feat: add cropping via vips

The difference in reference images:
- plasma-cropped-excessive-size - MAE (mean average error): 0.00950674
- plasma-cropped - MAE: 0.0107107
- plasma-cropped-negative-initial-coords - MAE: 0.00959682
- plasma-cropped-1x1 - no difference, duplicated in vips directory for completeness

Libvips crop output appears a bit more noisy, but it seems to better resemble the original

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Added
 - Vips image processor (resizing)
 - Vips colour filters
+- Vips crop
 
 ### Removed
 - [BREAKING] dropped support for a broken 'dominant' border colour

lib/morandi/crop_utils.rb

@@ -91,5 +91,40 @@ def apply_crop(pixbuf, x_coord, y_coord, width, height, fill_col = 0xffffffff)
       end
       pixbuf
     end
+
+    def apply_crop_vips(img, x_coord, y_coord, width, height)
+      if x_coord.negative? ||
+         y_coord.negative? ||
+         ((x_coord + width) > img.width) ||
+         ((y_coord + height) > img.height)
+
+        extract_area_x = [0, x_coord].max
+        extract_area_y = [0, y_coord].max
+        area_to_copy = img.extract_area(extract_area_x, extract_area_y, img.width - extract_area_x,
+                                        img.height - extract_area_y)
+
+        fill_colour = [255, 255, 255]
+        pixel = (Vips::Image.black(1, 1).colourspace(:srgb) + fill_colour).cast(img.format)
+        canvas = pixel.embed 0, 0, width, height, extend: :copy
+        canvas = canvas.copy xres: img.xres, yres: img.yres
+
+        cropped = canvas.composite(area_to_copy, :over, x: [-x_coord, 0].max,
+                                                        y: [-y_coord, 0].max,
+                                                        compositing_space: area_to_copy.interpretation)
+
+        # Because image is drawn on an opaque white, alpha doesn't matter at this point anyway, so let's strip the
+        # alpha channel from the output. According to #composite docs, the resulting image always has alpha channel,
+        # but I added a guard to avoid regressions if that ever changes.
+        cropped = cropped.extract_band(0, n: cropped.bands - 1) if cropped.has_alpha?
+        cropped
+      else
+        x_coord = x_coord.clamp(0, img.width)
+        y_coord = y_coord.clamp(0, img.height)
+        width = width.clamp(1, img.width - x_coord)
+        height = height.clamp(1, img.height - y_coord)
+
+        img.crop(x_coord, y_coord, width, height)
+      end
+    end
   end
 end

lib/morandi/vips_image_processor.rb

@@ -60,6 +60,7 @@ def process!
         @scale = 1.0
       end
 
+      apply_crop!
       apply_filters!
 
       return unless @options['output.limit'] && @output_width && @output_height
@@ -82,6 +83,24 @@ def write_to_jpeg(write_to, quality = nil)
 
     private
 
+    def apply_crop!
+      crop = @options['crop']
+
+      return if crop.nil? && @options['image.auto-crop'].eql?(false)
+
+      crop = crop.split(',').map(&:to_i) if crop.is_a?(String) && crop =~ /^\d+,\d+,\d+,\d+/
+
+      crop = nil unless crop.is_a?(Array) && crop.size.eql?(4) && crop.all? do |i|
+        i.is_a?(Numeric)
+      end
+      # can't crop, won't crop
+      return if @output_width.nil? && @output_height.nil? && crop.nil?
+
+      crop = crop.map { |s| (s.to_f * @scale).floor } if crop && not_equal_to_one(@scale)
+      crop ||= Morandi::CropUtils.autocrop_coords(@img.width, @img.height, @output_width, @output_height)
+      @img = Morandi::CropUtils.apply_crop_vips(@img, crop[0], crop[1], crop[2], crop[3])
+    end
+
     def apply_filters!
       filter_name = @options['fx']
       return unless SUPPORTED_FILTERS.include?(filter_name)

spec/morandi_spec.rb

@@ -87,7 +87,7 @@
       end
     end
 
-    describe 'with a big image and a bigger cropped area to fill', vips_wip: processor_name == 'vips' do
+    describe 'with a big image and a bigger cropped area to fill' do
       let(:options) do
         {
           'crop' => '0,477,15839,18804',
@@ -148,7 +148,7 @@
       end
     end
 
-    context 'when give a "crop" option', vips_wip: processor_name == 'vips' do
+    context 'when give a "crop" option' do
       let(:cropped_width) { 300 }
       let(:cropped_height) { 300 }
 
@@ -162,7 +162,7 @@
           expect(processed_image_width).to eq(cropped_width)
           expect(processed_image_height).to eq(cropped_height)
 
-          expect(file_out).to match_reference_image('plasma-cropped')
+          expect(file_out).to match_reference_image(reference_image_prefix, 'plasma-cropped')
         end
       end
 
@@ -176,7 +176,7 @@
           expect(processed_image_width).to eq(cropped_width)
           expect(processed_image_height).to eq(cropped_height)
 
-          expect(file_out).to match_reference_image('plasma-cropped')
+          expect(file_out).to match_reference_image(reference_image_prefix, 'plasma-cropped')
         end
       end
 
@@ -190,7 +190,7 @@
           expect(processed_image_width).to eq(cropped_width)
           expect(processed_image_height).to eq(cropped_height)
 
-          expect(file_out).to match_reference_image('plasma-cropped-negative-initial-coords')
+          expect(file_out).to match_reference_image(reference_image_prefix, 'plasma-cropped-negative-initial-coords')
         end
       end
 
@@ -204,7 +204,7 @@
           expect(processed_image_width).to eq(original_image_width + 50)
           expect(processed_image_height).to eq(original_image_height + 50)
 
-          expect(file_out).to match_reference_image('plasma-cropped-excessive-size')
+          expect(file_out).to match_reference_image(reference_image_prefix, 'plasma-cropped-excessive-size')
         end
       end
 
@@ -218,7 +218,7 @@
           expect(processed_image_width).to eq(1)
           expect(processed_image_height).to eq(1)
 
-          expect(file_out).to match_reference_image('plasma-cropped-1x1')
+          expect(file_out).to match_reference_image(reference_image_prefix, 'plasma-cropped-1x1')
         end
       end
     end