Crop and resize an image using MiniMagick in Ruby on Rails. Two approaches.

resize_nocrop_noscale

  def resize_nocrop_noscale(image, w,h)
    w_original = image[:width].to_f
    h_original = image[:height].to_f

    if w_original < w && h_original < h
      return image
    end

    # resize
    image.resize("#{w}x#{h}")

    return image
  end

resize_with_crop

  def resize_with_crop(img, w, h, options = {})
    gravity = options[:gravity] || :center

    w_original, h_original = [img[:width].to_f, img[:height].to_f]

    op_resize = ''

    # check proportions
    if w_original * h < h_original * w
      op_resize = "#{w.to_i}x"
      w_result = w
      h_result = (h_original * w / w_original)
    else
      op_resize = "x#{h.to_i}"
      w_result = (w_original * h / h_original)
      h_result = h
    end

    w_offset, h_offset = crop_offsets_by_gravity(gravity, [w_result, h_result], [ w, h])

    img.combine_options do |i|
      i.resize(op_resize)
      i.gravity(gravity)
      i.crop "#{w.to_i}x#{h.to_i}+#{w_offset}+#{h_offset}!"
    end

    img
  end

  # from http://www.dweebd.com/ruby/resizing-and-cropping-images-to-fixed-dimensions/

  GRAVITY_TYPES = [ :north_west, :north, :north_east, :east, :south_east, :south, :south_west, :west, :center ]

  def crop_offsets_by_gravity(gravity, original_dimensions, cropped_dimensions)
    raise(ArgumentError, "Gravity must be one of #{GRAVITY_TYPES.inspect}") unless GRAVITY_TYPES.include?(gravity.to_sym)
    raise(ArgumentError, "Original dimensions must be supplied as a [ width, height ] array") unless original_dimensions.kind_of?(Enumerable) && original_dimensions.size == 2
    raise(ArgumentError, "Cropped dimensions must be supplied as a [ width, height ] array") unless cropped_dimensions.kind_of?(Enumerable) && cropped_dimensions.size == 2

    original_width, original_height = original_dimensions
    cropped_width, cropped_height = cropped_dimensions

    vertical_offset = case gravity
      when :north_west, :north, :north_east then 0
      when :center, :east, :west then [ ((original_height - cropped_height) / 2.0).to_i, 0 ].max
      when :south_west, :south, :south_east then (original_height - cropped_height).to_i
    end

    horizontal_offset = case gravity
      when :north_west, :west, :south_west then 0
      when :center, :north, :south then [ ((original_width - cropped_width) / 2.0).to_i, 0 ].max
      when :north_east, :east, :south_east then (original_width - cropped_width).to_i
    end

    return [ horizontal_offset, vertical_offset ]
  end

resize_with_nocrop

# see details - http://maxivak.com/crop-and-resize-an-image-using-minimagick-ruby-on-rails

def resize_with_nocrop(image, w, h)

    w_original = image[:width].to_f
    h_original = image[:height].to_f

    if (w_original*h != h_original * w)
      if w_original*h >= h_original * w
        # long width
        w_result = w
        h_result = w_result * (h_original / w_original)
      elsif w_original*h <= h_original * w
        # long height
        h_result = h
        w_result = h_result * (w_original / h_original)
      end
    else
       # good proportions
       h_result = h
       w_result = w
    end

    #
    image.resize("#{w_result}x#{h_result}")
    return image
  end

@maxivak I believe that in the resize_with_crop method, there is a mistake respect to the original code that you mentioned.

The fact that the line 23 in the gravity function there is not always 'Northwest' but the option gravity that we pass, mess up the cropping region. Effectively if you try your code without gravity option, it will set it up that to :center, and the cropping result will be just not around the center but starting from the bottom of the image, and that is weird.
What do you think?

Actually I just think that condition is completely wrong. It shouldn't have any gravity before crop (the gravity anyway is used to calculate the offset). Using a gravity flag that is not fixed as for example the original code 'NorthWest', will just create a lot of trouble in the image cropping: e.g. don't give option will set the option gravity to center, and with the gravity as center before the crop image, it will move it to the bottom.

I believe that you can be without any gravity before the crop, or if you want one just put it as fixed value as 'NorthWest'.

My 2 cents!

Cheers

Awesome script, thanks.

Btw, this didn’t maintain the correct gravity orientation for me when I used this exact code for the resize_with_crop function.

I needed to remove the:

i.gravity(gravity)

line of code to make it work.

Doesn't work properly. Two strings works wrong in my case. Should be:
when :center, :east, :west then [ ((original_height - cropped_height) / 2.0).to_i, 0 ].min
when :center, :north, :south then [ ((original_width - cropped_width) / 2.0).to_i, 0 ].min

@Sinozet THANK YOU