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Thread: Anti-Aliasing with Threshold

  1. #1
    Barrista
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    Anti-Aliasing with Threshold

    Well, a couple of people know that I've been working on this, so I just wanted to share my findings to date.

    I've been looking at how Anti-Aliasing math works, specifically how an "anti-alias filter" might effect things such as adjust>threshold or level-adjusted masks. It seems that true anti-aliasing comes from infinitely complex (pure math or vector) objects. Anti-Aliasing averages the edge weight in a pixel to the background, and rasterizes the result. What you get is the appearance of a smooth line.

    Coming from a threshold or bitmap, right now I can't see (without vectorizing the edge) how an anti-alias filter would function. With 1-bit data, there could be no present data in the background space. The pixel is on, or it's off. So you'd have to average the edge through some sort of sketch filter or vectorization tool, and of course, that's inpercise. And clumsy and/or time-consuming.

    The fractal guys have come up with an interesting solution though. A lot of the freeware fractal generators won't anti-alias either, so their method of anti-aliasing is actually rendering their fractals at four times (or more) their intended output size and reducing them in Photoshop to 25%. The necessary information between background and foreground becomes available with the additional pixel information. Obviously, the greater the increase/decrease, the more percise the edge anti-alias will be...

    Thought I'd share... the only way I can see of making a true "anti-aliasing threshold filter" is by recreating the threshold filter but adding anti-alias functionality. For those of you interested in trying out the fractal method though, the information is available to you. For me, the job has gotten a little more difficult...



    Any input or insight you guys have would be cool...

    [Edited on 18-12-2003 by Phil_The_Rodent]

  2. #2
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    Phil,


    I hope you don't take this the wrong way. Just trying to be somewhat funny. Do you have anything else to do besides photoshop? *lol* As I'm reading this, I'm like thinking "Dang, does he eat, sleep, and drink photoshop". Even though, I understand some things that you are saying, I truly don't have the expertise to know about everything you are saying because to me it looks mumble jumble to me. *lol*


    TRexSmarts

  3. #3
    markLearst
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    We can thank the fine folks over at MIT for coming up with anti-aliasing

  4. #4
    Barrista
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    Trex: My outside work life is Tracey, band, beer, and photoshop. I live, eat, breathe and sleep this stuff... I was never gifted with extraordinary abilities in art.. but I love it. I just try to learn as much as I possibly can. I firmly believe a dedicated person will outlive a "gifted" person... it just takes some time to show...

  5. #5
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    I like this quote:


    "firmly believe a dedicated person will outlive a "gifted" person... it just takes some time to show..."


    You just make that up? One of these days after I get out of graduate school in the year 2006, I hope to have time to learn more about Photoshop. So, right now, I'm learning bits and pieces that will get me by for now. I notice myself the other day doing things by using the shortcuts rather than actually going thru the mouse strokes.


    Now getting back to the Anti-aliasing, should we at every chance leave it clickedf on when creating things? Just curious because I know I have a lot of problems with jagged edges and stuff. I think one of these days I will learn to create smooth edges.


    TRexSmarts

  6. #6
    Barrista
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    Originally posted by TRexSmarts
    I like this quote:


    "firmly believe a dedicated person will outlive a "gifted" person... it just takes some time to show..."


    You just make that up? One of these days after I get out of graduate school in the year 2006, I hope to have time to learn more about Photoshop. So, right now, I'm learning bits and pieces that will get me by for now. I notice myself the other day doing things by using the shortcuts rather than actually going thru the mouse strokes.
    As a statement? Yes, just made it up. It's probably been phrased better elsehwere. As a belief? I think it was best described in Aesop's "Tortose and the Hare"...


    Now getting back to the Anti-aliasing, should we at every chance leave it clickedf on when creating things? Just curious because I know I have a lot of problems with jagged edges and stuff. I think one of these days I will learn to create smooth edges.


    TRexSmarts
    Anti-aliasing would be good for masking and web pages. For print? I don't need it for vector art or text as the printer RIPs these things to the specifications it needs. Jagged edges, yes, are causd by aliasing the majority of the time...

  7. #7
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    I know this is off topic. Sorry. Just that I'm kind of lost on when certain things are over my head. But I want to learn it though. There are times I'm amazed about how smart people are. *lol* Maybe that didn't come out right. I love it when people make me think about things like a lot of people on photoshopcafe does. Sometimes it goes to a point that I tell myself, I have a lot to learn. *lol* I think it's going to be time for me to start getting some Photoshop books and etc. Right now, all my knowledge is from internet or tutorials. Going to have to buy Colin's whole line of books.


    TRexSmarts

  8. #8
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    Sometimes it goes to a point that I tell myself, I have a lot to learn.

    Sometime I would be satsified to know what the question is.:P

    [Edited on 18-12-2003 by x5dr]

  9. #9
    Phil…

    Your comments re. acquired skills vs. natural ability reminded me of the debate that was going on the other day about education/qualifications vs. raw talent. I was sensitive to the fact that there are a lot of younger people here who haven’t yet embarked on tertiary studies, & also enthusiasts who haven’t the inclination or maybe the opportunity to pursue a career in graphics, & I just didn’t like the idea of them being alienated by people making comments along the lines that qualifications count for so much more than experience/trial & error – the inference being that their endeavours to teach themselves PS, etc are somehow not valid or important compared to the work produced by professionals on the job. I really took exception to that, which is why I was arguing that talent is what counts.

    But you’ve raised another interesting point…striving for your personal best while being fully aware of your strengths & weaknesses. I believe that people are at their strongest when they know their weaknesses, but I have to say, I disagree with you when you say you weren’t blessed with extraordinary artistic ability! I don’t know quite what you mean by this, but if you’re referring to the basic ability to paint & draw, etc…well there’s just SO much more to being creative than that! I’ve seen your work (not much, but some) & the gift of sensitivity & discernment is one of the most important elements of the creative process. You obviously have a really good eye…& that’s one of the beautiful things about digital art is that you can express yourself if you have an artistic eye, but maybe not the most creative hand!

    I remember having to write an essay at art school defining what art is - it’s an impossible question - much easier to say what art isn’t! The only conclusion I could reach with conviction was that art is the result of a creative process of decisions & considerations. Some artists never so much as lift a pencil – they get other people to carry out their wishes – from the old masters right up to modern artists like Jeff Koons…so maybe art is created more in the head than by the hand…digital art has certainly removed much of the manual element. I have to say, I like it that way…one of the reasons I prefer making things on the computer is the absence of dirty brushes, inked up plates, etc!

    Basically, the position I take is that I really have no tolerance for any kind of elitism/snobbery/closed-mindedness…no one should be excluded from giving creativity a whack, whatever their strengths & weaknesses may be or what their approach is. That’s the beauty of art/design is it’s for everyone who wants to take part…& the process is just as important as the outcome. I agree that if you arm yourself with knowledge – whether it be technical knowledge (such as the ins & outs of PS & other applications or the qualities of different media/processes) or historical knowledge (which I personally think is also really important) or just plain old experience (which usually involves lots of mistakes!) – you’ll be so much closer to reaching full potential.

    I’m not the most skilful or versatile designer/illustrator/artist (whatever you want to call it) in the world…maybe I’m a bit of a one trick pony…but I know my limitations & I push them to the max…& I think that’s what counts at the end of the day, getting to know yourself via the creative process..& enjoying it! And digital art has opened up a whole new world of potential & has made art/design so much more accessible - so I'm all for it, I LOVE it!

    I know this is completely off your original topic & I’m sorry about that. Good Lord, I can ramble on… But I just wanted to expand on what I was saying the other day because it wasn’t my intention to make it seem like I think only people with outstanding artistic talents have the right to make art.

    Phew…

  10. #10
    Barrista
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    Thanks DP.

    Back on topic, I'm also thinking this:

    If x+1 and y+1
    or x+1 and y-1
    or x-1 and y+1
    or x-1 and y-1
    equals 0 (k),
    then 128 (50% grey).

    Else, 256 (white).

    It's a single level of anti-alias. Not sure if it will work well, but I'm gonna code it probably over the weekend. The softer curves will not work out with this, but it might be okay. Maybe I'll code a second pass for softening. Hmm...

    EDIT
    A little more elegant (allows a multple pass)...

    If a pixel is white, and
    x-1 and y-1 or
    x-1 and y+1 or
    x+1 and y-1 or
    x+1 and y+1 or
    is not white,
    take those two values and average them, and devide by two.

    [Edited on 18-12-2003 by Phil_The_Rodent]

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