How to get image resource size in bytes with PHP and GD?

Question

I'm resizing images with php gd. The result is image resources that i want to upload to Amazon S3. It works great if i store the images on disk first but i would like to upload them directly from memory. That is possible if i just know the bytesize of the image.

Is there some way of getting the size (in bytes) of an gd image resource?

Answer 1

You could use PHP's memory i/o stream to save the image to and subsequently get the size in bytes.

What you do is:

$img = imagecreatetruecolor(100,100);
// do your processing here
// now save file to memory
imagejpeg($img, 'php://memory/temp.jpeg'); 
$size = filesize('php://memory/temp.jpeg');

Now you should know the size

I don't know of any (gd)method to get the size of an image resource.

Answer 2

I can't write on php://memory with imagepng, so I use ob_start(), ob_get_content() end ob_end_clean()

$image = imagecreatefrompng('./image.png'); //load image
// do your processing here
//...
//...
//...
ob_start(); //Turn on output buffering
imagejpeg($image); //Generate your image

$output = ob_get_contents(); // get the image as a string in a variable

ob_end_clean(); //Turn off output buffering and clean it
echo strlen($output); //size in bytes

Answer 3

This also works:

$img = imagecreatetruecolor(100,100);

// ... processing

ob_start();              // start the buffer
imagejpeg($img);         // output image to buffer
$size = ob_get_length(); // get size of buffer (in bytes)
ob_end_clean();          // trash the buffer

And now $size will have your size in bytes.