From 952ed806ac733a66a400bd7db394ebcaf4f5f24f Mon Sep 17 00:00:00 2001
From: Jelle-S <sebreghts.jelle@gmail.com>
Date: Wed, 16 Sep 2015 17:32:21 +0200
Subject: [PATCH 1/2] Add support for derivatives

---
 .../Grav/Common/Page/Medium/ImageMedium.php   | 43 +++++++++++++++++--
 1 file changed, 39 insertions(+), 4 deletions(-)

diff --git a/system/src/Grav/Common/Page/Medium/ImageMedium.php b/system/src/Grav/Common/Page/Medium/ImageMedium.php
index 17fd32151..c50cbf43f 100644
--- a/system/src/Grav/Common/Page/Medium/ImageMedium.php
+++ b/system/src/Grav/Common/Page/Medium/ImageMedium.php
@@ -56,6 +56,11 @@ class ImageMedium extends Medium
         'zoomCrop' => [ 0, 1 ]
     ];
 
+    /**
+     * @var array
+     */
+    protected $derivatives = [];
+
     /**
      * Construct.
      *
@@ -157,22 +162,52 @@ class ImageMedium extends Medium
      */
     public function srcset($reset = true)
     {
-        if (empty($this->alternatives)) {
+        if (empty($this->alternatives) && empty($this->derivatives)) {
             if ($reset) {
                 $this->reset();
             }
             return '';
         }
 
-        $srcset = [ $this->url($reset) . ' ' . $this->get('width') . 'w' ];
+        if (!empty($this->derivatives)) {
+          asort($this->derivatives);
 
-        foreach ($this->alternatives as $ratio => $medium) {
-            $srcset[] = $medium->url($reset) . ' ' . $medium->get('width') . 'w';
+          foreach ($this->derivatives as $url => $width) {
+              $srcset[] = $url . ' ' . $width . 'w';
+          }
+
+          $srcset[] = $this->url($reset) . ' ' . $this->get('width') . 'w';
+        }
+        else {
+          $srcset = [ $this->url($reset) . ' ' . $this->get('width') . 'w' ];
+          foreach ($this->alternatives as $ratio => $medium) {
+              $srcset[] = $medium->url($reset) . ' ' . $medium->get('width') . 'w';
+          }
         }
 
         return implode(', ', $srcset);
     }
 
+    public function derivatives($min_width, $max_width, $step = 200) {
+      $width = $min_width;
+      if ($max_width > $this->get('width')) {
+        $max_width = $this->get('width');
+      }
+      while($width <= $max_width) {
+        $ratio = $width / $this->get('width');
+        $derivative = MediumFactory::scaledFromMedium($this, 1, $ratio);
+        if (is_array($derivative)) {
+          $this->addDerivative($derivative['file']);
+        }
+        $width += $step;
+      }
+      return $this;
+    }
+
+    public function addDerivative(ImageMedium $image) {
+      $this->derivatives[$image->url()] = $image->get('width');
+    }
+
     /**
      * Parsedown element for source display mode
      *

From 9c0525f292235929804a13147cc57908c0b5843d Mon Sep 17 00:00:00 2001
From: Peter Droogmans <peter@attiks.com>
Date: Wed, 16 Sep 2015 17:41:26 +0200
Subject: [PATCH 2/2] Add comments

---
 .../Grav/Common/Page/Medium/ImageMedium.php    | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/system/src/Grav/Common/Page/Medium/ImageMedium.php b/system/src/Grav/Common/Page/Medium/ImageMedium.php
index c50cbf43f..017c40e19 100644
--- a/system/src/Grav/Common/Page/Medium/ImageMedium.php
+++ b/system/src/Grav/Common/Page/Medium/ImageMedium.php
@@ -188,12 +188,23 @@ class ImageMedium extends Medium
         return implode(', ', $srcset);
     }
 
+    /**
+     * Generate derivatives
+     *
+     * @param  int $min_width
+     * @param  int $max_width
+     * @param  int $step
+     * @return $this
+     */
     public function derivatives($min_width, $max_width, $step = 200) {
       $width = $min_width;
+
+      // Do not upscale images.
       if ($max_width > $this->get('width')) {
         $max_width = $this->get('width');
       }
-      while($width <= $max_width) {
+
+      while ($width <= $max_width) {
         $ratio = $width / $this->get('width');
         $derivative = MediumFactory::scaledFromMedium($this, 1, $ratio);
         if (is_array($derivative)) {
@@ -204,6 +215,11 @@ class ImageMedium extends Medium
       return $this;
     }
 
+    /**
+     * Add a derivative
+     *
+     * @param  ImageMedium $image
+     */
     public function addDerivative(ImageMedium $image) {
       $this->derivatives[$image->url()] = $image->get('width');
     }