A quick code-point mention
#File: app/code/Magento/Catalog/Model/Product/Image.php
public function resize()
{
if ($this->getWidth() === null && $this->getHeight() === null) {
return $this;
}
$this->getImageProcessor()->resize($this->_width, $this->_height);
return $this;
}
This method is where Magento 2 will kick-off creation of all those resized images in the cache
folders. This is a good place to kick off debugging if you’re having trouble with the automatic image creation.
Also – make sure GD is installed 🙂