fix: Reject sub-pixel resizes and wrap vips errors

lib/dynamic_image/errors.rb

@@ -33,6 +33,7 @@ class InvalidSignature < DynamicImage::Errors::Error; end
     # the size works out to less than a pixel, as <tt>"0x0"</tt> does, or <tt>"1x1"</tt> against a very wide image.
     #
     # @see DynamicImage::ImageSizing#fit
+    # @see DynamicImage::Model::Transformations#resize
     class InvalidSizeOptions < DynamicImage::Errors::Error; end
 
     # Raised when a transformation can't be applied, either because a rotation isn't a multiple of 90 degrees or

lib/dynamic_image/model/transformations.rb

@@ -17,9 +17,11 @@ module Transformations
       # @param max_size [Vector2d, String] the size to fit within, either a vector or a <tt>"{width}x{height}"</tt>
       #   string. Either dimension may be omitted to scale by the other alone.
       # @return [self]
+      # @raise [DynamicImage::Errors::InvalidSizeOptions] if the result is less than a pixel in either dimension
+      # @raise [DynamicImage::Errors::InvalidImage] if the stored data can't be processed
       def resize(max_size)
         transform_image do |image|
-          resized = image.resize(real_size.fit(max_size))
+          resized = image.resize(fit_size(max_size))
           scale_crop(resized.size)
           resized
         end
@@ -30,6 +32,7 @@ def resize(max_size)
       # @param degrees [Integer] the angle, which must be a multiple of 90. Rotating by 0 is a no-op.
       # @return [self]
       # @raise [DynamicImage::Errors::InvalidTransformation] if the angle isn't a multiple of 90
+      # @raise [DynamicImage::Errors::InvalidImage] if the stored data can't be processed
       #
       # @example
       #   image.rotate(90)
@@ -52,6 +55,16 @@ def rotate(degrees = 90)
 
       private
 
+      # Scales +max_size+ against the image, rejecting a result smaller than a pixel in either dimension, as
+      # {DynamicImage::ImageSizing#fit} does for the sizes rendered on request.
+      def fit_size(max_size)
+        new_size = real_size.fit(max_size)
+        return new_size if new_size.x >= 1 && new_size.y >= 1
+
+        raise DynamicImage::Errors::InvalidSizeOptions,
+              "#{new_size} has a dimension smaller than one pixel"
+      end
+
       def scale_crop(new_size)
         scale = new_size.to_f_vector / real_size
 
@@ -121,6 +134,8 @@ def transform_image(&block)
         end
         read_image_metadata
         self
+      rescue Vips::Error => e
+        raise DynamicImage::Errors::InvalidImage, e.message
       end
     end
   end

spec/dynamic_image/model/transformations_spec.rb

@@ -77,6 +77,27 @@
         expect(resized.crop_gravity).to eq(Vector2d(1, 1))
       end
     end
+
+    context "when the size is smaller than a pixel" do
+      subject(:resized) { image.resize("0x0") }
+
+      it "raises an error" do
+        expect { resized }.to(
+          raise_error(DynamicImage::Errors::InvalidSizeOptions)
+        )
+      end
+    end
+
+    context "when vips fails to process the data" do
+      before do
+        allow(DynamicImage::ImageProcessor)
+          .to receive(:new).and_raise(Vips::Error, "unable to read")
+      end
+
+      it "raises an error" do
+        expect { resized }.to raise_error(DynamicImage::Errors::InvalidImage)
+      end
+    end
   end
 
   describe "#rotate" do
@@ -96,6 +117,17 @@
       end
     end
 
+    context "when vips fails to process the data" do
+      before do
+        allow(DynamicImage::ImageProcessor)
+          .to receive(:new).and_raise(Vips::Error, "unable to read")
+      end
+
+      it "raises an error" do
+        expect { rotated }.to raise_error(DynamicImage::Errors::InvalidImage)
+      end
+    end
+
     context "with a 90 degree rotation" do
       it "rotates the image" do
         expect(rotated.real_size).to eq(Vector2d.new(200, 320))