Fetch the resized image

Instead of getting the full size image, the image can be fetched with a
width and height parameter so that only the resized data is
transferred. The url looks like this:

https://cdn-images-1.medium.com/fit/c/<width>/<height>/<media-id>

I picked a max image width of 800px. If the image width is more than
that, it scales the width down to 800, then applies that ratio to the
height. If it's smaller than that, the image is displayed as the
original.

spec/classes/paragraph_converter_spec.cr

@@ -180,14 +180,14 @@ describe ParagraphConverter do
         "layout": "INSET_CENTER",
         "metadata": {
           "id": "image.png",
-          "originalWidth": 618,
-          "originalHeight": 682
+          "originalWidth": 1000,
+          "originalHeight": 600
         }
       }
     JSON
     expected = [
       Figure.new(children: [
-        Image.new(src: "image.png"),
+        Image.new(src: "image.png", originalWidth: 1000, originalHeight: 600),
         FigureCaption.new(children: [
           Text.new("Image by "),
           Anchor.new(href: "https://unsplash.com/@someuser", text: "someuser"),
@@ -303,7 +303,7 @@ describe ParagraphConverter do
       UnorderedList.new([ListItem.new([Text.new("text")] of Child)] of Child),
       OrderedList.new([ListItem.new([Text.new("text")] of Child)] of Child),
       Figure.new(children: [
-        Image.new(src: "1*miroimage.png"),
+        Image.new(src: "1*miroimage.png", originalWidth: 618, originalHeight: 682),
         FigureCaption.new(children: [Text.new("text")] of Child),
       ] of Child),
       IFrame.new(href: "https://example.com"),

spec/components/page_content_spec.cr

@@ -90,7 +90,7 @@ describe PageContent do
   it "renders a figure and figure caption" do
     page = Page.new(nodes: [
       Figure.new(children: [
-        Image.new(src: "image.png"),
+        Image.new(src: "image.png", originalWidth: 100, originalHeight: 100),
         FigureCaption.new(children: [
           Text.new("A caption")
         ] of Child),
@@ -101,7 +101,7 @@ describe PageContent do
 
     html.should eq stripped_html <<-HTML
       <figure>
-        <img src="https://cdn-images-1.medium.com/image.png">
+        <img src="https://cdn-images-1.medium.com/fit/c/100/100/image.png" width="100" height="100">
         <figcaption>A caption</figcaption>
       </figure>
     HTML
@@ -134,13 +134,17 @@ describe PageContent do
   it "renders an image" do
     page = Page.new(nodes: [
       Paragraph.new(children: [
-        Image.new(src: "image.png"),
+        Image.new(src: "image.png", originalWidth: 100, originalHeight: 100),
       ] of Child)
     ] of Child)
 
     html = PageContent.new(page: page).render_to_string
 
-    html.should eq %(<p><img src="https://cdn-images-1.medium.com/image.png"></p>)
+    html.should eq stripped_html <<-HTML
+      <p>
+        <img src="https://cdn-images-1.medium.com/fit/c/100/100/image.png" width="100" height="100">
+      </p>
+    HTML
   end
 
   it "renders an iframe container" do

spec/models/nodes_spec.cr

@@ -0,0 +1,18 @@
+require "../spec_helper"
+
+module Nodes
+  describe Image do
+    it "adjusts the width and height proportionally" do
+      image = Image.new(src: "image.png", originalWidth: 1000, originalHeight: 603)
+
+      image.width.should eq("800")
+      image.height.should eq("482")
+    end
+
+    it "includes the adjusted width and height in the src" do
+      image = Image.new(src: "image.png", originalWidth: 1000, originalHeight: 603)
+
+      image.src.should eq("https://cdn-images-1.medium.com/fit/c/800/482/image.png")
+    end
+  end
+end

src/classes/paragraph_converter.cr

@@ -77,7 +77,11 @@ class ParagraphConverter
     if metadata = paragraph.metadata
       caption_markup = MarkupConverter.convert(paragraph.text, paragraph.markups)
       Figure.new(children: [
-        Image.new(src: metadata.id),
+        Image.new(
+          src: metadata.id,
+          originalWidth: metadata.originalWidth,
+          originalHeight: metadata.originalHeight
+        ),
         FigureCaption.new(children: caption_markup)
       ] of Child)
     else

src/components/page_content.cr

@@ -63,7 +63,7 @@ class PageContent < BaseComponent
   end
 
   def render_child(child : Image)
-    img src: child.src
+    img src: child.src, width: child.width, height: child.height
   end
 
   def render_child(node : ListItem)

src/models/nodes.cr

@@ -79,18 +79,39 @@ module Nodes
   end
 
   class Image
-    IMAGE_HOST = "https://cdn-images-1.medium.com"
+    IMAGE_HOST = "https://cdn-images-1.medium.com/fit/c"
+    MAX_WIDTH = 800
 
-    getter src : String
+    getter originalHeight : Int32
+    getter originalWidth : Int32
 
-    def initialize(src : String)
-      @src = "#{IMAGE_HOST}/#{src}"
+    def initialize(@src : String, @originalWidth : Int32, @originalHeight : Int32)
     end
 
     def ==(other : Image)
       other.src == src
     end
 
+    def src
+      [IMAGE_HOST, width, height, @src].join("/")
+    end
+
+    def width
+      [originalWidth, MAX_WIDTH].min.to_s
+    end
+
+    def height
+      if originalWidth > MAX_WIDTH
+        (originalHeight * ratio).round.to_i.to_s
+      else
+        originalHeight.to_s
+      end
+    end
+
+    private def ratio
+      MAX_WIDTH / originalWidth
+    end
+
     def empty?
       false
     end