Resizing base64 Images

Question

I have multiple Images - saved as Base64 Strings and now i want to resize these images to get thumbnails of them...

Best would be using Javascript (Node-Server) to resize them, but it would be possible to resize them with php, too.

Thanks in advance

Twelfth

Answer 1

I agree to the method from Jon Hanna: Do Parsing the Base64code then load it to GD Image before Resample. However to get it back as data it is not as easy as I though. On php in GAE it will need to enable output buffering by setting output_buffering = "On" in php.ini file.

Here I explain the step in detail.

This doc is taken as reference to Create Image Resource using the Parsing of Base64code: http://php.net/manual/en/function.imagecreatefromstring.php

// Create image resource from Base64code
$data64 = 'iVBORw0KGgoAAAANSUhEUgAAABwAAAASCAMAAAB/2U7WAAAABl'
        . 'BMVEUAAAD///+l2Z/dAAAASUlEQVR4XqWQUQoAIAxC2/0vXZDr'
        . 'EX4IJTRkb7lobNUStXsB0jIXIAMSsQnWlsV+wULF4Avk9fLq2r'
        . '8a5HSE35Q3eO2XP1A1wQkZSgETvDtKdQAAAABJRU5ErkJggg==';
$image = imagecreatefromstring(base64_decode($data64));

This is an image resource which can be directly put to the Resample function: http://php.net/manual/en/function.imagecopyresampled.php

// Resample
$image_p = imagecreatetruecolor($new_w, $new_h);
imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_w, $new_h, $org_w, $org_h);

The result is also an image resource. To get it as a data we need Buffering.
See how to create a base64encoded string from image resource

// Buffering
ob_start();
imagepng($image_p);
$data = ob_get_contents();
ob_end_clean();

Using doc below I set a GCS bucket on my project as a website so I can Store & Display it directly: https://cloud.google.com/storage/docs/website-configuration#tips

//Store & Display
$context = stream_context_create([
   'gs' =>[
        'acl'=> 'public-read', 
        'Content-Type' => 'image/jpeg', 
        'enable_cache' => true, 
        'enable_optimistic_cache' => true,
        'read_cache_expiry_seconds' => 300,
    ]
]);
file_put_contents("gs://mybucket/resample/image.jpeg", $data, false, $context); 
header("Location: http://mybucket/resample/image.jpeg");

Bechtel

Worth pointing out as well that imagecopyresampled() produces a much better quality than imagecopyresized() because it interpolates. – Renn

Answer 2

Your best bet is to use PHPThumb in PHP.

An alternative is to invoke ImageMagick however you prefer:

• http://coffeeshopped.com/2009/01/creating-image-thumbnails-using-php-and-imagemagick

• http://www.hacksparrow.com/node-js-image-processing-and-manipulation.html

Oxpecker

any idea how to access to them in my node.js app after resizing with php? – Twelfth

Answer 3

No idea how to do that (or well, anything) in node.js, but the PHP bit of your question is certainly possible. After parsing the Base64, load it into a GD image and then resample it.

http://php.net/manual/en/function.imagecopyresampled.php

Fernery

well i have no write-rights on my server - how could i link this thumbs to my node.js app? any idea? – Twelfth

That falls under the "No idea how to do that (or well, anything) in node.js" bit above for me, I'm afraid. Someone else might have a good idea, hopefully. – Fernery

looking for a answer for this for 2 days now... normally it would work fine with node - but in my node-app i have no write-rights, too... that sucks – Twelfth

Best of luck. I can only answer to the bit I know about. – Fernery

How are you going to do permanent storage in the future? One thing you can do as an interim solution is to have a app-level global image hashtable element that stores the images as a cache... – Genovese

this app is only for a projet at university - so it never will be needed to do permanent storage - even if i would like to - simplest solution would be spending money and getting write-rights... – Twelfth

Answer 4

Maybe you just can use a lib to handle that. Try WideImage. I have used it and worked nicely.

Example:

$image = base64_decode(preg_replace('#^data:image/\w+;base64,#i', '', $req->image));

$thumbnail = WideImage::load($image)
  ->resize(300, 300, 'inside')
  ->crop('center', 'center', 300, 300);

Library Documentation: http://wideimage.sourceforge.net/

Psychogenesis