Create Landoltring with transparent background

Hello everybody,

I'm dealing with this question quite a long time. For an experiment I need to have a Landoltring ( http://en.wikipedia.org/wiki/Landolt_ring ) with a transparent background. I already tried to set the background of an existing image to transparent, but this procedure resulted in a unclear image especially at the borders of the ring.

Therefore, I was told the best way to handle is, to create a new Landoltring on a transparent background. Unfortunately I don't know how to do this?

Would somebody help me? I am a newby in MatLab and can only create Rings at the Moment, but I have no idea how to create gaps in the ring or set the whole background transparent.

The gap width is 1/5 of the diameter and so is also the stroke width. Perhaps it is possible to create a circle with a certain stroke width. The problem is that I don't know how to program a gap into it...

Any help would be highly appreciated.

Cheers, Ferdinand

Answer 1

[Image Analyst]

What is "under" the background? Just windows desktop, other programs, and various clutter like that? Why do you want it to be transparent rather than solid?

You can easily make up a "C" shape with the FAQ on how to create a circle: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F Just create two arcs, and stitch together the ends to form a thick "C" shape. Let us know if you can't do that.

[Ferdinand]

Hello, I need it to be transparent, because I want to use it in multiple experiments with different background colors of the monitor. In order to have a nice presentation of the ring it would be useful to only have the ring in black and no other background color. I will try your advise :) Thanks.

[Image Analyst]

It would be far easier just to make up images with the C's on a background of uniform color than to do the same on a transparent background and then create a uniform background of some color and then place your transparent+C image on top of it.

[Ferdinand]

Ok thank you for your advise. Unfortunately, I was reading the FAQ page, but am still a bit lost in creating the C I was of course able to create normal circles but I can't handle the thing with the gap ...

[Image Analyst]

Well if you're doing that, then why not just write a block to cover up part of it? Show your code so far.