Class: Fleximage::Operator::ImageOverlay

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

Overview

Adds an overlay to the base image. It’s useful for things like attaching a logo, watermark, or even a border to the image. It will work best with a 24-bit PNG with alpha channel since it will properly deal with partial transparency.

image.resize(image_overlay_path, options = {})

image_overlay_path is the path, relative to RAILS_ROOT where the image you want superimposed can be found.

Use the following keys in the options hash:

  • size: The size of the overlayed image, as '123x456' or [123, 456].

    By default the overlay is not resized before compositing. Use this options if you want to resize the overlay, perhaps to have a small logo on thumbnails and a big logo on full size images. Other than just numerical dimensions, the size parameter takes 2 special values :scale_to_fit and :stretch_to_fit. :scale_to_fit will make the overlay fit as much as it can inside the image without changing the aspect ratio. :stretch_to_fit will make the overlay the exact same size as the image but with a distorted aspect ratio to make it fit. :stretch_to_fit is designed to add border to images.

  • alignment: A symbol that tells Fleximage where to put the overlay. 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 overlay from it’s :alignment anchor, in '123x456' or [123, 456] format. Useful to give a bit a space between your logo and the edge of the image, for instance. NOTE: Due to some unexpected (buggy?) RMagick behaviour :offset will work strangely if :alignment is set to a 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 overlay gets composited onto the image. 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.

Example:

@photo.operate do |image|
  image.image_overlay('images/my_logo_with_alpha.png',
    :size => '25x25',
    :alignment => :top_right,
    :blending => :screen
  )
end

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(image_overlay_path, options = {}) ⇒ Object 



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# File 'lib/fleximage/operator/image_overlay.rb', line 52

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

  #load overlay
  overlay = Magick::Image.read(image_overlay_path).first

  #resize overlay
  if options[:size]
    if options[:size] == :scale_to_fit || options[:size] == :stretch_to_fit
      x, y = @image.columns, @image.rows
    else
      x, y = size_to_xy(options[:size])
    end
  
    method = options[:size] == :stretch_to_fit ? :stretch : :scale
    send(method, [x, y], overlay)
  end

  #prepare arguments for composite!
  args = []
  args << overlay                                               #overlay image
  args << symbol_to_gravity(options[:alignment] || :center)     #gravity
  args += size_to_xy(options[:offset]) if options[:offset]      #offset
  args << symbol_to_blending_mode(options[:blending] || :over)  #compositing mode
  
  #composite
  @image.composite!(*args)

  return @image
end