handling dimensions that are too large

app/models/projection.rb

@@ -112,7 +112,7 @@ def image_source
   end
 
   def real_transformation
-    return transformation unless image.is_a? RestrictedImage
+    return transformation unless (image.is_a? RestrictedImage) || use_original_size?
 
     IIIF::Image::Transformation.new(
       region: transformation.region,
@@ -127,7 +127,7 @@ def restricted_size
     size = transformation.size
     case size
     when IIIF::Image::Size::BestFit
-      max_size = image.max_size(self)
+      max_size = max_image_size
       if size.width <= max_size.width && size.height <= max_size.height
         size
       else
@@ -139,4 +139,25 @@ def restricted_size
       size
     end
   end
+
+  # For a full image request, if the requested width and height are larger than the original image,
+  # this method will return true
+  def use_original_size?
+    size = transformation.size
+    max_size = image.max_tile_dimensions.call(self)
+    (size.is_a? IIIF::Image::Size::BestFit) && max_size.width < size.width && max_size.height < size.height
+  end
+
+  # The original restricted image function used max_size, but the StacksImage class does not have that method
+  # Since we are using the restricted image block for both RestrictedImage and StacksImage, we check
+  # which method is available
+  def max_image_size
+    image.respond_to?(:max_size) ? image.max_size(self) : dimensions_to_size(image.max_tile_dimensions.call(self))
+  end
+
+  # StacksImage has max_tile_dimensions, which returns dimensions
+  # We need to create a Size object in order to pass back to create the Iiif image object for image_source
+  def dimensions_to_size(dimensions)
+    IIIF::Image::Size::BestFit.new(dimensions.width, dimensions.height)
+  end
 end

spec/models/projection_spec.rb

@@ -20,7 +20,7 @@
     end
   end
 
-  describe '#tile_dimensions' do
+  describe '#tiledimensions' do
     subject { instance.send(:tile_dimensions) }
 
     context "for an unrestricted image" do
@@ -112,6 +112,18 @@
           expect(http_client).to have_received(:get).with(%r{/full/max/0/default.jpg})
         end
       end
+
+      context "best fit size" do
+        let(:options) { { size: '!850,700', region: 'full' } }
+
+        it 'returns original size when requested dimensions are larger' do
+          allow(HTTP).to receive(:use)
+            .and_return(http_client)
+          allow(http_client).to receive(:get).and_return(double(body: nil))
+          subject.response
+          expect(http_client).to have_received(:get).with(%r{/full/!800,600/0/default.jpg})
+        end
+      end
     end
 
     context 'for a restricted image' do