Class: RMagickTransformationScript

Inherits:
Object
  • Object
show all
Defined in:
lib/asset_compiler/rmagick_transformation_script.rb

Overview

Holds a reference to an instance of Magick::Image and manages operations on it. Used to provide a more consistent, higher-level api than is given by RMagick.

ImageTransformationScript automatically invokes Ruby’s garbage collector by calling GC.start upon instantiating a Magick::Image object. To bypass this, set the GC environment variable to ‘no’.

Constant Summary collapse

GRAVITY_TYPES = 
{
  :none      => Magick::ForgetGravity,
  :northwest => Magick::NorthWestGravity,
  :north     => Magick::NorthGravity,
  :northeast => Magick::NorthEastGravity,
  :west      => Magick::WestGravity,
  :center    => Magick::CenterGravity,
  :east      => Magick::EastGravity,
  :southwest => Magick::SouthWestGravity,
  :south     => Magick::SouthGravity,
  :southeast => Magick::SouthEastGravity
}

Instance Method Summary collapse

Constructor Details

#initialize(img, &block) ⇒ RMagickTransformationScript

Initialize an ImageTransformationScript where img is either a path to an image or an instance of Magick::Image.

Raises:

  • (ArgumentError) 


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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 25

def initialize img, &block
  @image = img      if img.is_a? Magick::Image
  @image = read img if img.is_a? String
  raise ArgumentError.new( 'img must be either a path to an image or a Magick::Image object' ) \
      unless @image
  
  instance_eval &block
  
  GC.start unless ENV['GC'] == 'no'
end

Instance Method Details

#crop_to(size_string, gravity = :center) ⇒ Object

Resizes the image proportionally to fit the smaller dimension, then crops excess. Optionally, a gravity setting may be provided. From the RMagick docs:

Gravity provides a convenient way to locate objects irrespective of the size of the
bounding region, in other words, you don't need to provide absolute coordinates in
order to position an object.

The default gravity setting is :center. Available settings are:

:none

don’t use gravity

:northwest

crop to northwest

:north

crop to north - good for vertical images

:northeast

crop to northeast

:west

crop to west

:center

crop to center - default

:east

crop to east

:southwest

crop to southwest

:south

crop to south

:southeast

crop to southeast

Usage:

img.crop_to '64x64'         # crops to center, 64x64 pixels
img.crop_to '64x64', :north # crops to north - common for thumbnailing portraits



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 127

def crop_to size_string, gravity = :center
  width, height = size_string.scan( /\d+/ ).collect { |i| i.to_i }
  max = ( width > height ? width : height )
  aspect = @image.columns.to_f / @image.rows.to_f
  @image.resize!( max, ( max / aspect ).to_i ) if     aspect < 1.0
  @image.resize!( (max*aspect).to_i, max )     unless aspect < 1.0
  #            radius, sigma,  blend, threshold
  unsharp_mask 0.5,    1.0,    0.5,   0.25
  @image.crop!( GRAVITY_TYPES[gravity], width, height )
  @image
end

#darken(factor = 0.25) ⇒ Object

Darkens the image. Defaults to a blend factor of 25%.

img.darken      # darkens the image 25%.
img.darken 0.40 # darkens the image 40%.



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 80

def darken factor = 0.25
  tint factor, factor, factor, '#000000'
end

#greyscale(overlay = '#aa9955') ⇒ Object

Converts the image to greyscale.

img.greyscale           # uses default overlay of #aa9955.
img.greyscale '#aaaaaa' # uses specified overlay.



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 87

def greyscale overlay = '#aa9955'
  @image = @image.quantize 256, Magick::GRAYColorspace
  tint 0.25, 0.25, 0.25, overlay
  @image
end

#icc_profile(path) ⇒ Object

Applies an ICC profile to the image. Requires path which is a path to a file containing a valid ICC profile.

img.icc_profile 'srgb.icc'



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 142

def icc_profile path
  profile = File.open( path ).readlines.join( '' ) if File.exist? path
  @image.profile! 'ICC', profile if profile
  @image
end

#icm_profile(path) ⇒ Object

Applies an ICM profile to the image. Requires path which is a path to a file containing a valid ICM profile.

img.icm_profile 'srgb.icm'



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 151

def icm_profile path
  profile = File.open( path ).readlines.join('') if File.exist? path
  @image.profile! 'ICM', profile if profile
  @image
end

#lighten(factor = 0.25) ⇒ Object

Lightens the image. Defaults to a blend factor of 25%.

img.lighten      # lightens the image 25%.
img.lighten 0.40 # lightens the image 40%.



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 73

def lighten factor = 0.25
  tint factor, factor, factor, '#ffffff'
end

#read(src) ⇒ Object

Read an image from a file specified by src and return a Magick::Image instance.



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 37

def read src
  Magick::Image.read( src ).first
end

#size_to_fit(dimensions) ⇒ Object

Resizes the image to fit within the constraints specified by dimensions where dimensions is a String in the format of ‘WIDTHxLENGTH’.

img.size_to_fit '64x64'



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 96

def size_to_fit dimensions
  @image.change_geometry dimensions do |w,h,img|
    img.density = '72x72'
    img.resize! w, h
    #             radius, sigma,  blend, threshold
    unsharp_mask  0.5,    1.0,    0.5,   0.25
  end
end

#tint(r, g, b, overlay) ⇒ Object

Tints the image according to the following parameters:

  • r Blending factor for the red channel

  • g Blending factor for the green channel

  • b Blending factor for the blue channel

  • overlay Color to tint the image img.tint 0.25, 0.25, 0.25, #ffffff # lightens the image 25%



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 54

def tint r, g, b, overlay
  @image = @image.colorize r, g, b, overlay
  @image
end

#unsharp_mask(rad = 0.5, sig = 1.0, blend = 0.5, thresh = 0.25) ⇒ Object

Sharpen only the edges of the image. Parameters are:

  • rad Radius: how big an edge can be

  • sig Sigma weight for gaussian: leave it at 1.0.

  • blend Blending factor: how much sharpening to apply as a percentage

  • thresh Threshold: how different 2 pixels must be to qualify as an edge img.unsharp_mask 0.5, 1.0, 0.5, 0.25



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 65

def unsharp_mask rad = 0.5, sig = 1.0, blend = 0.5, thresh = 0.25
  @image = @image.unsharp_mask rad, sig, blend, thresh
  @image
end

#write(target) ⇒ Object

Write the image to a specified path, target.



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# File 'lib/asset_compiler/rmagick_transformation_script.rb', line 42

def write target
  @image.write target do
    quality = 95
  end
end