I want to be able to generate image thumbnails without saving them to the server. So far, I've come up with this code, but I'm not sure what to do with $code.
$code = system("convert galleries/13_0.jpg -resize 400x270 /dev/stdout");
How would I go about plugging $code into the PHP/HTML to get the raw image code to display as a jpg?
I would advise you not to do this from the system as you have described.
PHP has libraries for doing this sort of thing.
http://www.php.net/manual/en/ref.image.php. http://php.net/manual/en/book.imagick.php.
And there are libraries the wrap these native functions for manipulating images. https://imagine.readthedocs.org/en/latest/
That way all your code is in PHP and you are not relying on the system to do anything (providing PHP has been compiled with the libraries as described. They are standard libraries available in most PHP builds and you can enable them if they are not included).
Edit: I'm advocating that you.
with imagine you would do it thus:
$imagine = new Imagine\Gd\Imagine();
$size = new Imagine\Image\Box(400, 270);
$imagine->open('/path/to/large_image.jpg')
->resize($size)
->show('jpg');
If the $code is the raw data, could you have another file getimage.php which would write the data out but set the header content type to image/JPEG? So your img src would be getimage.php?image=13_0.jpg for example?
I would save it to memory, then read it, then delete it. /dev/shm is a ramdrive on most Linux systems.
$tmp = '/dev/shm/'.uniqid('',true).'.jpg';
system("convert galleries/13_0.jpg -resize 400x270 $tmp");
header("Content-Type: image/jpeg");
header('Content-Length: '.filesize($tmp));
readfile($tmp);
unlink($tmp);
