Multicoloured radial gradient -- how to?

[Hedley]

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.

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?

I use The Gimp for pixmaps and Inkscape for vector graphics, and also
Scribus.  If you don't have experience with these programs, can you
describe what to do in general terms, not in specific PhotoShop,
Illustrator, or InDesign terms.  It shouldn't be too hard to translate a
general description into the necessary actions.

Regards,
Hedley

--

Hedley Finger

28 Regent Street   Camberwell VIC 3124   Australia
Tel. [phone]   Fax. (call phone first)
Mob. (cell) [phone]
Email. "Hedley Finger" <hfinger@...>

[Hedley]

microUgly:

>> 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?
>>    
> If it doesn't have to be vector then do it in GIMP.  On your canvas, create
> a circle select and fill it with the "Full saturation sectrum" gradient
> using the shape, "conical (asym)".  Then select a white to transparent
> gradient and fill the same circle with the "radial" shape selected.  With
> the circle still selected, transform (or scale) it so it's an oval.  Huzaah!
>  

Well, I got my ellipse with rainbow perimeter converging to white at the
centre just great!

I want this ellipse to be the flat top of an inverted cone, with the
colours on the visible "side" of the cone converging to black at the
point, similar to the HSV inverted cone in
<http://en.wikipedia.org/wiki/Image:HSV_cone.png>, but without all the
labels and arrows.

Extrapolating your directions for the ellipse above, I created a rainbow
gradient from one side of the ellipse to the other just fine.  I created
a square that has the left edge green and transforms through a number of
colours to purple on the right edge.

Then I tried to squeeze the black base of the square to a point halfway
from left to right on the bottom edge using the Perspective (keystone)
tool.  After reading section 4.8, 'Perspective", I select the entire
graphic, double-click the Perspective tool, set

@    Direction  (.) Normal
@    Interpolation: [Cubic  ]
@    Clipping: [Crop to result   ]
@    Preview: [Image + Grid   ]
@   [ Number of grid lines   ]  [11]

Then I click on the graphic and move the bottom L handle to the middle
of the bottom edge, and the bottom R handle also to the middle of the
bottom edge so that there is a very short edge.  The horizontal grid
lines are parallel with the bottom edge.  Then I click the Transform
button and ... nothing happens.

So how to get the graphic to narrow from top to bottom?

Regards,
Hedley

--

Hedley Finger

28 Regent Street   Camberwell VIC 3124   Australia
Tel. [phone]   Fax. (call phone first)
Mob. (cell) [phone]
Email. "Hedley Finger" <hfinger@...>



[Non-text portions of this message have been removed]

[Greg-123]

--- Hedley Finger <hfinger@...> 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.

Go to the following address, scroll down a bit and you'll find a pic of
the HSV cone.  Click on it and you'll get a bigger pic.  Click on it
again and you'll get the full size version.  Then just copy it and BAM,
you're all set.

     http://www.esri.com/news/arcuser/0807/nongeo.html

In case your wondering, I just Googled "HSV Cone" and after checking a
few links, there it was.

Hope it helps.