Initial module

Block/Adminhtml/About.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Block\Adminhtml;
+
+use Magento\Framework\Data\Form\Element\AbstractElement;
+
+class About extends \Magento\Backend\Block\AbstractBlock implements
+    \Magento\Framework\Data\Form\Element\Renderer\RendererInterface
+{
+    /**
+     * @var \Apptrian\ImageOptimizer\Helper\Data
+     */
+    public $helper;
+    
+    /**
+     * Constructor
+     *
+     * @param \Apptrian\ImageOptimizer\Helper\Data $helper
+     */
+    public function __construct(\Apptrian\ImageOptimizer\Helper\Data $helper)
+    {
+        $this->helper = $helper;
+    }
+    
+    /**
+     * Retrieve element HTML markup.
+     *
+     * @param \Magento\Framework\Data\Form\Element\AbstractElement $element
+     * @return string
+     */
+    public function render(AbstractElement $element)
+    {
+        $element  = null;
+        $version  = $this->helper->getExtensionVersion();
+        $logopath = 'https://www.apptrian.com/media/apptrian.gif';
+        $html     = <<<HTML
+<div style="background: url('$logopath') no-repeat scroll 15px 15px #f8f8f8; 
+border:1px solid #ccc; min-height:100px; margin:5px 0; 
+padding:15px 15px 15px 140px;">
+<p>
+<strong>Apptrian Image Optimizer Extension v$version</strong><br /><br />
+Optimize your images, reduce their file size without losing image quality and 
+speed up your site.
+</p>
+</div>
+HTML;
+        return $html;
+    }
+}

Block/Adminhtml/Button/Clear.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Block\Adminhtml\Button;
+
+use Magento\Framework\Data\Form\Element\AbstractElement;
+
+class Clear extends \Magento\Config\Block\System\Config\Form\Field
+{
+    /**
+     * Retrieve element HTML markup
+     *
+     * @param \Magento\Framework\Data\Form\Element\AbstractElement $element
+     * @return string
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function _getElementHtml(AbstractElement $element)
+    {
+        $element = null;
+        
+        /** @var \Magento\Backend\Block\Widget\Button $buttonBlock  */
+        $buttonBlock = $this->getForm()->getLayout()
+            ->createBlock('Magento\Backend\Block\Widget\Button');
+       
+        $url = $this->getUrl("apptrian_imageoptimizer/optimizer/clear");
+        
+        $confirmText = __('Are you sure you want to do this?');
+        
+        $data = [
+            'class'   => 'apptrian-imageoptimizer-admin-button-clear',
+            'label'   => __('Clear Index'),
+            'onclick' => "confirmSetLocation('".$confirmText."', '".$url."')",
+        ];
+        
+        $html = $buttonBlock->setData($data)->toHtml();
+        
+        return $html;
+    }
+}

Block/Adminhtml/Button/Optimize.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Block\Adminhtml\Button;
+
+use Magento\Framework\Data\Form\Element\AbstractElement;
+
+class Optimize extends \Magento\Config\Block\System\Config\Form\Field
+{
+    /**
+     * Retrieve element HTML markup
+     *
+     * @param \Magento\Framework\Data\Form\Element\AbstractElement $element
+     * @return string
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function _getElementHtml(AbstractElement $element)
+    {
+        $element = null;
+        
+        /** @var \Magento\Backend\Block\Widget\Button $buttonBlock  */
+        $buttonBlock = $this->getForm()->getLayout()
+            ->createBlock('Magento\Backend\Block\Widget\Button');
+       
+        $url = $this->getUrl("apptrian_imageoptimizer/optimizer/optimize");
+            
+        $data = [
+            'class'   => 'apptrian-imageoptimizer-admin-button-optimize',
+            'label'   => __('Start Optimization Process'),
+            'onclick' => "setLocation('" . $url . "')",
+        ];
+        
+        $html = $buttonBlock->setData($data)->toHtml();
+        
+        return $html;
+    }
+}

Block/Adminhtml/Button/Scan.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Block\Adminhtml\Button;
+
+use Magento\Framework\Data\Form\Element\AbstractElement;
+
+class Scan extends \Magento\Config\Block\System\Config\Form\Field
+{
+    /**
+     * Retrieve element HTML markup
+     *
+     * @param \Magento\Framework\Data\Form\Element\AbstractElement $element
+     * @return string
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function _getElementHtml(AbstractElement $element)
+    {
+        $element = null;
+        
+        /** @var \Magento\Backend\Block\Widget\Button $buttonBlock  */
+        $buttonBlock = $this->getForm()->getLayout()
+            ->createBlock('Magento\Backend\Block\Widget\Button');
+       
+        $url = $this->getUrl("apptrian_imageoptimizer/optimizer/scan");
+            
+        $data = [
+            'class'   => 'apptrian-imageoptimizer-admin-button-scan',
+            'label'   => __('Start Scan and Reindex Process'),
+            'onclick' => "setLocation('" . $url . "')",
+        ];
+        
+        $html = $buttonBlock->setData($data)->toHtml();
+        
+        return $html;
+    }
+}

Block/Adminhtml/Stats.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Block\Adminhtml;
+
+use Magento\Framework\Data\Form\Element\AbstractElement;
+
+class Stats extends \Magento\Config\Block\System\Config\Form\Field
+{
+    
+    /**
+     * @var \Apptrian\ImageOptimizer\Helper\Data
+     */
+    public $helper;
+    
+    /**
+     * Constructor
+     *
+     * @param \Magento\Backend\Block\Template\Context $context
+     * @param \Apptrian\ImageOptimizer\Helper\Data $helper
+     */
+    public function __construct(
+        \Magento\Backend\Block\Template\Context $context,
+        \Apptrian\ImageOptimizer\Helper\Data $helper
+    ) {
+        $this->helper = $helper;
+        parent::__construct($context);
+    }
+    
+    /**
+     * Retrieve element HTML markup.
+     *
+     * @param \Magento\Framework\Data\Form\Element\AbstractElement $element
+     * @return string
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function _getElementHtml(AbstractElement $element)
+    {
+        $element = null;
+        
+        $r         = [];
+        $indexed   = 0;
+        $optimized = 0;
+        
+        try {
+            $r = $this->helper->getFileCount();
+            $indexed   = $r['indexed'];
+            $optimized = $r['optimized'];
+        } catch (\Exception $e) {
+            $message = $e->getMessage();
+            return '<div class="apptrian-imageoptimizer-bar-wrapper">
+            <div class="apptrian-imageoptimizer-bar-outer">
+            <div class="apptrian-imageoptimizer-bar-inner" style="width: 0;">
+            </div><div class="apptrian-imageoptimizer-bar-text">
+            <span style="color: #f00;">' . $message . '</span></div>
+            </div></div>';
+        }
+        
+        // Fix for division by zero possibility
+        if ($indexed == 0) {
+            $percent = 0;
+        } else {
+            $percent = round((100 * $optimized) / $indexed, 2);
+        }
+        
+        $html = '<div class="apptrian-imageoptimizer-bar-wrapper">
+        <div class="apptrian-imageoptimizer-bar-outer">
+        <div class="apptrian-imageoptimizer-bar-inner" style="width:'
+        . $percent .'%;"></div>
+        <div class="apptrian-imageoptimizer-bar-text"><span>' . $percent
+        . '% ' . sprintf(__('(%s of %s files)'), $optimized, $indexed)
+        . '</span></div>
+        </div></div>';
+        
+        return $html;
+    }
+}

Controller/Adminhtml/Optimizer/Clear.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+
+namespace Apptrian\ImageOptimizer\Controller\Adminhtml\Optimizer;
+
+class Clear extends \Magento\Backend\App\Action
+{
+    /**
+     * @var \Apptrian\ImageOptimizer\Helper\Data
+     */
+    public $dataHelper;
+    
+    /**
+     * Constructor
+     *
+     * @param \Magento\Backend\App\Action\Context $context
+     * @param \Apptrian\ImageOptimizer\Helper\Data $dataHelper
+     */
+    public function __construct(
+        \Magento\Backend\App\Action\Context $context,
+        \Apptrian\ImageOptimizer\Helper\Data $dataHelper
+    ) {
+        $this->dataHelper = $dataHelper;
+    
+        parent::__construct($context);
+    }
+    
+    /**
+     * Clear index action.
+     *
+     * @return \Magento\Backend\Model\View\Result\Redirect
+     */
+    public function execute()
+    {
+        set_time_limit(18000);
+        
+        try {
+            $this->dataHelper->clearIndex();
+            
+            $this->messageManager->addSuccess(
+                __('Clear index operation completed successfully.')
+            );
+        } catch (\Exception $e) {
+            $message = __('Clear index operation failed.');
+            $this->messageManager->addError($message);
+            $this->messageManager->addError($e->getMessage());
+        }
+        
+        /** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
+        $resultRedirect = $this->resultRedirectFactory->create();
+        
+        return $resultRedirect->setPath(
+            'adminhtml/system_config/edit',
+            ['section' => 'apptrian_imageoptimizer']
+        );
+    }
+}

Controller/Adminhtml/Optimizer/Optimize.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+
+namespace Apptrian\ImageOptimizer\Controller\Adminhtml\Optimizer;
+
+class Optimize extends \Magento\Backend\App\Action
+{
+    /**
+     * @var \Apptrian\ImageOptimizer\Helper\Data
+     */
+    public $dataHelper;
+    
+    /**
+     * Constructor
+     *
+     * @param \Magento\Backend\App\Action\Context $context
+     * @param \Apptrian\ImageOptimizer\Helper\Data $dataHelper
+     */
+    public function __construct(
+        \Magento\Backend\App\Action\Context $context,
+        \Apptrian\ImageOptimizer\Helper\Data $dataHelper
+    ) {
+        $this->dataHelper = $dataHelper;
+        
+        parent::__construct($context);
+    }
+    
+    /**
+     * Optimize action.
+     *
+     * @return \Magento\Backend\Model\View\Result\Redirect
+     */
+    public function execute()
+    {
+        set_time_limit(18000);
+        
+        if ($this->dataHelper->isExecFunctionEnabled()) {
+            try {
+                $this->dataHelper->optimize();
+                
+                $this->messageManager->addSuccess(
+                    __('Optimization operations completed successfully.')
+                );
+            } catch (\Exception $e) {
+                $message = __('Optimization failed.');
+                $this->messageManager->addError($message);
+                $this->messageManager->addError($e->getMessage());
+            }
+        } else {
+            $message = __(
+                'Optimization failed because PHP exec() function is disabled.'
+            );
+            $this->messageManager->addError($message);
+        }
+        
+        /** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
+        $resultRedirect = $this->resultRedirectFactory->create();
+        
+        return $resultRedirect->setPath(
+            'adminhtml/system_config/edit',
+            ['section' => 'apptrian_imageoptimizer']
+        );
+    }
+}

Controller/Adminhtml/Optimizer/Scan.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+
+namespace Apptrian\ImageOptimizer\Controller\Adminhtml\Optimizer;
+
+class Scan extends \Magento\Backend\App\Action
+{
+    /**
+     * @var \Apptrian\ImageOptimizer\Helper\Data
+     */
+    public $dataHelper;
+    
+    /**
+     * Constructor
+     *
+     * @param \Magento\Backend\App\Action\Context $context
+     * @param \Apptrian\ImageOptimizer\Helper\Data $dataHelper
+     */
+    public function __construct(
+        \Magento\Backend\App\Action\Context $context,
+        \Apptrian\ImageOptimizer\Helper\Data $dataHelper
+    ) {
+        $this->dataHelper = $dataHelper;
+        
+        parent::__construct($context);
+    }
+    
+    /**
+     * Scan and reindex action.
+     *
+     * @return \Magento\Backend\Model\View\Result\Redirect
+     */
+    public function execute()
+    {
+        set_time_limit(18000);
+        
+        try {
+            $this->dataHelper->scanAndReindex();
+            
+            $message = $this->messageManager->addSuccess(
+                __('Scan and reindex operations completed successfully.')
+            );
+        } catch (\Exception $e) {
+            $message = __('Scanning and reindexing failed.');
+            $this->messageManager->addError($message);
+            $this->messageManager->addError($e->getMessage());
+        }
+        
+        /** @var \Magento\Backend\Model\View\Result\Redirect $resultRedirect */
+        $resultRedirect = $this->resultRedirectFactory->create();
+        
+        return $resultRedirect->setPath(
+            'adminhtml/system_config/edit',
+            ['section' => 'apptrian_imageoptimizer']
+        );
+    }
+}

Cron/Optimize.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Cron;
+
+class Optimize
+{
+    /**
+     * @var \Apptrian\ImageOptimizer\Helper\Data
+     */
+    public $helper;
+    
+    /**
+     * @var \Psr\Log\LoggerInterface
+     */
+    public $logger;
+    
+    /**
+     * Constructor
+     *
+     * @param \Apptrian\ImageOptimizer\Helper\Data $helper
+     * @param \Psr\Log\LoggerInterface $logger
+     */
+    public function __construct(
+        \Apptrian\ImageOptimizer\Helper\Data $helper,
+        \Psr\Log\LoggerInterface $logger
+    ) {
+        $this->helper = $helper;
+        $this->logger = $logger;
+    }
+    
+    /**
+     * Cron method for executing optmization process.
+     */
+    public function execute()
+    {
+        $extensionEnabled = (int) $this->helper->getConfig(
+            'apptrian_imageoptimizer/general/enabled'
+        );
+        
+        $cronJobEnabled = (int) $this->helper->getConfig(
+            'apptrian_imageoptimizer/cron/enabled_optimize'
+        );
+        
+        if ($extensionEnabled && $cronJobEnabled) {
+            $mPrefix = 'Image Optimizer Cron: Optimization process ';
+            if ($this->helper->isExecFunctionEnabled()) {
+                try {
+                    $result = $this->helper->optimize();
+                    
+                    if ($result !== true) {
+                        $this->logger->debug($mPrefix . 'failed.');
+                    }
+                } catch (\Exception $e) {
+                    $this->logger->critical($e);
+                }
+            } else {
+                $this->logger->debug(
+                    $mPrefix . 'failed because PHP exec() function is disabled.'
+                );
+            }
+        }
+    }
+}

Cron/Scan.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Cron;
+
+class Scan
+{
+    /**
+     * @var \Apptrian\ImageOptimizer\Helper\Data
+     */
+    public $helper;
+    
+    /**
+     * @var \Psr\Log\LoggerInterface
+     */
+    public $logger;
+    
+    /**
+     * Constructor
+     *
+     * @param \Apptrian\ImageOptimizer\Helper\Data $helper
+     * @param \Psr\Log\LoggerInterface $logger
+     */
+    public function __construct(
+        \Apptrian\ImageOptimizer\Helper\Data $helper,
+        \Psr\Log\LoggerInterface $logger
+    ) {
+        $this->helper = $helper;
+        $this->logger = $logger;
+    }
+    
+    /**
+     * Cron method for executing scan and reindex process.
+     */
+    public function execute()
+    {
+        $extensionEnabled = (int) $this->helper->getConfig(
+            'apptrian_imageoptimizer/general/enabled'
+        );
+        
+        $cronJobEnabled = (int) $this->helper->getConfig(
+            'apptrian_imageoptimizer/cron/enabled_scan'
+        );
+        
+        if ($extensionEnabled && $cronJobEnabled) {
+            try {
+                $result = $this->helper->scanAndReindex();
+                
+                if ($result !== true) {
+                    $mPrefix = 'Image Optimizer Cron: Scan and Reindex process';
+                    $this->logger->debug($mPrefix . ' failed.');
+                }
+            } catch (\Exception $e) {
+                $this->logger->critical($e);
+            }
+        }
+    }
+}

Model/Config/BatchSize.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Model\Config;
+
+use Magento\Framework\Exception\LocalizedException;
+
+class BatchSize extends \Magento\Framework\App\Config\Value
+{
+    /**
+     * @return $this
+     * @throws \Magento\Framework\Exception\LocalizedException
+     */
+    public function beforeSave()
+    {
+        $value     = $this->getValue();
+        $validator = \Zend_Validate::is(
+            $value,
+            'Regex',
+            ['pattern' => '/^[0-9]+$/']
+        );
+        
+        if (!$validator || $value < 1) {
+            $message = __(
+                'Please correct Batch Size: "%1".',
+                $value
+            );
+            throw new LocalizedException($message);
+        }
+        
+        return $this;
+    }
+}

Model/Config/Cron.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Model\Config;
+
+use Magento\Framework\Exception\LocalizedException;
+
+class Cron extends \Magento\Framework\App\Config\Value
+{
+    /**
+     * @return $this
+     * @throws \Magento\Framework\Exception\LocalizedException
+     */
+    public function beforeSave()
+    {
+        $value     = $this->getValue();
+        $validator = \Zend_Validate::is(
+            $value,
+            'Regex',
+            ['pattern' => '/^[0-9,\-\?\/\*\ ]+$/']
+        );
+        
+        if (!$validator) {
+            $message = __(
+                'Please correct Cron Expression: "%1".',
+                $value
+            );
+            throw new LocalizedException($message);
+        }
+        
+        return $this;
+    }
+}

Model/Config/ExactPath.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Model\Config;
+
+use Magento\Framework\Exception\LocalizedException;
+
+class ExactPath extends \Magento\Framework\App\Config\Value
+{
+    /**
+     * @return $this
+     * @throws \Magento\Framework\Exception\LocalizedException
+     */
+    public function beforeSave()
+    {
+        $value     = $this->getValue();
+        $validator = \Zend_Validate::is(
+            $value,
+            'Regex',
+            ['pattern' => '/^[\p{L}\p{N}_=,;:!&#\+\*\$\?\|\'\.\-\ \/\\\\]*$/iu']
+        );
+        
+        if (!$validator) {
+            $message = __(
+                'Please correct Utilities Path: "%1".',
+                $value
+            );
+            throw new LocalizedException($message);
+        }
+        
+        return $this;
+    }
+}

Model/Config/Options.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Model\Config;
+
+use Magento\Framework\Exception\LocalizedException;
+
+class Options extends \Magento\Framework\App\Config\Value
+{
+    /**
+     * @return $this
+     * @throws \Magento\Framework\Exception\LocalizedException
+     */
+    public function beforeSave()
+    {
+        $value     = $this->getValue();
+        $validator = \Zend_Validate::is(
+            $value,
+            'Regex',
+            ['pattern'=>'/^[\p{L}\p{N}_,;:!%&#\<\>\=\+\*\$\?\|\'\.\-\ \/]+$/iu']
+        );
+        
+        if (!$validator) {
+            $message = __(
+                'Please correct Utility Options: "%1".',
+                $value
+            );
+            throw new LocalizedException($message);
+        }
+        
+        return $this;
+    }
+}

Model/Config/Path.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Model\Config;
+
+use Magento\Framework\Exception\LocalizedException;
+
+class Path extends \Magento\Framework\App\Config\Value
+{
+    /**
+     * @return $this
+     * @throws \Magento\Framework\Exception\LocalizedException
+     */
+    public function beforeSave()
+    {
+        $value     = $this->getValue();
+        $validator = \Zend_Validate::is(
+            $value,
+            'Regex',
+            ['pattern' => '/^[\p{L}\p{N}_,;:!&#\+\*\$\?\|\'\.\-\ \/]+$/iu']
+        );
+        
+        if (!$validator) {
+            $message = __(
+                'Please correct Utilities Path: "%1".',
+                $value
+            );
+            throw new LocalizedException($message);
+        }
+        
+        return $this;
+    }
+}

Model/Config/Paths.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Model\Config;
+
+use Magento\Framework\Exception\LocalizedException;
+
+class Paths extends \Magento\Framework\App\Config\Value
+{
+    /**
+     * @return $this
+     * @throws \Magento\Framework\Exception\LocalizedException
+     */
+    public function beforeSave()
+    {
+        $value     = $this->getValue();
+        $validator = \Zend_Validate::is(
+            $value,
+            'Regex',
+            ['pattern' => '/^[\p{L}\p{N}_,;:!&#\+\*\$\?\|\'\.\-\ \/]+$/iu']
+        );
+        
+        if (!$validator) {
+            $message = __(
+                'Please correct Paths: "%1".',
+                $value
+            );
+            throw new LocalizedException($message);
+        }
+        
+        return $this;
+    }
+}

Model/Config/Permissions.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Model\Config;
+
+use Magento\Framework\Exception\LocalizedException;
+
+class Permissions extends \Magento\Framework\App\Config\Value
+{
+    /**
+     * @return $this
+     * @throws \Magento\Framework\Exception\LocalizedException
+     */
+    public function beforeSave()
+    {
+        $value     = $this->getValue();
+        $validator = \Zend_Validate::is(
+            $value,
+            'Regex',
+            ['pattern' => '/^[0-7]*$/']
+        );
+        
+        if (!$validator) {
+            $message = __(
+                'Please correct Force File Permissions: "%1".',
+                $value
+            );
+            throw new LocalizedException($message);
+        }
+        
+        return $this;
+    }
+}

Model/Config/Utility.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+namespace Apptrian\ImageOptimizer\Model\Config;
+
+use Magento\Framework\Exception\LocalizedException;
+
+class Utility extends \Magento\Framework\App\Config\Value
+{
+    /**
+     * @return $this
+     * @throws \Magento\Framework\Exception\LocalizedException
+     */
+    public function beforeSave()
+    {
+        $value     = $this->getValue();
+        $validator = \Zend_Validate::is(
+            $value,
+            'Regex',
+            ['pattern' => '/^[\p{L}\p{N}_,;:!&#\+\*\$\?\|\'\.\-\ \/]+$/iu']
+        );
+        
+        if (!$validator) {
+            $message = __(
+                'Please correct Utility field: "%1".',
+                $value
+            );
+            throw new LocalizedException($message);
+        }
+        
+        return $this;
+    }
+}

composer.json

+{
+  "name": "apptrian/image-optimizer",
+  "description": "Optimize your images, reduce their file size without losing image quality and speed up your site.",
+  "type": "magento2-module",
+  "version": "2.2.3",
+  "license": [
+    "OSL-3.0"
+  ],
+  "require": {
+    "php": "~5.5|~7.0"
+  },
+  "autoload": {
+    "files": [ "registration.php" ],
+    "psr-4": {
+      "Apptrian\\ImageOptimizer\\": ""
+    }
+  }
+}

etc/acl.xml

+<?xml version="1.0"?>
+<!--
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Acl/etc/acl.xsd">
+    <acl>
+        <resources>
+            <resource id="Magento_Backend::admin">
+                <resource id="Magento_Backend::stores">
+                    <resource id="Magento_Backend::stores_settings">
+                        <resource id="Magento_Config::config">
+                            <resource id="Apptrian_ImageOptimizer::config_system" title="Apptrian Image Optimizer" sortOrder="1" />
+                        </resource>
+                    </resource>
+                </resource>
+            </resource>
+        </resources>
+    </acl>
+</config>

etc/adminhtml/routes.xml

+<?xml version="1.0"?>
+<!--
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:App/etc/routes.xsd">
+    <router id="admin">
+        <route id="apptrian_imageoptimizer" frontName="apptrian_imageoptimizer">
+            <module name="Apptrian_ImageOptimizer" after="Magento_Backend" />
+        </route>
+    </router>
+</config>

etc/config.xml

+<?xml version="1.0"?>
+<!--
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Store:etc/config.xsd">
+    <default>
+        <apptrian_imageoptimizer>
+            <general>
+                <enabled>1</enabled>
+                <batch_size>50</batch_size>
+                <paths>pub</paths>
+            </general>
+            <cron>
+                <enabled_scan>1</enabled_scan>
+                <expression_scan>15 4 * * *</expression_scan>
+                <enabled_optimize>1</enabled_optimize>
+                <expression_optimize>0 * * * *</expression_optimize>
+            </cron>
+            <utility>
+                <use64bit>0</use64bit>
+                <log_output>0</log_output>
+                <permissions></permissions>
+                <path>bin</path>
+                <gif>gifsicle</gif>
+                <gif_path></gif_path>
+                <gif_options>-b -O3 %filepath%</gif_options>
+                <jpg>jpegtran</jpg>
+                <jpg_path></jpg_path>
+                <jpg_options>-copy none -optimize -progressive -outfile %filepath% %filepath%</jpg_options>
+                <png>optipng</png>
+                <png_path></png_path>
+                <png_options>-o7 -quiet -strip all %filepath%</png_options>
+            </utility>
+        </apptrian_imageoptimizer>
+    </default>
+</config>

etc/cron_groups.xml

+<?xml version="1.0"?>
+<!--
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Cron:etc/cron_groups.xsd">
+    <group id="apptrian_imageoptimizer">
+        <schedule_generate_every>15</schedule_generate_every>
+        <schedule_ahead_for>20</schedule_ahead_for>
+        <schedule_lifetime>15</schedule_lifetime>
+        <history_cleanup_every>10</history_cleanup_every>
+        <history_success_lifetime>60</history_success_lifetime>
+        <history_failure_lifetime>600</history_failure_lifetime>
+        <use_separate_process>0</use_separate_process>
+    </group>
+</config>

etc/crontab.xml

+<?xml version="1.0"?>
+<!--
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Cron:etc/crontab.xsd">
+    <group id="apptrian_imageoptimizer">
+        <job name="apptrian_imageoptimizer_scan" instance="Apptrian\ImageOptimizer\Cron\Scan" method="execute">
+            <config_path>apptrian_imageoptimizer/cron/expression_scan</config_path>
+        </job>
+        <job name="apptrian_imageoptimizer_optimize" instance="Apptrian\ImageOptimizer\Cron\Optimize" method="execute">
+            <config_path>apptrian_imageoptimizer/cron/expression_optimize</config_path>
+        </job>
+    </group>
+</config>

etc/module.xml

+<?xml version="1.0"?>
+<!--
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
+    <module name="Apptrian_ImageOptimizer" setup_version="2.2.3"/>
+</config>

registration.php

+<?php
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+use \Magento\Framework\Component\ComponentRegistrar;
+
+ComponentRegistrar::register(
+    ComponentRegistrar::MODULE,
+    'Apptrian_ImageOptimizer',
+    __DIR__
+);

view/adminhtml/layout/adminhtml_system_config_edit.xml

+<?xml version="1.0"?>
+<!--
+/**
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+-->
+<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
+    <head>
+        <css src="Apptrian_ImageOptimizer::css/apptrian_imageoptimizer.css" media="all"/>
+    </head>
+</page>

view/adminhtml/web/css/apptrian_imageoptimizer.css

+/*!
+ * @category  Apptrian
+ * @package   Apptrian_ImageOptimizer
+ * @author    Apptrian
+ * @copyright Copyright (c) Apptrian (http://www.apptrian.com)
+ * @license   http://opensource.org/licenses/osl-3.0.php  Open Software License
+ */
+ 
+.apptrian-imageoptimizer-bar-wrapper {
+    display: inline-block;
+    width: 98%;
+    margin: .4em .4em -0.7em 0;
+}
+
+.apptrian-imageoptimizer-bar-outer {
+    position: relative;
+    background: #eee;
+    height: 2em;
+    border: 1px solid #adadad;
+    border-radius: 4px;
+}
+
+.apptrian-imageoptimizer-bar-inner {
+    height: 2em;
+    border-radius: 4px;
+    background: rgb(210,255,82);
+    background: -moz-linear-gradient(top, rgba(210,255,82,1) 0%, rgba(145,232,66,1) 100%);
+    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,rgba(210,255,82,1)), color-stop(100%,rgba(145,232,66,1)));
+    background: -webkit-linear-gradient(top, rgba(210,255,82,1) 0%,rgba(145,232,66,1) 100%);
+    background: -o-linear-gradient(top, rgba(210,255,82,1) 0%,rgba(145,232,66,1) 100%);
+    background: -ms-linear-gradient(top, rgba(210,255,82,1) 0%,rgba(145,232,66,1) 100%);
+    background: linear-gradient(to bottom, rgba(210,255,82,1) 0%,rgba(145,232,66,1) 100%);
+    filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#d2ff52', endColorstr='#91e842',GradientType=0 );
+}
+
+.apptrian-imageoptimizer-bar-text {
+    position: absolute;
+    top: 0;
+    left: 0;
+    height: 2em;
+    width: 100%;
+    text-align: center;
+}
+
+.apptrian-imageoptimizer-bar-text span {
+    line-height: 2em;
+    vertical-align: middle;
+}
+
+.accordion .config .value.with-tooltip {
+  font-size: 1em;
+}