On 08/02/2005, at 1:13 PM, Geoffrey wrote:

Carol Spears wrote:
On Mon, Feb 07, 2005 at 07:51:01PM -0500, Geoffrey wrote:
I have been working with selecting sections of a photo so as to remove the background. Although it appears that I have selected the whole portion of the image, when I paste it to new, I see missing pixels. Is this a bug, or am I doing something wrong?

Point is, if I've missed some pixels, they should show up as not selected right?

Gimp 2.0.4

I've dropped the two images here if you would like to check them out. Note the missing pixels on the second image, (primarily on her legs and arms).


it would be easier to see the problem with the xcf saved with the
selection you used.

I put it on the site as well.

it is recommended that you work at 400% view so that you can see if
there are problems like this.

I looked at it at even a greater % and still could not see any pixels that were not in the selection.

another thing to do is to save the selection as a layer in your xcf so
you can fix any pixels problems like this, whether it is a problem with
the selection technique or with gimp.

Well, I used the clone tool to fix it up, but I'm still thinking there's a problem with GIMP.

It's a problem, but not so much a bug as a limitation of the 'crawling ants' view that shows a selection. Pixels aren't just 'selected' or 'not selected' in that image, there are some pixels which are 10% selected, 20, 50, 80, 100% selected, and so on. The crawling ants outline view of a selection however, doesn't show anything more than a binary representation - presumably with a cutoff of 50%, meaning you only see the dotted outline around pixels that are more than 50% selected, and those under 50% show as unselected, which includes the areas that are showing up as problems in the shins for example.

The Quick Mask mode gives a full representation of a selection, by overlaying a colour (red by default) in various shades to show a selection. For some example images, http://www.danamania.com/temp/ants.jpg is the normal dotted outline view of a selection, zoomed in around the legs. This shows nothing selected on the legs themselves, as some of those pixels are only partially selected.

A quick jump into Quick Mask mode (with Shift-Q or Select->Toggle Quick Mask) shows all though, and http://www.danamania.com/temp/quickmask.jpg indicates that there are some slightly red pixels on the shins, which represent areas that are only partially selected. Those are the ones that show up in Quick Mask mode, and not in the normal crawling ants view of a selection.

When in quick mask mode, you can fix this by 'drawing' a selection using the normal drawing tools such as the paintbrush. Drawing in 'black' will cause an area to become selected(red), and drawing in 'white' will cause an area to become unselected(non-red) - so while in Quick Mask mode, draw over the inside area of the legs with 'white' to unselect those partially selected pixels. You should see the red go away, and it'll look like this: http://www.danamania.com/temp/quickmaskfixed.jpg

Scroll around the image and look for any more of those partially red (partially selected) pixels - such as on elbows, and draw over those to clear them, hit shift-Q again, and you're back to the crawling ants view, able to delete the background as you did in the first place - but this time witho deleting those partially selected pixels you just fixed :).


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