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Site Graphics and Multimedia Design Forum

Highlighting part of an image by fading the rest
Using GIMP

 1:21 pm on Aug 15, 2007 (gmt 0)

Unfortunately I'm not much of a graphics person, so I haven't been able to explain to the search engines what exactly I want to do, but I'm sure it must be possible.

Say I have a screenshot, and I wish to highlight a line or two of text. I could just hand-draw a crude red line around the area, but that's so Windows 3.1 ;-). What I would like to do is highlight the area by marking it, then having the surrounding area "fade out" by toning down all the colors. I'm sure I've seen the effect somewhere.

I suspect this has something to do with layers and channels, but I'm at a loss as to the terminology. I'd be so happy if anyone could give me any sort of pointers, e.g. a link to a tutorial, or even just the name / a concise way of describing what I want to do.

I usually work with GIMP (though not much beyond image resizing); if necessary I can get access to Photoshop.



 6:14 pm on Aug 15, 2007 (gmt 0)

Do you want the selection to be highlighted based on a user action, (click, mouse-over) or just run on a loop?


 6:55 pm on Aug 15, 2007 (gmt 0)

No, I just want to use this to process a static image so one part of it is "highlighted" (no animation,loops or anything fancy).

[edited by: zCat at 6:55 pm (utc) on Aug. 15, 2007]


 7:15 pm on Aug 15, 2007 (gmt 0)

I'm not sure about GIMP, but I know that in Photoshop this can be achieved quite easily.

1. Get the paintbrush tool
2. Choose black from the color palette
3. Reduce the opacity of the brush
4. Paint over the areas you wanted shaded / grayed out


 7:23 pm on Aug 15, 2007 (gmt 0)

Aha, "opacity" sounds like a word I need.

What I want to do is select e.g. a square or oval area, then make everywhere outside of the selected area opaquer / less colorful.

(What I'm doing is illustrating which item to pick in a drop-down menu; so I have a screenshot of the menu, and want to "highlight" one or two items).


 7:29 pm on Aug 15, 2007 (gmt 0)

So you just need to encapsulate the area you want to stand out with the marguee tool ( rectangle, circle ). Then select the inverse ( ctrl + I ) and go to town with the paintbrush.


 7:32 pm on Aug 15, 2007 (gmt 0)

A bit of gaussian blur outside the area you want highlighted will do a bit of highlighting in a very simple way. Not as good as other methods, but easy.


 8:19 pm on Aug 15, 2007 (gmt 0)

For a more uniform opacity change, follow the previous steps to have an inverse selection of the area you'd like to highlight. Cut it out and paste it on a new level, then just adjust that entire layer's opacity.


 1:19 pm on Aug 16, 2007 (gmt 0)

Ok, many thanks for the suggestions everyone, I have worked out more-or-less how to do it. "Inverse selection" was the key thing; once I'd worked that one out, the rest was fairly simple.

(Yes, I know it sounds obvious, but it's one of those things I've never done before. Must... find... some... time... to learn this all properly).

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