Why

Don't browsers do at least bilinear scaling these days?  It can't be that CPU intensive.

Update: Turns out, it is pretty CPU intensive.

Resizing a 750x1200 image to 500x800 to suit my blog takes 2ms using nearest-neighbour scaling (which is what browsers use), 49ms using bilinear filtering, and 117ms using bicubic filtering.

The time is proportional to the number of pixels in the target image; starting with a 1500x2400 image took only 1 or 2% longer.

So not great for automated image sizing - not without a healthy cache, anyway - but pretty good for generating thumbnails on the fly.  A 150x240 thumbnail takes 4.5ms to generate; at 200x320, about 8ms.

One thing I will likely use this for is avatars.  I don't want to enforce a fixed size for avatars across mu.nu/mee.nu, because the idea has always been that it's your [blog|forum|wiki|whatever] and you control the way it looks.  But having avatars of all different sizes looks like crap, and having a range of sizes (which is what I was considering) is fiddly.

But if I make it so that you upload one image at say 240x240, and that automatically gets resized according to the template tag, that could work well.  Some timings on that: 50x50 0.3ms; 60x60 0.4ms; 75x75 0.7ms; 100x100 1.2ms.  It takes a minimum of 3-5ms to serve a file in the first place, so that's not a huge imposition on the server.

[comment.avatar size=60] here we come!

Posted by: Pixy Misa at 08:03 PM | Comments (4) | Add Comment | Trackbacks (Suck)
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