Image Manager

Introduction

ImageManager is a small Util class for images held in memory as base64 text, for example a picture drawn on a canvas, taken with the camera in the browser, or sent in a JSON body. It can tell you an image's type and width, and resize it. It does not read or save files.

Get an instance with Util::ImageManager():

$images = Util::ImageManager();
$type = $images->imageInfo($base64); // "png"

All methods take the raw base64 data, without the data:image/png;base64, prefix that a browser data URL starts with. Remove the prefix first. With it, the data does not decode to an image and the methods return false.

The methods use the PHP gd extension.

Image Manager or File Manager?

File Manager also handles images. The two don't overlap much:

	Image Manager	File Manager
Input	Base64 text in memory	An uploaded file, or a file on disk or in S3
Resizing	reSize(): to one width, height follows	createImageThumbnail(): several sizes at once, each fitted inside a width and height
Output format	Always JPEG	Same format as the original
Saves files	No	Yes, locally or in S3

Use File Manager for images uploaded from a form: imageUploadv2() then createImageThumbnail(). Use Image Manager only when the image reaches your controller as base64 text and you want to check or shrink it before you save it.

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How to check and shrink a base64 image before saving it

A signature pad or camera component usually gives you a data URL. Strip the prefix, check the type, shrink the image if it's too wide, then save it with File Manager's base64ImagetoImageFile().

private function save_photo()
{
    $res = new Response();
    $data = $this->getRequest()->getData();

    // "data:image/png;base64,iVBORw0KGgo..."
    $dataUrl = $data['photo'] ?? '';
    $comma = strpos($dataUrl, ',');
    $base64 = $comma === false ? $dataUrl : substr($dataUrl, $comma + 1);

    $images = Util::ImageManager();

    $type = $images->imageInfo($base64);
    if (!in_array($type, array('jpeg', 'png', 'webp'), true)) {
        echo $res->create(200, 'Send a JPEG, PNG or WebP image.', false);
        return;
    }

    if ($images->checkImageSize($base64) > 1200) {
        $base64 = $images->reSize(1200, $base64);
        $type = 'jpeg'; // reSize() always returns a JPEG
    }

    if ($base64 === false) {
        echo $res->create(200, 'Could not read the image.', false);
        return;
    }

    $dir = FileManager::create_directory('myapp/photos/'); // "/storage/myapp/photos/"
    $name = uniqid() . '.' . ($type === 'jpeg' ? 'jpg' : $type);

    $saved = FileManager::base64ImagetoImageFile(
        'data:image/' . $type . ';base64,' . $base64,
        RDIR . $dir,
        $name
    );

    if (!$saved) {
        echo $res->create(200, 'Could not save the image.', false);
        return;
    }

    $res->setData(array('url' => FileManager::buildUrl($dir . $name)));
    echo $res->create(200, 'Photo saved.', true);
}

base64ImagetoImageFile() writes to the local disk only. With S3 storage, write base64_decode($base64) to a temporary file and upload it with FileManager::putObject(). See File Manager.

⚠️ reSize() always produces a JPEG. Transparent parts of a PNG, WebP or GIF turn black, and an animated GIF keeps only its first frame. Resize only images that can lose transparency, such as photos.

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How to make a fixed-width copy

reSize() scales an image to the width you give and works out the height from the aspect ratio. It also enlarges images narrower than that width, so check the width first if you only want to shrink:

$images = Util::ImageManager();

$width = $images->checkImageSize($base64);
$preview = ($width !== false && $width > 300)
    ? $images->reSize(300, $base64)
    : $base64;

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Image Manager methods

imageInfo

Description:

The imageInfo method returns the type of a base64 image, taken from its content rather than from any name or prefix.

Syntax:

$images = Util::ImageManager();
$type = $images->imageInfo($base64);

Parameters:

• $imageString: Raw base64 image data, without a data: prefix.

Return Value:

• String: The part of the MIME type after /, in lowercase: jpeg, png, gif, webp and so on. It is not the full MIME type.
• false: If the string is empty or is not an image.

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checkImageSize

Description:

The checkImageSize method returns the width of a base64 image in pixels. Despite its name, it does not check against a limit and it does not return the height.

Syntax:

$images = Util::ImageManager();
$width = $images->checkImageSize($base64);

Parameters:

• $imageString: Raw base64 image data, without a data: prefix.

Return Value:

• Integer: The width in pixels.
• false: If the string is empty or is not an image.

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reSize

Description:

The reSize method scales a base64 image to the given width, keeps the aspect ratio, and returns the result as a base64 JPEG at quality 100. It enlarges images narrower than $width.

Syntax:

$images = Util::ImageManager();
$resized = $images->reSize(500, $base64);

Parameters:

• $width: The new width in pixels. Must be a number greater than 0.
• $imageString: Raw base64 image data, without a data: prefix.

Return Value:

• String: The resized image as raw base64 JPEG data, without a data: prefix.
• false: If $width is not a positive number, the string is empty, or it is not an image. Invalid image data also logs a PHP warning.

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setImageString / getImageString

Description:

The setImageString and getImageString methods store and read a base64 string on the instance. The other methods don't use the stored value, so you must still pass the string to them.

Syntax:

$images = Util::ImageManager();
$images->setImageString($base64);
$width = $images->checkImageSize($images->getImageString());

Parameters:

• $imageString (setImageString only): The string to store.

Return Value:

• String: getImageString returns the stored string, or null if none was set. setImageString returns nothing.

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