Magic Wand still recognizes pixels I know I erased

[Rosie J]

When I make lineart, I often use the Magic Wand tool to select the lines themselves if I want to move part of the lineart without erasing and redrawing. The default Tolerance (50%) does not work; it selects only the darkest pixels in the lines and leaves behind a grayish shadow on either side of the line's former location. I am using the Line/Curve tool set to Spline for most of the lineart, and my Paintbrush is set at maximum Hardness, but there appears to be no way to get a perfectly black and white image with the Line/Curve tool. (I don't have a functional tablet and stylus at the moment, so the Pencil tool is mostly useless to me at this time.) "Not a problem," I thought. "I'll just set the Tolerance higher so Magic Wand will grab the whole line, not just the middle of it." Which I did. And then I noticed something very strange.

The Magic Wand selected all the lines I'd drawn, as I expected. It also selected what appeared to be every stroke of the Eraser tool that I had used when making the lineart. All over the image were invisible brushstrokes, outlined in the 'marching ants' selection, that I recognized as being where I had erased lines that I hadn't been able to move. I double checked that my eraser's Hardness and Opacity were set to maximum, they had been all along. I had used the eraser set to (I think) 5 pixels, while all the lines had been drawn with the Line/Curve tool set to 2 pixels.

It appeared that the eraser tool was leaving smudges of not-quite-transparent pixels wherever I used it--pixels the Magic Wand could see but I couldn't. Setting my eraser size larger (13 pixels if I recall right) seems to have gotten rid of these smudges. In hindsight I realize I should have taken a screenshot before doing so, but I found an area that still had some smudging in places with too many lines too close together to use the 13-pixel-wide eraser and took two screenshots (attached): one of the image as it appeared to me and one with Magic Wand used on the lines at somewhere between 60 and 85% tolerance.

In a nutshell, the problem appears to be that the eraser, even set to 100% Hardness and 255 Opacity (Alpha), is not completely erasing pixels where it is used, at least when it is less than ten pixels wide.

[LoudSilence]

19 minutes ago, Rosie J said:

leaves behind a grayish shadow on either side of the line's former location. I am using the Line/Curve tool set to Spline for most of the lineart, and my Paintbrush is set at maximum Hardness, but there appears to be no way to get a perfectly black and white image with the Line/Curve tool.

 

20 minutes ago, Rosie J said:

It appeared that the eraser tool was leaving smudges of not-quite-transparent pixels wherever I used it

This is because Anti-Aliasing is on, to turn it off, select the eraser, line tool, or paintbrush tool, go to the top where you control the hardness, and press this icon: , clicking that should turn off anti-aliasing so these "not-quite-transparent pixels" and grayish shadow dont appear anymore. The icon should turn into this:

[Djisves]

@Rosie J, assuming that you draw your lines on an otherwise transparent layer, before using the Magic Wand, run @Red ochre's Alpha-threshold plugin to get rid of near transparent pixels. (Part of Red ochre plugin pack 10.1).

 

But I would not do it your way. In this situation it is far better to use any of the other selection tools, i.e. rectangle, lasso, eclipse. Given the shapes of the lines in your example, the Lasso selection tool would be my first choice. You can get much cleaner and more precise selections if you avoid the Magic Wand.

[Rosie J]

15 hours ago, Djisves said:

But I would not do it your way. In this situation it is far better to use any of the other selection tools, i.e. rectangle, lasso, eclipse. Given the shapes of the lines in your example, the Lasso selection tool would be my first choice. You can get much cleaner and more precise selections if you avoid the Magic Wand.

Thanks, but as I don't have a tablet, Lasso is very unpredictable. Trying to accurately outline, say, an eye I've drawn with the mouse has not yielded good results. I've been fiddling with the Magic Wand's Tolerance using the + and - buttons, which seems to have helped a lot.

[Rosie J]

On 10/23/2020 at 5:14 PM, LoudSilence said:

 

This is because Anti-Aliasing is on, to turn it off, select the eraser, line tool, or paintbrush tool, go to the top where you control the hardness, and press this icon: , clicking that should turn off anti-aliasing so these "not-quite-transparent pixels" and grayish shadow dont appear anymore. The icon should turn into this:

Ah, thanks! I will try that!

(And it's "anti aliasing"? I thought it was one word pronounced "an-she-a-lie-zing". Anti Aliasing makes a lot more sense, haha)

[Ego Eram Reputo]

Another thing you might try: Select the areas around the lines with the Magic Wand + the Shift key (= global selection). This will select the areas in between the lines. Use the Tolerance to make sure you have just the lines selected - then press delete.

[Djisves]

4 hours ago, Rosie J said:

Trying to accurately outline, say, an eye I've drawn with the mouse has not yielded good results.

I think you're missing the point. Your workflow can be improved and things can me made a lot easier if you use transparent layers.

1. Draw your lines/eye on a transparent layer.

2. Zoom in and select around the object (line or eye) you want to move. You can select the transparent pixels around your object, do not have to be very accurate with your selection. You only need to be accurate if and where your "object" touches other "objects". For more accuracy, use a zoom of 800% or more. 

3. CUT your selection and PASTE in a NEW LAYER. The transparent pixels you have cut and pasted into the new layer will not erase any of the lines you want to keep (and that's why you do not need to be very accurate when making the selection). 

4. Move your pasted object using the Move tool and place it exactly where you want it.

Repeat steps for all lines / objects you want to move.