PHP HTML image output

Question

In the PHP manual for base64_encode() I saw the following script for outputting an image.

Answer 1

Because imagepng outputs bool or image stream directly to output.
So, in order to get image data you should use output buffers like this:

ob_start();
imagepng($im);
$image = ob_get_contents();
ob_end_clean();
echo '<img src="data:image/png;base64,'.base64_encode($image).'" />';

Answer 2

Ok, sorry, I was thinking too fast :)

imagepng() will output raw data stream directly to the browser, so you must use ob_start() and other output buffering handles to obtain it.

Here you are:

ob_start();
imagepng($yourGdImageHandle);
$output = ob_get_contents();
ob_end_clean();

That is - you need to use $output variable for you base64_encode() function.

Answer 3

Most likely because the data: URI scheme is extremely limited and good to use unless there is absolutely no way around it.

In Internet Explorer, for example, this doesn't work at all until IE 8; and in there, there is a global 32 kilobyte limitation for data: URIs.

Answer 4

You have to save your image as a PNG first, and then read from it to get its contents as a value.

http://www.php.net/manual/en/function.imagepng.php

imagepng() does not return the PNG file. It outputs it directly to the browser and then returns a boolean meaning success or failure.

(from php.net:) PHP internally works with a temporary file when sending the image to the browser, so you'll gain nothing by calling imagepng() twice.