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 



52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
 
# 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