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X.4 Core Image

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Core Image is a powerful new graphics engine that found its way into Mac OS X.4. Providing powerful compositing, being extendable by filters an utilising all the processing power it can find in your computer, it’s quite a cool beast. In my previous notes on it, I said I may be overly optimistic here, but I like it. And that’s pretty much the state I remain in until today.

While the whole Core Image technology may be cool and modern, I haven’t even seen it at its full beauty outside of Apple’s demonstrations. Just because my old Powerbook doesn’t have a graphics chip that’s even close to being able to support Core Image. Apple claim that Core Image is smart enough to scale down to older machines, using the processors it finds there to achieve the same effects at a slower speed.

Apple’s foremost graphics demo application, Quartz Composer (which comes with the Developer Tools), that all the cool demos seem to be made with won’t even launch on my computer for its lack of new graphics chip. I think that’s mostly because of the lack of 3D power, though, than because of the Core Image aspects I mentioned above. Still, I’d like to ironically note that the files saved by Quartz Composer can still be displayed by QuickTime. At glacial speeds and incompletely, I might add, so QuickTime should better not even try to do this on older computers.

Effect Stack palette of Core Image Fun House Core Image Fun House (also part of the Developer Tools), however, seems to run just fine on older computers as well. Aside from a horrendous tendency to crash frequently and it’s inability to have anything but a straight stack of layers, it should be sufficient to give you an idea of Core Image’s abilities. You can generate backgrounds and insert images. Those can be distorted or filtered. And there can even be animated transitions.

With slower computers, I recommend not using the example images supplied by Apple. They’re large enough to make your computer cry – or at least be painfully slow. Rather use a small image. Starting with a screenshot of Apple’s Core Image advertisement page and a few letters, I made the image below. To me it hints that Core Image gives you a fairly powerful set of tools. And one that can be used to create rather ugly things with very little effort.

Core Image Fun House example

Doing this kind of playing around (rather than any actual measurements), Core Image’s speed leaves a mixed impression. Standard filters on small images seem to run reasonably quickly. But once you have larger images, like an 800x800 image, even things like blurring start to feel slow and changing the brightness seems to happen at at most half the speed of GraphicConverter. This may be due to the whole image being updated at once after all the computations have been done rather than updating the display block-by-block like Photoshop does, but at the end of the day it makes my computer feel a few years older than it is.

So, for the time being, I don’t think I’ll get into Core Image too much. The only place where I can see myself using it actively is in the ever wonderful GraphicConverter which started having support for Core Image graphics filters soon after the release of X.4. GraphicCoverter’s UI for the filters isn’t exactly great or responsive yet but I’m sure that Thorsten Lemke will manage to improve that soon.

While Thorsten certainly is one of the more active and experienced Mac programmers around, GraphicCoverter has always been relatively slow to pick up new features offered by the OS. I assume that there are many reasons for that, ranging from the fact that GraphicConverter has been around for ages and still works on Mac OS 8 in its current version to the fact that Thorsten knows how to keep himself busy with gazillions of other improvements that are documented in GraphicConverter’s version history. As he was able to enhance GraphicConverter with Core Image fairly quickly (and with some Automator actions and Spotlight finding as well) suggests that both Thorsten and Apple are good at their respective jobs of programming and making the System’s new features easily available (even to ‘old-fashioned’ applications).

Initially I was tempted to go ahead and make some Core Image filters of my own. But as it turned out that I don’t really use Core Image all that much and the documentation suggests that it’d be helpful to use Quartz Composer when starting to progam the filter, there’s not too much point in doing this for me at this stage, so I can’t say a lot about that. It doesn’t look like there have been floods of cool filters coming along already, so people may be taking their time.

Apart from those basic problems, it also seemed like the capabilities of those filters are quite limited – even loops seem to be a problem. A shame… after seeing how slooow Java is on my computer with a little applet that one of the guys in our department wrote for drawing Mandelbrot and Julia sets (which lets you draw a route through the Mandelbrot set and it’ll ride along that route drawing an animation of the Julia sets at each point of the route), I had this little urge to come up with a clever and fast way to view those on my computer. A way that doesn’t involve using X11 to run the web browser on one of the Linux machines…

In short – no, I don’t have any real use for Core Image, no, I haven’t seen any compelling applications yet that make it look like a must-have. But I still hope that we will get them in the future.

June 25, 2005, 17:34

Tagged as X.4.


Comment by Sören Kuklau: User icon

My iBook is still in repair and too slow to properly handle CoreImage anyway, but have you seen LiveQuartz?


It looks like a “what Fun House should have been” application. Still in beta, and with an unfortunately kludgy UI, but the demo movie and screenshots look nice.

June 25, 2005, 18:56

Comment by ssp: User icon

Looks a bit ugly but interesting.

And it’s very slow on my computer. It won’t even draw proper lines with the brush :(

June 25, 2005, 19:34

Comment by Jacques Lema: User icon

CoreImage is very fast when it can use GPU hardware acceleration, or at least it seems according to the demos. The problem is a lot of the existing base macs just don’t have supported GPU (shader support, so called DirectX9 compatible).

I am currently developing an image manipulation app (http://www.chocoflop.co/) and one thing I noticed is Core Image tends to go much slower if you have to output a big image on a lower end graphics card. (I have an ibook with a 9200 radeon=).

I already “precalculate” the result of all filters (many layers with layer masks and live filter layers, transparency) onto a display Image Accumulator upon every change. So when you display it in the end there’s no much filter applying. But there’s an enormous difference say with a 1280x1024 image (in 128 bit floating point depth) and the same image when you zoom on a part of it. If the area you update is smaller than a certain limit the GPU seems to be able to use it better. So maybe it would be wise to use several 256 pixels textures (à la photoshop but without disk caching).

Basically to be usable on a lower-end computer (like mine) it is better to limit the number of “Live layers”. That is layers that apply filter in real-time versus layers where filters and effects are kept in a bitmap accumulator.

Also when writing a CoreImage based app it is VERY important to learn how to use threading. If repainting is slow you should not let it block the whole app. I use several threads in my app, one for rendering all layers onto the destination image and another for painting.

So basically Core Image probably sucks on lower end hardware, but hardware indepence is really great. I suggest developers work on lower end hardware (easy for me since I can’t afford more expensive machines :-) . The more powerful hardware you have the more you’ll be able to use dynamic features.

July 28, 2005, 15:39

Comment by ssp: User icon

I suggest developers work on lower end hardware

Nice one…

July 28, 2005, 23:12

Comment by Jacques Lema: User icon

Well, reading it again it might sound a bit stupid since they would probably be less productive (slower compile time …).

If you test on low-end harware but your machine is a dual g5, you’ll just check that “it works” but if it’s your machine and you don’t have another one you’ll really care more about it working well. And if you have a better machine, well It’ll just run very well.

Maybe developrs should have a g5 at work and a mac mini or ibook at home so they could experience both sides in their daily life.

Huh, anyone willing to donate a Dual G5? :-)

August 8, 2005, 12:22

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