Problem with anti-alias

[Gaussian]

On a white background, using the marquee tool, I draw an anti-aliased circle, fill it with a blue color (anti-aliased on) and invert the selection.

If I take a white paintbrush and go around the edges of the circle while holding the mouse button, nothing really happens.
If I go around the circle with the same paintbrush and press/let loose of the mouse button a couple of times, it will remove the anti-alias. I don't understand that. Why does it remove the anti-alias after a few strokes? It's easy to deal with this problem, if I just have to use a couple of strokes, but otherwise it can be frustrating.

I use this technique to round one corner of a square. Inside the square I position a circle marquee, invert it and go round it with a white brush (in case I have a white background)

Look at the attached picture. The lower half is done by holding the mouse button, the upper half is done by clicking a couple of times.

I hope somebody can shine a light on this problem.

http://www3.sympatico.ca/maiziev/test.jpg

[This message was edited by Gaussian on March 11, 2002 at 09:42.]

[Gaussian]

On a white background, using the marquee tool, I draw an anti-aliased circle, fill it with a blue color (anti-aliased on) and invert the selection.

If I take a white paintbrush and go around the edges of the circle while holding the mouse button, nothing really happens.
If I go around the circle with the same paintbrush and press/let loose of the mouse button a couple of times, it will remove the anti-alias. I don't understand that. Why does it remove the anti-alias after a few strokes? It's easy to deal with this problem, if I just have to use a couple of strokes, but otherwise it can be frustrating.

I use this technique to round one corner of a square. Inside the square I position a circle marquee, invert it and go round it with a white brush (in case I have a white background)

Look at the attached picture. The lower half is done by holding the mouse button, the upper half is done by clicking a couple of times.

I hope somebody can shine a light on this problem.

http://www3.sympatico.ca/maiziev/test.jpg

[This message was edited by Gaussian on March 11, 2002 at 09:42.]

[Mark (theKeeper)]

Hi Gaussian,

Sounds like a mix up in options is being used. Can't say that 100% sure though.

Can you tell me... is that example image a blow-up? Or was that the size your circle to begin with?

Your selection should definately NOT fill that jaggy looking by default.

"The lessons to be learned, are found along the path of your journey, not at your final destination. That is only where you will rest, between lessons"

[dalel]

Could you show the square and what you are doing with it?

As I understand it, you are trying to make a square with one round corner.

I guess I don't get why you are filling the circular selection with color. If you are painting over the corner, the circle doesn't need to be filled at all.

If the background is transparent or is on another layer (it should be on another layer if it's a color), why not just draw your marquee with anti-aliasing on, position it, invert the selection, and use the eraser to erase from the square what is outside the circle? This produces a nice anti-aliased corner.

That's how I did this one.

Dale

http://www.eyesitewebdesign.com/roundcorner.gif

[dalel]

I've tried to duplicate your problem on Photoshop 5.5 and 6.0. My versions don't do what you described. The anti-alias stays.


[img]/infopop/emoticons/icon_confused.gif[/img]

Dale

Why, I’m afraid I can’t explain myself, sir, because I’m not myself, you know...
- Lewis Carroll

[\"W\"]

Gaussian

"Why does it remove the anti-alias after a few strokes?"

Because essentially, an antialiased selection is inherently, but only slightly feathered to begin with. The pixels on either side of the fence are averaged. The inner and outer pixels (by one) are partially opaque about 75% and 25%, respectively. They aid in blending into whatever is behind it.

This may go a long way in understanding what is happening. When you stroke along the selection with the brush "once" as you did for the bottom of your circle, you added white to both sides,.. once. However, when you repeated, as you did over the top, it had a cumulative effect with every iteration. If you wish, soften the edge of your brush by double clicking on the nib in the brushes pallete and move the hardness slider.

Hope that wasn't too blurry to you ... kidding.

But ... I'm sure you can find a better way of doing what you need to do by following Dale's or Mark's instructions.

I was able to duplicate in 5.5, the screen grab is below.

[Gaussian]

I guess I wasn't all to clear with my explanation.
Yes Mark, this is a magnified picture and yes Dale, this is not the way to round a corner. When I said "I use this technique", I meant the technique of going around a corner with a brush (or eraser) and wasn't reffering to filling a circle. My mistake.
What you tell me "W" is also what I noticed about what is happening when I lift up my brush a couple of times.
The more I work with Photoshop, the more I notice how difficult it is the keep the smooth edges and shadings under control. With most techniques there are always books or websites that write about it; examples enough.
When it comes to keep shading and anti-alias under control, it's hard to find any artciles that go more into detail about this subject.
Must be me, I'm too much of a perfectionist sometimes and that's the reason why I want my graphics to be as clean as possible.

Anyways, thank you guys, I really appreciate your help. [img]/infopop/emoticons/icon_smile.gif[/img]

[Erik Heyninck]

Perhaps you just use a hard-edged brush?

The cleanest work is always done with vectors, but these are pure mathematics, and not visible on the monitor (and on the Net). So what you see is a "translation".

A pixel has no fixed dimensions, so when you set your monitor to say 800 pixels width, the pixels will be more visible on a 21 inch monitor than on a 15 inch one.

Photoshop can never change the size of the pixels. Therefore when you zoon in to 200%, it takes the info of every pixel and gives this to a square of four pixels (doubling it). When you zoom out to 50% it only shows half of the info, and this is the reason the image becomes blurred when you zoom out, and gets "squary" (my word) when you zoom in.

If you don't work against time, time often works for you.

[dalel]

Eric hit the nail on the head.

I was using the soft edge brush, and so could not get the sharp edges in the example.

Using the hard edge brush, I was able to make the anti-aliasing disappear, and get a much sharper jagged edge. (by clicking several times)

Use the brushes that look faded on the edges, and you should have no problem with losing the anti-aliasing.

Dale

Why, I’m afraid I can’t explain myself, sir, because I’m not myself, you know...
- Lewis Carroll

[Gaussian]

Sorry to disappoint you guys, but even with a soft brush I lose the anti-aliasing, it only takes more time.

Adobe must have had a reason for it, so I just try to cope with this situation.

Thanks again.