Hi,
I've been playing with the Gaussian Blur filter for updating my book and have a couple of comments:
1. In the release notes it states that one can achieve a different blur in the vertical and horizontal directions by first stretching a path, then blurring it, and finally shrinking it back. This appears to work only if the path does not have a "transform" attribute after it is stretched. The SVG standard includes a provision for separate x and y blurring and Inkscape seems to have the code in nr_filter-gaussian.cpp to handle this; this seems to be a more natural way to achieve the desired result. A second blur slider could be added. Or what about using "Blur Handles" that function like the rectangle tool corner radius handles?
2. The term "Blur Radius" in the release notes should be defined. A look at the code reveals that it is the Standard Deviation of the Gaussian. This definition maybe has only meaning to the mathematically astute but one should be able to come up with a meaningful definition.
3. Why is a filter object created (or renamed) every time a blurred object is moved? The filter parameters don't change. Why would the filter object ever be renamed? This leads to the general question of how Inkscape handles SVG files that come from other sources. A number of people have complained about Inkscape mangling their files and I think that this is one example of that.
Tav
On 2/1/07, Tavmjong Bah <tavmjong@...8...> wrote:
- In the release notes it states that one can achieve a different blur
in the vertical and horizontal directions by first stretching a path, then blurring it, and finally shrinking it back. This appears to work only if the path does not have a "transform" attribute after it is stretched. The SVG standard includes a provision for separate x and y blurring and Inkscape seems to have the code in nr_filter-gaussian.cpp to handle this; this seems to be a more natural way to achieve the desired result. A second blur slider could be added.
Yes, when we have a dedicated filter tool, it should have a way to set x and y radii separately. But for now, isotropic blur is what is needed in a great majority of cases. We need to find a compromise between features and simplicity here because Fill&Stroke cannot accommodate everything. The squeezing trick is just that - a trick, for those who are curious or who need this desperately.
Or what about using "Blur Handles" that function like the rectangle tool corner radius handles?
Yes, this may be part of a filter tool's on-canvas UI.
- The term "Blur Radius" in the release notes should be defined. A look
at the code reveals that it is the Standard Deviation of the Gaussian. This definition maybe has only meaning to the mathematically astute but one should be able to come up with a meaningful definition.
Feel free to edit the rel notes. To me, "radius" is pretty self-explanatory, whereas "standard deviation" is a lot more obscure, but I won't object if you add a reference from the former to the latter.
- Why is a filter object created (or renamed) every time a blurred
object is moved? The filter parameters don't change. Why would the filter object ever be renamed? This leads to the general question of how Inkscape handles SVG files that come from other sources. A number of people have complained about Inkscape mangling their files and I think that this is one example of that.
It was just the cheapest and fastest way to make the blur functionality available. We never claimed proper support for non-Inkscape-created filters. For example if you have some filters on an object and blur it in Inkscape, all other filters will be lost. This all can and will be fixed with time, of course. We just need more people to work on that. If we waited until the entire filters system is correctly implemented, we'd never release 0.45.
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bulia byak -
Tavmjong Bah