## How to Efficiently Fetch Images from URLs with Dimension Thresholds?

Fetching Images from URLs with Width and Height Thresholds Efficiently

Problem:

Retrieving images from a given URL that meet specific width and height requirements, such as images with both dimensions greater than or equal to 200 pixels, is a common task in web development. However, this process can be time-consuming using traditional methods.

Current Approach:

The provided code iterates through all the elements on the given URL, retrieving the image dimensions using getimagesize(). While this approach works, its execution time can be noticeable.

Proposed Solution:

To speed up the process, consider these optimizations:

• Parallel Image Download: Utilize the curl_multi_init function to download images concurrently. This technique reduces overall fetch time by initiating multiple requests simultaneously.
• Local File Storage: Instead of running getimagesize() directly on the images from HTTP URLs, download them locally and store them in a temporary folder. This avoids the overhead of HTTP requests for dimension retrieval.

Code Implementation:

The following code presents a more efficient implementation that incorporates these optimizations:

<code class="php">require 'simple_html_dom.php';
$url = 'http://www.huffingtonpost.com';
$html = file_get_html($url);
$nodes = array();
$start = microtime();
$res = array();

if ($html->find('img')) {
    foreach ($html->find('img') as $element) {
        if (startsWith($element->src, "/")) {
            $element->src = $url . $element->src;
        }
        if (!startsWith($element->src, "http")) {
            $element->src = $url . "/" . $element->src;
        }
        $nodes[] = $element->src;
    }
}

echo "<pre class="brush:php;toolbar:false">";
print_r(imageDownload($nodes, 200, 200));
echo "<h1>", microtime() - $start, "</h1>";

function imageDownload($nodes, $maxHeight = 0, $maxWidth = 0) {
    $mh = curl_multi_init();
    $curl_array = array();
    foreach ($nodes as $i => $url) {
        $curl_array[$i] = curl_init($url);
        curl_setopt($curl_array[$i], CURLOPT_RETURNTRANSFER, true);
        curl_setopt($curl_array[$i], CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.2) Gecko/20090729 Firefox/3.5.2 (.NET CLR 3.5.30729)');
        curl_setopt($curl_array[$i], CURLOPT_CONNECTTIMEOUT, 5);
        curl_setopt($curl_array[$i], CURLOPT_TIMEOUT, 15);
        curl_multi_add_handle($mh, $curl_array[$i]);
    }
    $running = NULL;
    do {
        usleep(10000);
        curl_multi_exec($mh, $running);
    } while ($running > 0);

    $res = array();
    foreach ($nodes as $i => $url) {
        $curlErrorCode = curl_errno($curl_array[$i]);

        if ($curlErrorCode === 0) {
            $info = curl_getinfo($curl_array[$i]);
            $ext = getExtention($info['content_type']);
            if ($info['content_type'] !== null) {
                $temp = "temp/img" . md5(mt_rand()) . $ext;
                touch($temp);
                $imageContent = curl_multi_getcontent($curl_array[$i]);
                file_put_contents($temp, $imageContent);
                if ($maxHeight == 0 || $maxWidth == 0) {
                    $res[] = $temp;
                } else {
                    $size = getimagesize($temp);
                    if ($size[1] >= $maxHeight && $size[0] >= $maxWidth) {
                        $res[] = $temp;
                    } else {
                        unlink($temp);
                    }
                }
            }
        }
        curl_multi_remove_handle($mh, $curl_array[$i]);
        curl_close($curl_array[$i]);

    }

    curl_multi_close($mh);
    return $res;
}

function getExtention($type) {
    $type = strtolower($type);
    switch ($type) {
        case "image/gif":
            return ".gif";
            break;
        case "image/png":
            return ".png";
            break;

        case "image/jpeg":
            return ".jpg";
            break;

        default:
            return ".img";
            break;
    }
}

function startsWith($str, $prefix) {
    $temp = substr($str, 0, strlen($prefix));
    $temp = strtolower($temp);
    $prefix = strtolower($prefix);
    return ($temp == $prefix);
}</code>

Benefits:

• The optimized code reduces fetch time significantly compared to the original approach.
• It utilizes parallel downloading using curl_multi_init, improving efficiency.
• The local file storage strategy saves time by avoiding repeated HTTP requests for dimension retrieval.

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