Magento – Magento 2 – Why is product image size & dimensions changed after upload

Set transparency to false.
You can read more about how to configure the image properties in view.xml at http://devdocs.magento.com/guides/v2.0/frontend-dev-guide/themes/theme-images.html

<transparency>false</transparency>

Managed to put together a working solution for now by overriding the magento 2 product image class

Create a new module with the standard module.xml, registration.php, composer.json as needed.

Crete etc/di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
  <preference for="Magento\Catalog\Model\Product\Image" type="Vendor\Imagecrop\Model\Product\Image" />
</config>

Create Model/Product/Image.php

<?php

namespace Vendor\Imagecrop\Model\Product;

class Image extends \Magento\Catalog\Model\Product\Image
{

  /**
   * @see \Magento\Framework\Image\Adapter\AbstractAdapter
   * @return $this
   */
  public function resize()
  {
    if (is_null($this->getWidth()) && is_null($this->getHeight())) {
      return $this;
    }
    // if given both dimensions crop to take up max of both dimensions
    if(!is_null($this->getWidth()) && !is_null($this->getHeight())){
      $new_width = $this->_width;
      $new_height = $this->_height;

      $this->getImageProcessor();

      $orig_width = $this->_processor->getOriginalWidth();
      $orig_height = $this->_processor->getOriginalHeight();

      $new_ratio = $new_width / $new_height;

      $orig_ratio = $orig_width / $orig_height;

      // if original has wider dimensions than new dimensions
      if($orig_ratio > $new_ratio){
        $temp_width = round($orig_ratio * $new_height);

        $tmp_constrain = $this->_constrainOnly;
        $this->setConstrainOnly(false);
        $this->getImageProcessor()->resize($temp_width, $new_height);
        $this->setConstrainOnly($tmp_constrain);

        $crop_amount = floor(($temp_width - $new_width) / 2);
        $crop_remainder = ($temp_width - $new_width) % 2;

        $this->_processor->crop(0, $crop_amount + $crop_remainder, $crop_amount, 0);


      // if original has taller dimensions than new dimensions
      } else {
        $temp_height = round((1 / $orig_ratio) * $new_width);

        $tmp_constrain = $this->_constrainOnly;
        $this->setConstrainOnly(false);
        $this->getImageProcessor()->resize($new_width, $temp_height);
        $this->setConstrainOnly($tmp_constrain);

        $crop_amount = floor(($temp_height - $new_height) / 2);
        $crop_remainder = ($temp_height - $new_height) % 2;

        $this->_processor->crop($crop_amount + $crop_remainder, 0, 0, $crop_amount);

      }

    } else {
      $this->getImageProcessor()->resize($this->_width, $this->_height);
    }
    return $this;
  }


}

This should change default behavious so when you have frame, aspect ratio set to false and constrain all set to true instead of resizing to the given size by stretching it will resize the shortest dimension and crop off the ends.

Still testing this code so use at own risk.