1 Pixel Bug?...Solid Fill is not 100% Solid Fill

Hello all,

I stumbled upon something that finds me vaguely recalling a mention in the past of some sort of "1 pixel" problem in Photoshop. I know even that description is vague in and of itself, so I'll just describe what I've encountered:

I created a 100x100 pixel new image with a white background, selected the right half exactly (50x100) and filled that area with solid black using the Fill Tool options set at 100% opacity and 0 tolerance. The result should have been an edge-to-edge fill of RGB = 0/0/0, yet I found the color sampling in the Info palette indicated RGB = 15/15/15 for the last 1 pixel column at the left and right edges of the black-filled area.

Moreover, if the selction marquee was still active around the filled region and I reapplied the Fill Tool, that 15/15/15 value was reduced to 1/1/1 and would only "zero out" once I applied the Fill Tool once more. However, if I first deselected the area and then filled the 15/15/15 region, it did "zero out" correctly.

This behavior was seen in both PS7 and PSCS. While I don't consider it all too significant, it nonetheless begs the question, WHY?

Does this have to do with color value errors introduced by the active marquee around a selected area?

Thanks,

Daryl

Daryl,

Is your marquee set to anti-alias?

Len,

That did the trick...thanks! I could have sworn I'd already explored whether or not aliasing affected the situation, but this was something I observed on the side while exploring another question.

Thanks again,

Daryl

I think that may be Markus' problem too...

Len,

Do you ever have those days where one minute something works as expected, then not, then it does again? Well, I may be having one of those days...I just went and re-filled the area with ant-aliasing enabled and still obtained the 1-pixel errant fill. I'm in PSCS at the moment and will recheck the behavior with PS7.

OK...here's more info: Originally I observed this behavior while creating an action, using Select All and Transform Selection to establish 50% of my image as the area to fill. Performing the selection manually, I simply used the Marquee Tool and grabbed the desired rectangular region. When the fill is applied to the transformed selection, the error is introduced; when applied to the manually selected rectangle, it is not.

Any thoughts?

Daryl

Daryl,

I just went and re-filled the area with ant-aliasing enabled

You want to turn anti-aliasing OFF.

Feather set to 0.

Mathias

Mathias,

Thanks...but it seems there must be multiple factors involved depending upon the selection and fill technique used. In the case where I selected the area manually using the marquee tool, the anti-alias option wasn't available. Why, I'm not sure, but I didn't really pursue trying to figure that out at the time. And, from that observation I assumed, perhaps incorrectly, that Len actually mean anti-aliasing on the Fill Tool should be set. With that done, I did obtain a true fill edge-to-edge. I may explore this further but not tonight.

Thanks,

Daryl

Hi Daryl,

What I SHOULD have said was FEATHER set to zero on the Marquee tool - but it was late at night on a machine without Photoshop installed<g>

Len,

I can definitely understand those late night thoughts...thanks for the clarification. I did have feather at 0.

Cheers,

Daryl

Never noticed before, but I can't find any set of variables with the rectangular marquee where anti-alias is even an option. Is grayed out for retangular/single row/single column. Is an option for elliptical.

What am *I* missing here?

Mac

Mac,

I'd not given the question of anti-aliasing much thought yesterday, but it makes sense that any sort of rectangular selection would not be concerned with aliasing. Only non-linear selections would be affected. Similarly, it leaves me to wonder why selecting anti-aliasing for the Fill Tool allowed me to achieve a full edge-to-edge pure 0/0/0 black fill yesterday. Since the selection was rectangular, a fill should have been performed perfectly, aliasing or not.

Off to the lab...can't get sidetracked! Ha!

Daryl

Oh, duh on me...

I see you were talking about the FILL TOOL anti-alias option. I was looking at rect. marquee option.

I don't really understand the interaction between the two enough to offer anything else at this point ...

Mac