On Monday, August 13, 2007 10:32:54 pm Jürgen Hubert wrote:

A minor annoyance I had to deal with is when I am attempting to use blur effects on layers with transparent areas - instead of assuming that the transparent areas have no color worth blurring at all, GIMP seems to assume that they are black for the purpose of the blurring algorithm - which can cause some rather ugly side effects.

To see what I am talking about, start with a new image with a white background. Create a new, transparent layer, and place a pure white object on it (such as a white circle). Now apply any blur function to it.

What you will see are some gray boundary areas around your white object, depending on what parameters you used for the blur effect.

That's not what I see. I started with a white background layer, added a transparent layer, created a circular selection, filled it with white, deselected the area, and used Gaussian blurring with a radius of 20. It behaved as it should, spreading out the pixels and gradually blending them to the transparent areas of the layer without affecting the color. The only way it becomes visible is if I toggle the visibility of the background layer.

Now in _my_ opinion, what ideally _should_ happen is that you see nothing at all in this case - the white of the object should be a bit more spread out with a greater graduation of the object's transparency in the boundary areas, but there shouldn't be any discolorations.

Is there some way to achieve this with GIMP?

On 8/14/07, Jürgen Hubert wrote:

A minor annoyance I had to deal with is when I am attempting to use blur effects on layers with transparent areas - instead of assuming that the transparent areas have no color worth blurring at all, GIMP seems to assume
that they are black for the purpose of the blurring algorithm - which can cause some rather ugly side effects.

To see what I am talking about, start with a new image with a white background. Create a new, transparent layer, and place a pure white object on it (such as a white circle). Now apply any blur function to it.

What you will see are some gray boundary areas around your white object, depending on what parameters you used for the blur effect.

What I see is white; and the preview confirms that the area is only becoming more diffuse, not discolored.
Your bug report is only meaningful if you mention what version of GIMP you're using. Otherwise this behaviour may have been fixed since the release you're using.

I am using the SVN version of gimp of last week.

On Tuesday 14 August 2007 04:11, David Gowers wrote:

On 8/14/07, Jürgen Hubert wrote:

A minor annoyance I had to deal with is when I am attempting to use blur effects on layers with transparent areas - instead of assuming that the transparent areas have no color worth blurring at all, GIMP seems to assume
that they are black for the purpose of the blurring algorithm - which can cause some rather ugly side effects.

To see what I am talking about, start with a new image with a white background. Create a new, transparent layer, and place a pure white object on it (such as a white circle). Now apply any blur function to it.

What you will see are some gray boundary areas around your white object, depending on what parameters you used for the blur effect.

What I see is white; and the preview confirms that the area is only becoming more diffuse, not discolored. Your bug report is only meaningful if you mention what version of GIMP you're using. Otherwise this behaviour may have been fixed since the release you're using.

I am using the SVN version of gimp of last week.

Actually, I recall this in gimp 1.2 - I guess this has been fixed in GIMP 1.3 devel cycle.

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