Re: Mixing image filters on an image
Re: Mixing image filters on an image
- Subject: Re: Mixing image filters on an image
- From: Gyongock Kim <email@hidden>
- Date: Tue, 16 Nov 2004 17:05:54 +0900
Thanks for your answer.
Actually I have no idea about the look-up tables.
You mean you make look-up tables for image filters in advance and just apply later?
Can you explain how to implement it as look-up tables for image filter?
Thank a lot.
G. Kim
2004. 11. 16, 오후 3:11, Brendan Younger 작성:
On Nov 15, 2004, at 6:45 PM, 김경옥 wrote:
Hi,
I'm implementing an image editor and wondering how to make users be able to mix the filters, such as brightness, contrast, hue, saturation and so on independently.
Because if I apply brightness and contrast on an image and undo brightness adjustment, I need to apply contrast only on the original image again.
So I always check every value for brightness, contrast, hue and so on, and apply all the filter on the original image sequentially every time any value of the adjustment has changed.
Is there any way to apply the image filter independently?
<x-tad-bigger>Any help would be greatly appreciated.</x-tad-bigger>
Cocoa-dev isn't really the best place to ask these sorts of questions. Certain filters are effectively "undoable" but layering them in between different filters means that you'll have to do a lot of bookkeeping to keep track of the interdependencies. If all you're doing are things like brightness and contrast adjustment, you can very easily implement these as look-up tables. It's then trivial change the look-up table in response to an undo request. Applying a single look-up table to an image is ludicrously fast and if you notice a slow-down on it, then you're doing it wrong. Whatever you do, don't re-calculate every pixel value every time.
Also, if you can wait until Tiger (10.4) ships, you can use CoreImage to do a lot of this for you.
Brendan Younger
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