How Can I Resize Images in PHP Using GD?

Resizing Images with PHP

When dealing with images in PHP, you may encounter a need to resize them automatically. This article will guide you through the process, helping you add resize functionality to your image upload script.

To resize images in PHP, you can utilize either ImageMagick or GD functions. GD, being widely available on most web hosting platforms, offers a straightforward method for image manipulation.

Consider the following function for resizing an image using GD:

function resize_image($file, $w, $h, $crop=FALSE) {
    list($width, $height) = getimagesize($file);
    $r = $width / $height;
    if ($crop) {
        if ($width > $height) {
            $width = ceil($width-($width*abs($r-$w/$h)));
        } else {
            $height = ceil($height-($height*abs($r-$w/$h)));
        }
        $newwidth = $w;
        $newheight = $h;
    } else {
        if ($w/$h > $r) {
            $newwidth = $h*$r;
            $newheight = $h;
        } else {
            $newheight = $w/$r;
            $newwidth = $w;
        }
    }
    $src = imagecreatefromjpeg($file);
    $dst = imagecreatetruecolor($newwidth, $newheight);
    imagecopyresampled($dst, $src, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

    return $dst;
}

To use this function, simply invoke it as follows:

$img = resize_image(‘/path/to/some/image.jpg’, 200, 200);

Based on personal experience, GD's image resampling notably reduces file size, particularly when processing raw digital camera images.

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