There are SaaS for that, Uploadcare offers that for free, for instance
Good deal for a small site, but if you have traffic, it gets expensive fast. $.25/GB bandwidth vs $.085/GB from Cloudfront va $.06 at a budget CDN.
Show HN: Dynamic image size generator
11–16 of 16 posts
Re: Show HN: Dynamic image size generator
#12Nice! This is definitely an important tool when creating a site traffic in images to be displayed across a variety different sized screens. Having worked on this type of project before I'll mention a few challenges you have not yet addressed.
At some scale point, your single DynamicServer server will have more resize requests than it has CPU cycles to serve. The straightforward solution will be to add more DynamicServer instances. This means that your source image directory will have to be accessible from both instances. It also duplicates your cache directory, meaning a single image size could get generated on both servers. You might solve that by having a shared image cache network directory. Another solution could be to use a hash mechanism to determine a particular backend server from the load balancing layer, so any particular image would always be generated on the same instance.
Something interesting happens when people upload an image to their newsfeed. If it's a public newsfeed, there can be a good many requests of the image within the next several seconds at upload. This means that you can get multiple cache miss requests at the same time coming into your DynamicImage server. Your PHP processes are vertically partitioned, so your server will be simultaneously generating the resize. For users with only a few friends, this is a small waste of CPU cycles, but for users with massive user bases (e.g. Britany Spears), a single upload could grind your DynamicImage server to a halt just because of simultaneous duplicated work. Varnish (and other load balancers) can solve this by collapsing multiple requests to the same resource into a single HTTP call (https://varnish-cache.org/docs/3.0/tutorial/handling_misbeha...).
Re: Show HN: Dynamic image size generator
#13I've created scripts like these as part of our home-brewed CMS system in the early 2000's. Nice and easy dos tool. Enumerate the width and height parameters and bring down the server fast. Better way to do it is to specify, or allow admins to specify, a set of named sizes and only allow these named sizes. You could also think about adding parameters to determine the crop, or force aspect ratio etc. (with the same ris…
I did both and used a .htaccess rule to look for a sharded filepath based on the hash of the image requested and parameters in the url.
So you could o a1jjajda.jpg?size=200x150 and it would check for the existence of a/l/jjajda/200x150.jpg and if it didn't exist it would create it from a/l/jjajda/original.jpg store it at the right place and serve it.
.htaccess file looks meant I didn't have to boot PHP to serve an image the second time (we where using laravel and even optimised it takes 30-40ms to come up) and in 95% of cases at all (particulary since I then wrote a shell script that trawled the paths, built a list of common sizes and named presets and requested them when the server was quiet).
It worked out pretty well actually and had the benefit of relying on extremely robust and well tested technology.
That was some hinky looking regexs though.
RewriteCond %{QUERY_STRING} ^presets=([a-zA-Z0-9_]+)?$
RewriteRule ^files/(.*)/(.*)/(.*)/(.*) files/$1/$2/$3/%1_$4? [L,QSA]
RewriteCond %{QUERY_STRING} ^options=[\[|\{]?([0-9]*x[0-9]*)[\]|\}]?$
RewriteRule ^files/(.*)/(.*)/(.*)/(.*) files/$1/$2/$3/%1_$4? [L,QSA]Re: Show HN: Dynamic image size generator
#14I've created scripts like these as part of our home-brewed CMS system in the early 2000's. Nice and easy dos tool. Enumerate the width and height parameters and bring down the server fast. Better way to do it is to specify, or allow admins to specify, a set of named sizes and only allow these named sizes. You could also think about adding parameters to determine the crop, or force aspect ratio etc. (with the same ris…
I did both and used a .htaccess rule to look for a sharded filepath based on the hash of the image requested and parameters in the url. So you could o a1jjajda.jpg?size=200x150 and it would check for the existence of a/l/jjajda/200x150.jpg and if it didn't exist it would create it from a/l/jjajda/original.jpg store it at the right place and serve it. .htaccess file looks meant I didn't have to boot PHP to serve an im…
Thats exacly how I did it, and than the creation of a new cached file was handled by a PHP script ran as the 404 errorHandler which output the image to both the browser and file system.
Still pretty dangerous stuff i.e. ?size=10000x2000000
Re: Show HN: Dynamic image size generator
#15I've created scripts like these as part of our home-brewed CMS system in the early 2000's. Nice and easy dos tool. Enumerate the width and height parameters and bring down the server fast. Better way to do it is to specify, or allow admins to specify, a set of named sizes and only allow these named sizes. You could also think about adding parameters to determine the crop, or force aspect ratio etc. (with the same ris…
I did both and used a .htaccess rule to look for a sharded filepath based on the hash of the image requested and parameters in the url. So you could o a1jjajda.jpg?size=200x150 and it would check for the existence of a/l/jjajda/200x150.jpg and if it didn't exist it would create it from a/l/jjajda/original.jpg store it at the right place and serve it. .htaccess file looks meant I didn't have to boot PHP to serve an im…
[deleted]
Re: Show HN: Dynamic image size generator
#16Earlier quoted context omitted.
I did both and used a .htaccess rule to look for a sharded filepath based on the hash of the image requested and parameters in the url. So you could o a1jjajda.jpg?size=200x150 and it would check for the existence of a/l/jjajda/200x150.jpg and if it didn't exist it would create it from a/l/jjajda/original.jpg store it at the right place and serve it. .htaccess file looks meant I didn't have to boot PHP to serve an im…
Thats exacly how I did it, and than the creation of a new cached file was handled by a PHP script ran as the 404 errorHandler which output the image to both the browser and file system. Still pretty dangerous stuff i.e. ?size=10000x2000000
Nah, I'm a cynical fucker, I had...
$x = $x > 9000 ? 9000 : $x;
$y = $y > 9000 ? 9000 : $y;
Tbh even 81MP was pushing it but I got to put the comment
// check and limit maximum image size // it's over 9000!
As someone who was around online back then how could I resist.
EDIT: Just remembered, I had to really resist the urge to change the returned image to a raised middle finger if either parameter was out of limit, not because I didn't think it was funny but because with my luck it'd be me that fat fingered it.