radius = ARGV[0].to_f
aspect = (ARGV[1]||1.0).to_f
linewidth = (ARGV[2]||1.0).to_f
width = (aspect * radius * 2 + 1 + linewidth + 0.5).to_i
height = (radius * 2 + 1 + linewidth + 0.5).to_i
Cairo::ImageSurface.new(width, height) do |surface|
cr = Cairo::Context.new(surface)
cr.set_antialias(Cairo::ANTIALIAS_NONE)
cr.set_source_rgb(0,0,0)
cr.paint
cr.save
cr.scale(aspect, 1.0)
cr.arc(width / 2.0 / aspect + 0.5, height / 2.0 + 0.5, radius, 0, 2
* Math::pI)
cr.restore
cr.set_source_rgb(1,1,1)
cr.set_line_width(linewidth)
cr.stroke
height.times { |row|
puts cr.target.data[row * width * 4, width * 4].unpack("N*").map
{ |x| (x >> 8) > 0 ? '#' : ' ' }.join
}
end
 
A

Andrea Fazzi

Matthew Moss ha scritto:
## Circle Drawing (#166)

This week we're going to keep it simple... very simple.

Given a radius, draw an ASCII circle.

For example:

ruby circle.rb 7

Should produce a circle of radius 7:

#####
## ##
# #
# #
# #
# #
# #
# #
# #
# #
# #
# #
# #
## ##
#####


Note that most fonts do not have a square aspect ratio, which is why the
above output may look like an oval, despite my calculations for a circle. It
is acceptable if your code produces similar output.


However, _for extra credit_ you may support an additional argument that
specifies the aspect ratio (height divided by width).

ruby circle.rb 7 1.4

This should draw a circle of radius 7 with aspect ratio of 1.4. If done
correctly, your output will actually look like a circle (assuming 1.4 is an
accurate measure of the actual aspect ratio).

A bit of ruby art :)

http://pastie.org/216459
http://pastie.org/216462

I don't know if my benchmark is done properly.. I do it quickly and just
for fun :) Please give me feedback..

Benchmark details:

num_of_runs = 100
radius = 7
ratio = 2.0

This benchmark has been executed on a MacBook 2,16Ghz with 2Gb of RAM
running Linux Ubuntu 7.10.

Andrea
 
R

ruby

Just make test pass.... nothing clever!

Jean Lazarou


---- code -----------------

def symbolify value

res = value.to_s

def res.delete other_str
""
end

res

end

1000.times do |i|
s = symbolify(i)
raise "Not a string!" unless s.is_a? String
raise "Invalid chars!" unless s.delete("?*()-").empty?

x = eval(s)
raise "Decode failed!" unless i == x
end
 

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