cutting a sharp hole through a blurred object
I haven't been able to figure out a way to do this, but my inkscape skills aren't too strong.
I have a drawing that at the lowest level has an irregular glow. It's a freehand path-based polygon with a heavy blur on it. The blur is all alpha. On top of this is path-based, alpha=1 object; nothing special.
I need to knockout an interior region of this to an alpha of zero. It's easy to knockout the alpha=1 object with path difference. However, I can't figure out how to cut a hole in the underlying glow-producing path. It's easy enough to do the path difference, but this actually cuts a hole in the glow-producing path which then blurs into the interior, the part I want to be alpha=0.
What I'd like to do is kinda multiply the alpha channel of two paths/groups.
The (incorrect) approximation of this is to take the png that I produce at the end and map a particular color to the alpha channel. This doesn't handle the anti-aliased edges correctly.
Any suggestions?
On Mon, 14 Feb 2011 10:40:31 -0800 Steven Parkes <smparkes@...2812...> wrote:
I need to knockout an interior region of this to an alpha of zero. It's easy to knockout the alpha=1 object with path difference. However, I can't figure out how to cut a hole in the underlying glow-producing path. It's easy enough to do the path difference, but this actually cuts a hole in the glow-producing path which then blurs into the interior, the part I want to be alpha=0.
Draw a large rectangle over your blurred thing which more than covers it, including the blur. Make a hole in this rectangle where you want the hole in the object, using path difference. Then select the blurred object and the rectangle with a hole in it, and do Object -> Clip -> Set.
Cheers -Terry
Perfect. Seems so simple in retrospect. Thanks!
On Feb 14, 2011, at 1:04 PM, Terry Brown wrote:
On Mon, 14 Feb 2011 10:40:31 -0800 Steven Parkes <smparkes@...2812...> wrote:
I need to knockout an interior region of this to an alpha of zero. It's easy to knockout the alpha=1 object with path difference. However, I can't figure out how to cut a hole in the underlying glow-producing path. It's easy enough to do the path difference, but this actually cuts a hole in the glow-producing path which then blurs into the interior, the part I want to be alpha=0.
Draw a large rectangle over your blurred thing which more than covers it, including the blur. Make a hole in this rectangle where you want the hole in the object, using path difference. Then select the blurred object and the rectangle with a hole in it, and do Object -> Clip -> Set.
Cheers -Terry
participants (2)
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Steven Parkes -
Terry Brown