Author Topic: Unwanted outline  (Read 1588 times)

javierdl

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Unwanted outline
« on: March 30, 2014, 08:27:57 pm »
I am using a PNG with transparency around the actual subject. The problem is that I get an unwanted outline around the subject. It can be seen right in Scribus, before I export actually.
On a second attempt I stroked the outside edge with white using Gimp, and still the unwanted outline was there.

Below screenshots show: 1- what it looks like from Scribus, and 2- what it looks like from Adobe Reader, respectively





Any ideas?

Thanks guys,

JDL

GarryP

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Re: Unwanted outline
« Reply #1 on: March 31, 2014, 02:54:53 pm »
JDL, the problem looks like what you get if the transparency was created in GIMP - or whatever - with feathering on the tool - either on the brush or using the wand, etc. If you look more carefully in GIMP - for example, zoom right in and put a coloured layer below it - you'll probably see where the transparency isn't 100% at the pixels where the line is. (You'll see the "checkerboard" slightly coloured or lighter than normal.)

I believe that painting over the outline in white won't get rid of it because the transparency is on the alpha channel so it's making the white semi-transparent. Or something like that, I can't remember the exact terminology.

One simple way to get rid of the outline is to go over it on the alpha channel with a "hard" (i.e. no feathering) brush with the eraser tool - or whatever you want to use - to wipe it out. Another is to select the slightly smaller area within the line and do more cropping.

Or you could remove the alpha channel and fill the background in white, manually going over the outline area in white with a brush if needed.

Apologies if my explanation isn't great on the jargon front but I'm in no way an expert GIMP user. It's just that I can remember having a very similar problem myself a while ago and I tried a few of the above things to get rid of it.

Either way I believe the problem is with the PNG and not Scribus so you might get more joy from the GIMP forum if none of the above works - or even sounds right.

I hope this helps, or maybe a real expert can give you a better explanation.

Without the original image it's difficult to test my vague "solutions".

javierdl

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Re: Unwanted outline
« Reply #2 on: April 02, 2014, 01:01:44 am »
GarryP,
Ofnuts from Gimpforums.com kindly suggested for me to read this thread on how to control the sharpness of edges, I think. I'll start there.

JDL

GarryP

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Re: Unwanted outline
« Reply #3 on: April 02, 2014, 02:26:29 pm »
I'm glad you've been able to get some proper advice. I've now bookmarked that page myself - to look at properly when I get a chance - because it looks very informative. Thanks for posting it.

 

palmate