How to compress images in PHP?

Question

On my website, people can post messages and along with these messages an image (which is saved in a folder). I wonder if there is any class or any means using PHP to compress these images without losing quality.

Note: Extensions accepted: . jpg and . png

Answer 1

You can test the quality loss using the PHP GD and see if it fits, you can also do this procedure while uploading the image:

function compressImage($source_path, $destination_path, $quality) {
    $info = getimagesize($source_path);

    if ($info['mime'] == 'image/jpeg') {
        $image = imagecreatefromjpeg($source_path);
    } elseif ($info['mime'] == 'image/png') {
        $image = imagecreatefrompng($source_path);
    }

    imagejpeg($image, $destination_path, $quality);

    return $destination_path;
}

Explaining the functions used:

• getimagesize(): returns image information (type, size, dimensions, etc.), we use to get the original image MIME Type.
• imagecreatefromjpeg(): creates a new image from the original image.
• imagejpeg(): sends an image to the browser or to a file, this is where the lightest image is created.

Finally the function returns the path of the lightest image.

Example of use: $img = compressImage("images/praia.jpg", "images/compressed/compressed_praia.jpg", 6);

Answer 2

There are several image processing libraries, some I know are:

• GD2
• Imagemagick

I advise you to use the Imagemagick (that is why).

Some things you can do to let your images get smaller and smaller.

• Convert image to JPG
• Use a quality between 80 and 90 for JPG
• Resize the image for a maximum size. Ex.: 800px wide
• Delete the EXIF headers

Sources:

http://php.net/manual/en/book.imagick.php

Example:

<?php
    $image = new Imagick();

    $image->thumbnailImage(800, 300);
    $image->readImage('image.jpg');
    $image->setImageFormat('jpeg');
    $image->setImageCompressionQuality(85);
    $image->stripImage();

    $image->writeImage('nova_imagem.jpg');

?>