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Celestine#

Celestine Logo

A neat library and DSL for creating graphics using SVG

Installation#

Add to shards.yml

dependencies:
  celestine:
    github: celestinecr/celestine

Usage#

Drawing#

First, all drawing is done through Celestine.draw this returns a string SVG element, or works on an IO. You can easily embed this into webpages for dynamic server side drawing of assets.

Celestine.draw takes a block which takes a Celestine::Svg (or ctx in the examples), the basis of all DSL calls in Celestine.

Celestine.draw do |ctx|
end

You can create objects to be drawn with one of two methods.

Celestine.draw do |ctx|
  # use this context's DSL methods
  ctx.rectangle do |r|
    r.x = 10
    r.y = 100
    r.fill = "black"
    r # You must return the drawable item at the end of the DSL method.
  end

  # Create the object and add it manually
  r = Celestine::Rectangle.new
  r.x = 10
  r.y = 100
  r.fill = "black"
  ctx << r
end

All context methods such as circle or rectangle take a block that takes their respective types, and needs to have an object of that type returned.

Currently Implemented#

A short list of the Celestine types that can be used by Celestine::Svg and their DSL methods

Nested SVG#

Celestine::Svg allows you to nest SVG.

Celestine.draw do |ctx|
  ctx.svg do |svg_doc2|
    svg_doc2.rectangle do |r|
      r
    end

    svg_doc2.circle do |c|
      c
    end

    svg_doc2
  end
end

Groups#

Celestine::Group allows you to group multiple elements under one parent. You can manipulate the x, y, and other attributes to apply them to the whole group, or just use it to combine elements easier.

Celestine.draw do |ctx|
  ctx.group do |g|
    g.rectangle do |r|
      r
    end

    g.circle do |c|
      c
    end

    g
  end
end

Groups cannot define objects like Celestine::Svg can. Groups also cannot use the mask, filter, or marker DSL methods as they define in the SVG document.

Use#

Celestine::Use can be used to save space in an SVG, and reuse certain elements without the need to copy the entire object into your SVG document.

The only caveat is that the use SVG element cannot change attributes it both doesn't own itself, or ones that have been set by it's ancestor, except in the case of x, y, width, and height. For example, the use element cannot change the radius of a circle even if the radius attribute had never been set.

Celestine::Use also requires that the drawable it is copying has an id set. If not Celestine::Use will still let you reference an ID that doesn't exist if you run use with a string id.

You can do this only with Celestine::Svg (or ctx in the examples). Celestine::Group, Celestine::Mask, Celestine::Marker cannot define drawables. The use element will only copy elements in the current SVG document you are in, so if you nest SVG inside SVG you need to be wary of how you define objects.

Celestine.draw do |ctx|
  # Only `Celestine::Svg` is allowed to "define" objects.
  ctx.rectangle(define: true) do |r|
    # Set r's x, y, width, height and other attributes here
    r.id = "our-rect" # YOU MUST SET AN ID TO BE ABLE TO REUSE A COMPONENT, OR THERE IS NO WAY TO REFERENCE IT.
    r
  end

  ctx.use do |use|
    use.x = 100
    use.y = 3000
    use.width = 99
    use.height = 99    
    use.fill = "black"

    # Cannot use this because `Celestine::Use` cannot change attributes specific to a drawable
    # only the attributes its shares with the type it's using.
    # use.radius_x = 1000

    use
  end
end

Transform#

Most drawables can use the transform method to translate, rotate, scale, and skew drawables.

Celestine.draw do |ctx|
  ctx.rectangle do |r|
    # Set r's x, y, width, height and other attributes here
    r.transform do |t|
      t.rotate(60, 0, 0) # Rotate by 60 degrees, at origin 0, 0
      t.translate(50, 60) # Move by 50, 60
      t.scale(100, 100) # Scale up 100x
      t.skew_x(10)
      t.skew_y(10)
      t.matrix(1.0, 1.0, 1.0, 1.0, 1.0, 1.0)
      t
    end
    r
  end
end

Masking#

You can use masks to make complicated shapes.

Celestine.draw do |ctx|
  our_mask = ctx.mask do |mask|
    mask.id = "our-mask" # YOU MUST SET A UNIQUE ID FOR THE MASK!
    mask.rectangle do |r| # Works just like a group
      # Set r's x, y, width, height and other attributes here
      r.fill = "black" # Will make everything under it invisibile and transparent
      r.fill = "white" # Will make everything under it visible
      r
    end
    mask
  end

  ctx.circle do |c|
    # Set c's x, y, radius and other attributes here
    c.set_mask our_mask # Set with the mask object directly
    c.set_mask "our-mask" # Set via string id
    c
  end
end

Patterns#

You can apply complciated tiling/repeating fills and strokes using the pattern DSL.

Celestine.draw do |ctx|
  our_pattern = ctx.pattern do |pattern|
    pattern.id = "our-pattern" # ALWAYS SET ID FOR A PATTERN OR IT CAN'T BE USED!
    pattern.rectangle do |r|
      r
    end
    pattern
  end

  ctx.circle do |c|
    # Either
    c.set_fill(our_pattern)
    # or
    c.set_stroke(our_pattern)
    c
  end
end

Gradients#

You can apply gradient fills and strokes using the linear_gradient and radial_gradient DSLs

Celestine.draw do |ctx|
  our_gradient = ctx.linear_gradient do |gradient|
    gradient.id = "our-gradient" # ALWAYS SET ID FOR A GRADIENT OR IT CAN'T BE USED!
    gradient.stop do |stop|
      stop.offset = 10
      stop.offset_units = "%"
      stop.color = "red"
      stop.opacity = 1.0
      stop
    end
    gradient
  end

  ctx.circle do |c|
    # Either
    c.set_fill(our_gradient)
    # or
    c.set_stroke(our_gradient)
    c
  end
end

Animate#

You can animate most simple SVG attributes using animate and the from and to attributes. 

Celestine.draw do |ctx|
  ctx.circle do |c|
    # IF ANIMATING AN ATTRIBUTE DO NOT SET IT IN ANY WAY, IT WILL OVERRIDE THE ANIMATION, BLAME SVG NOT ME
    # EX:
    #     Using `c.radius = 100` will ruin the animation.
    c.animate do |a|
      a.attribute = "r" # Choose it directly
      a.attribute = Celestine::Circle::Attrs::RADIUS # Choose it using the predefined constants
      a.from = 100
      a.to = 200
      a.duration = 10
      a.repeat_count = "indefinite"
      a
    end
    c
  end
end

You can also animate more complicated attributes and transition using the values array. SVG attempts to interpolate these values when possible.

If you use values and don't also use the key_times array to designate the timing changes, it will evenly space the animation values in the alotted time. 

Celestine.draw do |ctx|
  ctx.circle do |c|
    c.animate do |a|
      a.attribute = Celestine::Circle::Attrs::Fill
      a.values << "red" # Will start the color of the fill at red
      a.values << "blue" # Then interpolate to blue
      a.values << "red" # Then interpolate back to red.
      a.duration = 10
      a.repeat_count = "indefinite"
      a
    end

    c.animate do |a|
      a.attribute = Celestine::Circle::Attrs::Stroke
      a.values << "red" # Will start the color of the fill at red
      a.values << "blue" # Then interpolate to blue
      a.values << "red" # Then interpolate back to red.

      a.key_times << 0.0  # Change to red to start. You should almost always use 0.0 as your first key_times value
      a.key_times << 0.25 # Interpolate to blue at 25% of the duration
      a.key_times << 0.75 # Interpolate to red at 75% of the duration
      a_key_times << 1.0  # End the animation

      a.duration = 10
      a.repeat_count = "indefinite"
      a
    end
    c
  end
end

AnimateMotion#

You can animate movement along paths using animate_motion.

Celestine.draw do |ctx|
  ctx.circle do |c|
    c.animate_motion do |a|
      # Make the path the animateMotion element will follow.
      a.mpath do |path|
        path.a_move(200, 200)
        path.r_line(20, 20)
        path.r_line(-20, 20)
        path.r_line(-20, -20)
        path.r_line(20, -20)
        path
      end
      a.duration = 10
      a.repeat_count = "indefinite"
      a
    end
    c
  end
end

AnimateTransform#

You can animate transform elements using animate_transform_*.

Only rotate is supported right now. 

Celestine.draw do |ctx|
  ctx.circle do |c|
    c.animate_transform_rotate do |a|
      a.use_from = true # Need to set these to allow `from` to render in the SVG element
      a.use_to = true   # Need to set these to allow `to` to render in the SVG element
      a.from_angle = 0
      a.to_angle = 360
      a.from_origin_x = a.from_origin_y = a.to_origin_x = a.to_origin_y = 0
      a.duration = 10
      a.repeat_count = "indefinite"
      a
    end
    c
  end
end

Filters#

You can do some cool filtering using the filter DSL.

Celestine.draw do |ctx|
  our_filter = ctx.filter do |f|
    f.id = "our-filter" # ALWAYS SET ID FOR A FILTER OR IT CAN'T BE USED!
    f.blur do |b|
      b.standard_deviation = 5
      b
    end
    f
  end

  ctx.circle do |c|
    # Either
    c.set_filter("our-filter")
    # or
    c.set_filter(our_filter)
    c
  end
end

Currently Implemented#