On Thu, 2008-05-15 at 11:42 +1000, Hedley Finger wrote:
I want to create a representation of the HSV cone similar to that at http://en.wikipedia.org/wiki/Image:HSV_cone.png to show how it is derived from the CIE 1931 chromaticity diagram http://en.wikipedia.org/wiki/Image:CIExy1931.svg. I want all the labels, arrows, and the wedge cut-out in this graphic -- which is unfortunately a PNG and not a vector graphic -- to be removed.
If have tried using the clone tool to obliterate the unwanted arrows and letters, but cannot get a clean blend, not even with a blurred brush tool. One approach would be to treat a vector circle as the top of an apple pie, and create a series of wedges like slices. Then, in each wedge (slice), create a gradient from the edge to the tip. But I can't figure out how to blend adjacent wedges.
Nothing like waking up to a new challenge!
Make each wedge with a little bit larger radius than your final ellipse. Group all the wedges (Ctrl-G), go to the Fill and Stroke dialog (Shift-Ctrl-F) and use the blend slider. Add an extra ellipse with your final ellipse size. Select both the wedge group and the ellipse and use the Object->Clip->Set command to clip the group.
Is there another approach to get a continuous rainbow of colours around the perimeter of the circle, and then do a radial blend from white in the centre to the perimeter?
Try creating a new ellipse with a radial gradient from white with full opacity to white with full transparency put on top. (Don't use gradients for constructing the wedges in this case.)
To make the wedges, you can use the Tile Clones dialog to create a circle of wedges which after being grouped could be turned into an ellipse. The dialog does allow for automatically giving each wedge a different hue but I am not sure the hue shift is done properly. I've attached a quick try at using this method.
Alternatively, one could write a little perl/python script to generate each wedge with the correct color. Inkscape does support the Color Matrix filter which can rotate a hue in HSL space. It does so with a complex formula from the SVG specification.
Tav
