Class: Fleximage::Operator::Background

Inherits:
Base
  • Object
show all
Defined in:
lib/fleximage/operator/background.rb

Overview

Composites a transparent image over a colored backgroud

It accepts the following options:

  • color: the color of the background image. Use an RMagick named color or use the color method in Fleximage::Controller, or a Magick::Pixel object.

  • size: The size of the background image, in Fleximage size format.

    By default the background image is the same size as the foreground image

  • alignment: A symbol that tells Fleximage where to put the foreground image on top of the background image. Can be any of the following: :center, :top, :top_right, :right, :bottom_right, :bottom, :bottom_left, :left, :top_left. Default is :center

  • offset: the number of pixels to offset the foreground image from it’s :alignment anchor, in FlexImage size format. Useful to give a bit a space between your image and the edge of the background, for instance. NOTE: Due to some unexpected (buggy?) RMagick behaviour :offset will work strangely if :alignment is set to a corner non-corner value, such as :top or :center. Using :offset in these cases will force the overlay into a corner anyway.

  • blending: The blending mode governs how the foreground image gets composited onto the background. You can get some funky effects with modes like :copy_cyan or :screen. For a full list of blending modes checkout the RMagick documentation (www.simplesystems.org/RMagick/doc/constants.html#CompositeOperator). To use a blend mode remove the CompositeOp form the name and “unserscorize” the rest. For instance, MultiplyCompositeOp becomes :multiply, and CopyBlackCompositeOp becomes :copy_black.

Instance Method Summary collapse

Methods inherited from Base

#color, color, #execute, #initialize, #scale, #scale_and_crop, size_to_xy, #size_to_xy, #stretch, #symbol_to_blending_mode, #symbol_to_gravity

Constructor Details

This class inherits a constructor from Fleximage::Operator::Base

Instance Method Details

#operate(options = {}) ⇒ Object 



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# File 'lib/fleximage/operator/background.rb', line 33

def operate(options = {})
  options = options.symbolize_keys

  #default to a white background if the color option is not set
  color = options[:color] || 'white'

  #use the existing image's size if the size option is not set
  width, height = options.key?(:size) ? size_to_xy(options[:size]) : [@image.columns, @image.rows]

  #create the background image onto which we will composite the foreground image
  bg = Magick::Image.new(width, height) do 
    self.background_color = color
    self.format = 'PNG'
  end

  #prepare attributes for composite operation
  args = []
  args << @image
  args << symbol_to_gravity(options[:alignment] || :center)
  args += size_to_xy(options[:offset]) if options[:offset]
  args << symbol_to_blending_mode(options[:blending] || :over)

  #composite the foreground image onto the background
  bg.composite!(*args)

  return bg
end