How to create image thumbnails of an existing image within the folder?

Question

I’m learning to program, including learning VERY MUCH with the help of you who teach me practically everything about functions and my problem now is this: I need to create thumbnails of several width and height to suit each area of the site that has different image formats according to the page viewed.

How to develop a function com PHP which enters the folder of images and make copies of these images in the desired sizes type 620x400, 310x200, 155x100?

Answer 1

First keep in mind that image manipulation using PHP (or any other platform/language) usually consumes a lot of memory depending on the image, and may even cause an error similar to this:

Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 13056 bytes) in thumbnail.php on line 36

This is virtually impossible to solve, you can even mitigate by using php.ini the memory_limit, but this is not the solution (in my opinion), because it still affects the server, even more in your case it will probably be several images at the same time.

You can rather try using a script like this (rename the file to resize.php):

<?php
function imageResize($path, $new_width, $new_height, $outputFolder)
{
    $mime = detectMimeType($path);

    switch ($mime) {
        case 'image/jpeg':
            $resource = imagecreatefromjpeg($path);
        break;
        case 'image/gif':
            $resource = imagecreatefrompng($path);
        break;
        case 'image/png':
            $resource = imagecreatefromgif($path);
        break;
        default:
            return false;
    }

    $filename = preg_replace('#\.[a-z]+$#i', '', basename($path));

    $width  = imagesx($resource);
    $height = imagesy($resource);

    if ($new_width >= $width && $new_height >= $height) {
        return false;
    }

    if ($width > $height) {
        $percentage = $width / $new_width;
    } else {
        $percentage = $height / $new_height;
    }

    $new_width  = round($width  * $percentage);
    $new_height = round($height * $percentage);

    $newImage = imagecreatetruecolor($new_width, $new_height);
    imagecopyresampled($newImage, $resource, 0, 0, 0, 0, $new_width, $new_height, $width, $height);

    $resource = NULL;

    $filename .= '[' . $new_width . 'x' . $new_height . ']';

    switch ($mime) {
        case 'image/jpeg':
            imagejpeg($newImage, $outputFolder . '/' . $filename . '.jpg', 100);
        break;
        case 'image/gif':
            imagegif($newImage, $outputFolder . '/' . $filename . '.gif');
        break;
        default:
            imagepng($newImage, $outputFolder . '/' . $filename . '.png');
    }

    $newImage = NULL;
}

function detectMimeType($file)
{
    $mime = '';
    if (function_exists('finfo_open')) {
        $finfo = finfo_open(FILEINFO_MIME_TYPE);
        $mime  = finfo_file($finfo, $file);
        finfo_close($finfo);
    } else if (function_exists('mime_content_type')) {
        $mime = mime_content_type($file);
    }

    return $mime;
}

The use would look something like:

<?php
include 'resize.php';

$pastaDestino = 'redimensionadas/';
$arquivos = 'originais/';

//Pega todas imagens
$lista = glob($arquivos . '/*.{jpg,jpeg,png,gif,JPG,JPEG,PNG,GIF}', GLOB_BRACE);

foreach ($lista as $file) {
     //Se o arquivo se chamar foto.jpg gera um arquivo com o nome "foto[155x100].jpg"
     imageResize($file, 155, 100, $pastaDestino);

     //Gera um arquivo com o nome "foto[310x200].jpg"
     imageResize($file, 310, 200, $pastaDestino);

     //Gera um arquivo com o nome "foto[620x400].jpg"
     imageResize($file, 620, 400, $pastaDestino);
}

However as I said this can generate a high memory consumption which can affect a little the server (if the script is used many times) and depending on the size of the image may occur the error already mentioned Allowed memory size.

What I recommend is to try using Javascript in front-end and upload using ajax, see a functional example here in another reply of mine:

• Memory usage PHP images

The only difference is that instead of using <input type=file> you should do so:

<?php
$arquivos = 'originais/';

//Pega todas imagens
$lista = glob($arquivos . '/*.{jpg,jpeg,png,gif,JPG,JPEG,PNG,GIF}', GLOB_BRACE);
?>

<script>
<?php foreach ($lista as $file): ?>
<?php
    $filename = preg_replace('#\.[a-z]+$#i', '', basename($path));
?>
    var pathfile = "<?php echo $file; ?>";
    var filename = "<?php echo $filename; ?>";

    //155x100
    compressImage(pathfile, 155, 100, "jpeg", function(resource) {
        uploadAjax(resource, filename . '[155x100].jpg', function(response) {
            if (response === "OK") {
                alert("sucesso");
            } else {
                alert("Ajax: " + response);
            }
        }, function(errStatus) {
            alert("erro: " + errStatus);
        });
    });

    //310x200
    compressImage(pathfile, 310, 200, "jpeg", function(resource) {
        uploadAjax(resource, filename . '[310x200].jpg', function(response) {
            if (response === "OK") {
                alert("sucesso");
            } else {
                alert("Ajax: " + response);
            }
        }, function(errStatus) {
            alert("erro: " + errStatus);
        });
    });

    //620x400
    compressImage(pathfile, 620, 400, "jpeg", function(resource) {
        uploadAjax(resource, filename . '[620x400].jpg', function(response) {
            if (response === "OK") {
                alert("sucesso");
            } else {
                alert("Ajax: " + response);
            }
        }, function(errStatus) {
            alert("erro: " + errStatus);
        });
    });

<?php endforeach; ?>
</script>

Note that the pathfile or $file in the case must contain a publicly accessible path (via http).

In the archive upload.php (of the other question) change:

define('PASTA_UPLOAD', '/home/user/projeto/data');

By the desired path where the images will be saved.