Add resize_to_cover (#120)

* Add resize_to_cover

* Add an initial resize_to_cover test

* Fix method name and add passing tests for VIPS

* Add cover method for MiniMagick and add tests

* Rearrange VIPS tests to match source code order

* Update CHANGELOG.md

* Add documentation for cover to both engines

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 * [minimagick] Don't allow calling Kernel options via `loader`/`saver` options (@janko)
 
+* Add `#cover` that allows one to resize an image to cover a given width and height without cropping
+  the excess. (@brendon)
+
 ## 1.12.2 (2022-03-01)
 
 * Prevent remote shell execution when using `#apply` with operations coming from user input (@janko)

doc/minimagick.md

@@ -15,6 +15,7 @@ the [MiniMagick] gem (which is installed with the image_processing gem).
   * [`#resize_to_fit`](#resize_to_fit)
   * [`#resize_to_fill`](#resize_to_fill)
   * [`#resize_and_pad`](#resize_and_pad)
+  * [`#cover`](#cover)
   * [`#crop`](#crop)
   * [`#rotate`](#rotate)
   * [`#composite`](#composite)
@@ -189,6 +190,19 @@ It accepts `:gravity` for specifying the [gravity] to apply while cropping
 pipeline.resize_and_pad!(400, 400, gravity: "north-west")
 ```
 
+#### `#cover`
+
+Resizes the image to cover the specified dimensions while retaining the
+original aspect ratio. The overflowing areas will not be cropped.
+
+```rb
+pipeline = ImageProcessing::MiniMagick.source(image) # 600x800
+
+result = pipeline.cover!(300, 300)
+
+MiniMagick::Image.new(result.path).dimensions #=> [300, 400]
+```
+
 #### `#crop`
 
 Extracts an area from an image. The first two arguments are left & top edges of

doc/vips.md

@@ -14,6 +14,7 @@ The `ImageProcessing::Vips` module contains processing macros that use the
   * [`#resize_to_fit`](#resize_to_fit)
   * [`#resize_to_fill`](#resize_to_fill)
   * [`#resize_and_pad`](#resize_and_pad)
+  * [`#cover`](#cover)
   * [`#crop`](#crop)
   * [`#rotate`](#rotate)
   * [`#composite`](#composite)
@@ -221,6 +222,27 @@ pipeline.resize_to_fill!(400, 400, linear: true)
 
 See [`vips_thumbnail()`] and [`vips_gravity()`] for more details.
 
+#### `#cover`
+
+Resizes the image to cover the specified dimensions while retaining the
+original aspect ratio. The overflowing areas will not be cropped.
+
+```rb
+pipeline = ImageProcessing::Vips.source(image) # 600x800
+
+result = pipeline.cover!(300, 300)
+
+Vips::Image.new_from_file(result.path).size #=> [300, 400]
+```
+
+Any additional options (except `crop`) are forwarded to [`Vips::Image#thumbnail_image`]:
+
+```rb
+pipeline.cover!(400, 400, linear: true)
+```
+
+See [`vips_thumbnail()`] for more details.
+
 #### `#crop`
 
 Extracts an area from an image. The first two arguments are left & top edges of

lib/image_processing/mini_magick.rb

@@ -86,6 +86,12 @@ def resize_and_pad(width, height, background: :transparent, gravity: "Center", *
         magick.extent "#{width}x#{height}"
       end
 
+      # Resizes the image to cover the specified dimensions, without
+      # cropping the excess.
+      def cover(width, height, **options)
+        thumbnail("#{width}x#{height}^", **options)
+      end
+
       # Crops the image with the specified crop points.
       def crop(*args)
         case args.count

lib/image_processing/vips.rb

@@ -90,6 +90,21 @@ def resize_and_pad(width, height, gravity: "centre", extend: nil, background: ni
         image.gravity(gravity, width, height, extend: extend, background: background)
       end
 
+      # Resizes the image to cover the specified dimensions, without
+      # cropping the excess.
+      def cover(width, height, **options)
+        image_ratio = Rational(image.width, image.height)
+        thumbnail_ratio = Rational(width, height)
+
+        if image_ratio > thumbnail_ratio
+          width = ::Vips::MAX_COORD
+        else
+          height = ::Vips::MAX_COORD
+        end
+
+        thumbnail(width, height, **options, crop: :none)
+      end
+
       # Rotates the image by an arbitrary angle.
       def rotate(degrees, **options)
         image.similarity(angle: degrees, **options)

test/mini_magick_test.rb

@@ -8,6 +8,7 @@
   before do
     @portrait  = fixture_image("portrait.jpg")
     @landscape = fixture_image("landscape.jpg")
+    @square = fixture_image("square.jpg")
   end
 
   it "applies imagemagick operations" do
@@ -366,6 +367,61 @@
     end
   end
 
+  describe "#cover" do
+    before do
+      @portrait_pipeline = ImageProcessing::MiniMagick.source(@portrait)
+      @landscape_pipeline = ImageProcessing::MiniMagick.source(@landscape)
+      @square_pipeline = ImageProcessing::MiniMagick.source(@square)
+    end
+
+    it "resizes the portrait image to fill out the given landscape dimensions" do
+      assert_dimensions [300, 400], @portrait_pipeline.cover!(300, 200)
+    end
+
+    it "resizes the portrait image to fill out the given portrait dimensions" do
+      assert_dimensions [225, 300], @portrait_pipeline.cover!(200, 300)
+    end
+
+    it "resizes the portrait image to fill out the given square dimensions" do
+      assert_dimensions [300, 400], @portrait_pipeline.cover!(300, 300)
+    end
+
+    it "resizes the landscape image to fill out the given portrait dimensions" do
+      assert_dimensions [400, 300], @landscape_pipeline.cover!(200, 300)
+    end
+
+    it "resizes the landscape image to fill out the given landscape dimensions" do
+      assert_dimensions [300, 225], @landscape_pipeline.cover!(300, 200)
+    end
+
+    it "resizes the landscape image to fill out the given square dimensions" do
+      assert_dimensions [400, 300], @landscape_pipeline.cover!(300, 300)
+    end
+
+    it "resizes the square image to fill out the given portrait dimensions" do
+      assert_dimensions [300, 300], @square_pipeline.cover!(200, 300)
+    end
+
+    it "resizes the square image to fill out the given landscape dimensions" do
+      assert_dimensions [300, 300], @square_pipeline.cover!(300, 200)
+    end
+
+    it "resizes the square image to fill out the given square dimensions" do
+      assert_dimensions [300, 300], @square_pipeline.cover!(300, 300)
+    end
+
+    it "produces correct image" do
+      expected = fixture_image("cover.jpg")
+      assert_similar expected, @portrait_pipeline.cover!(300, 200)
+    end
+
+    it "accepts sharpening options" do
+      sharpened = @portrait_pipeline.cover!(400, 400, sharpen: { sigma: 1 })
+      normal    = @portrait_pipeline.cover!(400, 400, sharpen: false)
+      assert sharpened.size > normal.size, "Expected sharpened thumbnail to have bigger filesize than not sharpened thumbnail"
+    end
+  end
+
   describe "#crop" do
     before do
       @pipeline = ImageProcessing::MiniMagick.source(@portrait)

test/vips_test.rb

@@ -6,6 +6,7 @@
   before do
     @portrait  = fixture_image("portrait.jpg")
     @landscape = fixture_image("landscape.jpg")
+    @square = fixture_image("square.jpg")
   end
 
   it "applies vips operations" do
@@ -322,6 +323,72 @@
     end
   end
 
+  describe "#cover" do
+    before do
+      @portrait_pipeline = ImageProcessing::Vips.source(@portrait)
+      @landscape_pipeline = ImageProcessing::Vips.source(@landscape)
+      @square_pipeline = ImageProcessing::Vips.source(@square)
+    end
+
+    it "resizes the portrait image to fill out the given landscape dimensions" do
+      assert_dimensions [300, 400], @portrait_pipeline.cover!(300, 200)
+    end
+
+    it "resizes the portrait image to fill out the given portrait dimensions" do
+      assert_dimensions [225, 300], @portrait_pipeline.cover!(200, 300)
+    end
+
+    it "resizes the portrait image to fill out the given square dimensions" do
+      assert_dimensions [300, 400], @portrait_pipeline.cover!(300, 300)
+    end
+
+    it "resizes the landscape image to fill out the given portrait dimensions" do
+      assert_dimensions [400, 300], @landscape_pipeline.cover!(200, 300)
+    end
+
+    it "resizes the landscape image to fill out the given landscape dimensions" do
+      assert_dimensions [300, 225], @landscape_pipeline.cover!(300, 200)
+    end
+
+    it "resizes the landscape image to fill out the given square dimensions" do
+      assert_dimensions [400, 300], @landscape_pipeline.cover!(300, 300)
+    end
+
+    it "resizes the square image to fill out the given portrait dimensions" do
+      assert_dimensions [300, 300], @square_pipeline.cover!(200, 300)
+    end
+
+    it "resizes the square image to fill out the given landscape dimensions" do
+      assert_dimensions [300, 300], @square_pipeline.cover!(300, 200)
+    end
+
+    it "resizes the square image to fill out the given square dimensions" do
+      assert_dimensions [300, 300], @square_pipeline.cover!(300, 300)
+    end
+
+    it "produces correct image" do
+      expected = fixture_image("cover.jpg")
+      assert_similar expected, @portrait_pipeline.cover!(300, 200)
+    end
+
+    it "accepts thumbnail options except :crop" do
+      attention = @portrait_pipeline.cover!(400, 400, crop: :attention)
+      centre    = @portrait_pipeline.cover!(400, 400, crop: :centre)
+      assert_similar centre, attention
+    end
+
+    it "accepts sharpening options" do
+      sharpened = @portrait_pipeline.cover!(400, 400, sharpen: ImageProcessing::Vips::Processor::SHARPEN_MASK)
+      normal   = @portrait_pipeline.cover!(400, 400, sharpen: false)
+      assert sharpened.size > normal.size, "Expected sharpened thumbnail to have bigger filesize than not sharpened thumbnail"
+    end
+
+    it "sharpening uses integer precision" do
+      sharpened = @portrait_pipeline.cover(400, 400).call(save: false)
+      assert_equal :uchar, sharpened.format
+    end
+  end
+
   describe "#rotate" do
     before do
       @pipeline = ImageProcessing::Vips.source(@portrait)