add filter to perform a relative resize, thus keeping the aspect ratio, and not exceeding a max width and a max height

Imagine/Filter/Loader/TwoWayRelativeResizeFilterLoader.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Liip\ImagineBundle\Imagine\Filter\Loader;
+
+use Imagine\Image\ImageInterface;
+
+use Liip\ImagineBundle\Imagine\Filter\Loader\LoaderInterface;
+use Liip\ImagineBundle\Imagine\Filter\TwoWayRelativeResize;
+
+/**
+ * Loader for this bundle's two-way relative resize filter.
+ *
+ * @author      Robert-Jan Bijl <[email protected]>
+ */
+class TwoWayRelativeResizeFilterLoader implements LoaderInterface
+{
+    /**
+     * {@inheritDoc}
+     */
+    public function load(ImageInterface $image, array $options = array())
+    {
+        $newHeight = isset($options['height']) ? $options['height'] : null;
+        $newWidth = isset($options['width']) ? $options['width'] : null;
+
+        // if no resize is given, just return the original image
+        if (null === $newHeight && null === $newWidth) {
+            return $image;
+        }
+
+        $filter = new TwoWayRelativeResize($newHeight, $newWidth);
+        return $filter->apply($image);
+    }
+}

Imagine/Filter/TwoWayRelativeResize.php

@@ -0,0 +1,90 @@
+<?php
+
+namespace Liip\ImagineBundle\Imagine\Filter;
+
+use Imagine\Filter\FilterInterface;
+use Imagine\Image\Box;
+use Imagine\Image\ImageInterface;
+
+/**
+ * Filter for resizing an image, by keeping the aspect ratio and not exceeding the maxWidth and maxHeight parameters
+ *
+ * @author      Robert-Jan Bijl <[email protected]>
+ */
+class TwoWayRelativeResize implements FilterInterface
+{
+    /**
+     * @var int
+     */
+    private $newWidth;
+
+    /**
+     * @var int
+     */
+    private $newHeight;
+
+    /**
+     * Constructor
+     *
+     * @param int $newHeight
+     * @param int $newWidth
+     */
+    public function __construct($newHeight, $newWidth)
+    {
+        $this->newHeight = $newHeight;
+        $this->newWidth = $newWidth;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function apply(ImageInterface $image)
+    {
+        // if we don't have any new dimensions, return the original
+        if (null === $this->newHeight && null === $this->newWidth) {
+            return $image;
+        }
+
+        list($newWidth, $newHeight) = $this->calculateNewDimensions(
+            $image->getSize()->getWidth(),
+            $image->getSize()->getHeight(),
+            $this->newWidth,
+            $this->newHeight
+        );
+
+        // resize the image accordingly
+        return $image->resize(new Box($newWidth, $newHeight));
+    }
+
+    /**
+     * Calculates new width and height for an image by keeping the aspect ratio,
+     * not exceeding the maxWidth and maxHeight parameters
+     *
+     * @param int $width
+     * @param int $height
+     * @param int $maxWidth
+     * @param int $maxHeight
+     * @return array
+     */
+    private function calculateNewDimensions($width, $height, $maxWidth, $maxHeight)
+    {
+        $widthFactor = $maxWidth / $width;
+        $heightFactor = $maxHeight / $height;
+
+        // if one of the factors is 0, we need the other one.
+        if ($widthFactor === 0) {
+            $factor = $heightFactor;
+        } elseif ($heightFactor === 0) {
+            $factor = $widthFactor;
+        } else {
+            $factor = $widthFactor >= $heightFactor ? $heightFactor : $widthFactor;
+        }
+
+        // none of the new dimensions should be 0, so take care of that...
+        // this could happen, for example, if we scale done an image with a width of 1 px
+        $newWidth = max(array(intval($width * $factor), 1));
+        $newHeight = max(array(intval($height * $factor), 1));
+
+        return array($newWidth, $newHeight);
+    }
+}

Resources/config/imagine.xml

@@ -34,6 +34,7 @@
         <!-- Filter loaders' classes -->
 
         <parameter key="liip_imagine.filter.loader.relative_resize.class">Liip\ImagineBundle\Imagine\Filter\Loader\RelativeResizeFilterLoader</parameter>
+        <parameter key="liip_imagine.filter.loader.two_way_relative_resize.class">Liip\ImagineBundle\Imagine\Filter\Loader\TwoWayRelativeResizeFilterLoader</parameter>
         <parameter key="liip_imagine.filter.loader.resize.class">Liip\ImagineBundle\Imagine\Filter\Loader\ResizeFilterLoader</parameter>
         <parameter key="liip_imagine.filter.loader.thumbnail.class">Liip\ImagineBundle\Imagine\Filter\Loader\ThumbnailFilterLoader</parameter>
         <parameter key="liip_imagine.filter.loader.crop.class">Liip\ImagineBundle\Imagine\Filter\Loader\CropFilterLoader</parameter>
@@ -126,6 +127,10 @@
             <tag name="liip_imagine.filter.loader" loader="relative_resize" />
         </service>
 
+        <service id="liip_imagine.filter.loader.two_way_relative_resize" class="%liip_imagine.filter.loader.two_way_relative_resize.class%">
+            <tag name="liip_imagine.filter.loader" loader="two_way_relative_resize" />
+        </service>
+
         <service id="liip_imagine.filter.loader.resize" class="%liip_imagine.filter.loader.resize.class%">
             <tag name="liip_imagine.filter.loader" loader="resize" />
         </service>

Resources/doc/filters.md

@@ -47,6 +47,34 @@ liip_imagine:
                 relative_resize: { scale: 2.5 }   # Transforms 50x40 to 125x100
 ```
 
+### The `two_way_relative_resize` filter
+
+The `two_way_relative_resize` filter does the same thing `relative_resize` filter does,
+but bounds the resulting image to a given height and/or width.
+
+Given an input image sized 50x40 (width, height), consider the following
+annotated configuration examples:
+
+``` yaml
+liip_imagine:
+    filter_sets:
+        my_only_height:
+            filters:
+                two_way_relative_resize: { height: 60 } # Transforms 50x40 to 75x60
+        my_only_width:
+            filters:
+                two_way_relative_resize: { width: 32 }    # Transforms 50x40 to 32x26
+        my_width_wins:
+            filters:
+                two_way_relative_resize: { height: 60, width: 32 } # Transforms 50x40 to 32x26
+        my_height_wins:
+            filters:
+                two_way_relative_resize: { height: 60, width: 100 }   # Transforms 50x40 to 75x60
+        my_no_change:
+            filters:
+                two_way_relative_resize: { }   # Transforms 50x40 to 50x40, so actually does no transformation at all
+```
+
 ### The `crop` filter
 
 The crop filter, as the name implies, performs a crop transformation