Resizing Images

In order to use images with custom dimensions, you can use a built-in Magento re-sizer function to generate image URLs with the correct dimensions and you will need to amend the product model.

Start by reading how to extend Nosto module and how to alter Nosto product data.

Note: In case you want a square image, only the first parameter is required.

File app/code/local/My/Nosto/Model/Meta/Product.php

<?php

/**
 * Overridden product meta data model.
 * This model is used as the data source when generating the tagging elements
 * on the product page, and when making server-to-server API calls to Nosto.
 */
class My_Nosto_Model_Meta_Product extends Nosto_Tagging_Model_Meta_Product
{
    /**
     * @inheritdoc
     */
    public function loadData(Mage_Catalog_Model_Product $product, Mage_Core_Model_Store $store = null)
    {
        parent::loadData($product, $store);

        $height = 300; 
        $width = 200;

        $image = (string)Mage::helper('catalog/image')
            ->init($product, 'thumbnail')
            ->resize($height, $width);

        $this->setImageUrl($image);

        return true;
    }
}