Module: Mindee::Image::ImageUtils

Defined in:
lib/mindee.rb,
lib/mindee/image/image_utils.rb

Overview

Miscellaneous image operations.

Class Method Summary collapse

Class Method Details

.calculate_dimensions_from_media_box(image, media_box) ⇒ Array<Integer>

Computes the Height & Width from a page’s media box. Falls back to the size of the initial image.

Parameters:

  • image (MiniMagick::Image) —

    The initial image that will fit into the page.

  • media_box (Array<Integer>, nil)

Returns:

  • (Array<Integer>) 


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# File 'lib/mindee/image/image_utils.rb', line 81

def self.calculate_dimensions_from_media_box(image, media_box)
  if !media_box.nil? && media_box.any?
    [
      media_box[2]&.to_i || image[:width].to_i,
      media_box[3]&.to_i || image[:height].to_i,
    ]
  else
    [image[:width].to_i, image[:height].to_i]
  end
end

.calculate_new_dimensions(original, max_width: nil, max_height: nil) ⇒ Object

Computes the new dimensions for a given SKBitmap, and returns a scaled down version of it relative to the provided bounds.

Parameters:

  • original (MiniMagick::Image) —

    Input MiniMagick image.

  • max_width (Integer) (defaults to: nil) —

    Maximum width. If not specified, the horizontal ratio will remain the same.

  • max_height (Integer) (defaults to: nil) —

    Maximum height. If not specified, the vertical ratio will remain the same.



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# File 'lib/mindee/image/image_utils.rb', line 61

def self.calculate_new_dimensions(original, max_width: nil, max_height: nil)
  raise 'Provided image could not be processed for resizing.' if original.nil?

  return [original.width, original.height] if max_width.nil? && max_height.nil?

  width_ratio = max_width ? max_width.to_f / original.width : Float::INFINITY
  height_ratio = max_height ? max_height.to_f / original.height : Float::INFINITY

  scale_factor = [width_ratio, height_ratio].min

  new_width = (original.width * scale_factor).to_i
  new_height = (original.height * scale_factor).to_i

  [new_width, new_height]
end

.compress_image_quality(image, quality) ⇒ Object

Compresses the quality of the provided MiniMagick image.

Parameters:

  • image (MiniMagick::Image) —

    MiniMagick image handle.

  • quality (Integer) —

    Quality to apply to the image. This is independent of a JPG’s base quality.



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# File 'lib/mindee/image/image_utils.rb', line 25

def self.compress_image_quality(image, quality)
  image.quality quality.to_s
end

.image_to_stringio(image, format = 'JPEG') ⇒ StringIO

Converts a StringIO containing an image into a MiniMagick image.

Parameters:

  • image (MiniMagick::Image) —

    the input image.

  • format (String) (defaults to: 'JPEG') —

    Format parameter, left open for the future, but should be JPEG for current use-cases.

Returns:

  • (StringIO) 


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# File 'lib/mindee/image/image_utils.rb', line 47

def self.image_to_stringio(image, format = 'JPEG')
  image.format format
  blob = image.to_blob
  stringio = StringIO.new(blob)
  stringio.rewind

  stringio
end

.pdf_to_magick_image(pdf_stream, image_quality) ⇒ MiniMagick::Image

Transforms a PDF into a MagickImage. This is currently used for single-page PDFs.

Parameters:

  • pdf_stream (StringIO) —

    Input stream.

  • image_quality (Integer) —

    Quality to apply to the image.

Returns:

  • (MiniMagick::Image) 


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# File 'lib/mindee/image/image_utils.rb', line 96

def self.pdf_to_magick_image(pdf_stream, image_quality)
  compressed_image = MiniMagick::Image.read(pdf_stream.read)
  compressed_image.format('jpg')
  compressed_image.quality image_quality.to_s
  compressed_image
end

.resize_image(image, width, height) ⇒ Object

Resizes a provided MiniMagick Image with the given width & height, if present.

Parameters:

  • image (MiniMagick::Image) —

    MiniMagick image handle.

  • width (Integer) —

    Width to comply with.

  • height (Integer) —

    Height to comply with.



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# File 'lib/mindee/image/image_utils.rb', line 12

def self.resize_image(image, width, height)
  if width && height
    image.resize "#{width}x#{height}"
  elsif width
    image.resize width.to_s
  elsif height
    image.resize "x#{height}"
  end
end

.to_image(image) ⇒ MiniMagick::Image

Mostly here so that IDEs don’t get confused on the type (@type annotation fails sometimes.)

Parameters:

  • image (MiniMagick::Image, StringIO, File, Tempfile) —

    The input image

Returns:

  • (MiniMagick::Image) 


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# File 'lib/mindee/image/image_utils.rb', line 32

def self.to_image(image)
  if image.respond_to?(:read) && image.respond_to?(:rewind)
    image.rewind
    MiniMagick::Image.read(image)
  elsif image.is_a?(MiniMagick::Image)
    image
  else
    raise "Expected an I/O object or a MiniMagick::Image. '#{image.class}' given instead."
  end
end