Rasem
rasem is a pure ruby gem that allows you to describe your SVG images in ruby code.
Why Rasem
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Did you ever want to visualize some data in a nice image?
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Do you want to draw a complex image that is easier to describe using a code?
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Would you like to power your HTML 5 site with nicely drawn SVG images?
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Do you need to generate nice images from your ruby code?
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Are you fed up with using DIVs and Javascript to draw simple graphs?
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Is your server overwhelmed with sending PNG images that can be described in a few bytes using SVG?
Rasem allows you to generate SVG images that can be easily exported to other formats and embed in an HTML 5 page.
Features
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Draw basic elements: line, rectangle, rouned rectangle, circle, ellipse, polygon and polyline.
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Use SVG styles such as stroke-width, opacity and fill.
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Use SVG transformations such as translate, scale, rotate, skewX/Y and matrix
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Create SVG groups for better editing in SVG editors.
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Create SVG paths using ruby blocks
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Use definitions to create shapes and reuse them in your image
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Create SVG gradients
Coming features:
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Include all SVG standard elements such as filters
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Create default rake and thor tasks to convert your .rasem files to .svg.
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Embed other images in your SVG image
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Output to more formats such as PNG.
Rasem is still in alpha release. Please report your bugs so that we can work on it. You are welcome to contribute to the project by adding more features and fixing bugs. The end goal of the project is to fully support SVG standard and make it easy to use.
Installation
gem install rasem
Usage
There are two main methods to generate images with Rasem.
Command line
Create a file with extension .rasem. Here is a sample file test.rasem
self.width = 100
self.height = 100
circle 20, 20, 5
circle 50, 50, 5
line 20, 20, 50, 50
Save this file and execute the command
rasem test.rasem
A file test.svg will be generated.
Ruby code
You can generate the image from your ruby code. This has several uses such as sending the image on the fly from a Rails application.
Here is a simple example
require 'rasem'
img = Rasem::SVGImage.new(:width=>100, :height=>100) do
circle 20, 20, 5
circle 50, 50, 5
line 20, 20, 50, 50
end
puts img.output
img.output is the SVG code generated for this images.
More Examples
The following examples are for .rasem files. These are actually ruby scripts that are executed to generate the image. So, you can write arbitrary ruby code in .rasem files as you will see.
simple_graph.rasem
nodes = [[10,10], [20,20], [10,20]]
radius = 3
with_style :fill=>"white", :stroke=>"black" do
for node in nodes
circle node.first, node.last, radius
end
end
line nodes[0].first, nodes[0].last, nodes[1].first, nodes[1].last,
:stroke=>"blue"
Here is a more sophisticated example.
tictactoe.rasem
self.width = 150
self.height = 150
board = [['x', 'o', 'x'],
['o', '-', 'o'],
['x', 'o', 'x']]
def draw_x(x,y)
group :stroke=>"red" do
line x-20, y-20, x+20, y+20
line x-20, y+20, x+20, y-20
end
end
def draw_o(x,y)
circle x, y, 20, :stroke=>"blue", :fill=>"white"
end
group :stroke=>"black" do
rectangle 0, 0, 150, 150, :stroke_width=>2, :fill=>"white"
line 50, 0, 50, 150
line 100, 0, 100, 150
line 0, 50, 150, 50
line 0, 100, 150, 100
end
board.each_with_index do |row, row_index|
row.each_with_index do |cell, column_index|
if cell == "x"
draw_x row_index * 50 + 25, column_index * 50 + 25
elsif cell == "o"
draw_o row_index * 50 + 25, column_index * 50 + 25
end
end
end
Here are some examples that show how you can generate images from your ruby code.
You can generate SVG and store it to file
img = Rasem::SVGImage.new(:width => 100, :height => 100)
img.line(0, 0, 100, 100)
File.open("test.svg", w") do |f|
img.write(f)
end
You can use pass a block to SVGImage.new to make things more compact
img = Rasem::SVGImage.new(100, 100) do
line(0, 0, 100, 100)
end
# Image is closed automatically
# Write to file
You can make your code even more compact by passing the file as a last argument to SVGImage.new
File.open("test.svg", "w") do |f|
Rasem::SVGImage.new({:width => 100, :height => 100}, f) do
line(0, 0, 100, 100)
end
end
You can use transformations on created objects (translate, scale, rotate, skew, matrix)
img = Rasem::SVGImage.new(:width => 100, :height => 100) do
circle(0, 0, 10).translate(50, 50).scale(2, 1.5)
end
Here is an example showing how to generate a path using ruby code.
require 'rasem'
width = 100
height = 200
img = Rasem::SVGImage.new(:width => width, :height => height) do
path("stroke" => "black") do
moveToA(0, height / 2.0)
vlineTo(height / 2.0 - 50)
curveTo(50, 40, 0, 0, 50, 0)
curveTo(-30, -50, 0, 0, 10, -30)
vlineTo(-(height / 2.0 - 60))
end
end
File.open("path.svg", "w") do |f|
img.write(f)
end
Using definitions and reuse them later
img = Rasem::SVGImage.new(:width => 100, :height => 100) do
defs do
group(:id => "group1") do
circle(0, 0, 20)
text(0, 5, :fill => "red") { raw "hi!" }
end
end
use("group1", :x => 50, :y => 25)
use("group1", :x => 50, :y => 75, :fill => "blue")
end
Ruby method def_group to use definitions. It create a group inside ‘defs’ with the given id and populate it using the block. The second optional argument controls the behaviour if the id is already in use, you can :fail, :update the existing element (and return the new one), or :skip the new one (effectively skipping the block, and returning the existing element).
img = Rasem::SVGImage.new(:width => 100, :height => 100) do
g = def_group("group1") do
circle(0, 0, 20)
end
g = def_group("group1", :update) do
circle(0, 0, 20)
text(0, 5, :fill => "red") { raw "hi!" }
end
use(g, :x => 50, :y => 25)
use(g, :x => 50, :y => 75, :fill => "blue")
end
An example of gradients usage
img = Rasem::SVGImage.new(:width => 100, :height => 100) do
r1 = radialGradient("rgrad1") do
stop("0%", "green", 1)
stop("100%", "blue", 1)
end
r2 = radialGradient("rgrad2") do
stop("0%", "yellow", 1)
stop("100%", "red", 1)
end
r2 = radialGradient("rgrad2", {}, :skip) do
stop("0%", "blue", 1)
stop("100%", "red", 1)
end
circle(50, 25, 20, :fill => r1.fill)
circle(50, 75, 20, :fill => r2.fill)
end
Contributing to rasem
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Check out the latest master to make sure the feature hasn’t been implemented or the bug hasn’t been fixed yet
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Check out the issue tracker to make sure someone already hasn’t requested it and/or contributed it
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Fork the project
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Start a feature/bugfix branch
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Commit and push until you are happy with your contribution
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Make sure to add tests for it. This is important so I don’t break it in a future version unintentionally.
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Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.
Copyright
Copyright © 2011 Ahmed Eldawy. See LICENSE.txt for further details.