Re: presentations in ConTeXt

[Mojca Miklavec <mojca.miklavec.lists@gmail.com>]

On 5/23/05, Thomas A. Schmitz <thomas.schmitz@uni-bonn.de> wrote:

> I am still at a loss how to achieve one thing in ConTeXt that was
> pretty easy in Keynote or (shudder) Powerpoint: When I wanted to
> highlight something on a map or a picture, I would just draw a red
> circle around it. What would be the proper way to do this in ConTeXt?
> Adding a layer with a red circle drawn in Metapost, then positioning
> it by trial and error? Or can anyone point to a better solution?

What kind of picture do you have? If you have .jpg/.png/..., you can
get (x,y) position of the pixel where the center of circle should be.

One possibility is to create a new metapost figure and draw the circle
on it using the measured coordinates:

(This circles the blue tulip on
http://contextgarden.net/images/6/65/Kochloewe_c.jpg.)

\setupcolors[state=start]
\starttext
\startuseMPgraphic{CircleBlueTulip}
	% center point
	pair size, c;
	% figure will be 10 cm wide
	scale := 10cm/400;
	
	% center of the blue tulip is on (219,333), image is 400*460
	size := (400,460) scaled scale;
	c := (222,460-330) scaled scale;
	% diameter of the circle should be 50 pixels
	d := 50scale;

	pickup pencircle scaled 2pt;

	externalfigure "Kochloewe_c.jpg" xyscaled size;
	draw fullcircle scaled d shifted c withcolor red;
\stopuseMPgraphic

\useMPgraphic{CircleBlueTulip}

\stoptext

I believe there exists a more straightforward way if you make
uniqueMPgraphic and specify coordinate fractions of the circle to be
drawn, but if you say:

\framed[background=SomeGraphicWithACircle]{\externalfigure[Kochloewe_c][width=10cm]},
the circle (if any) is drawn behind the figure and cannot be used as
such. Unless you specify the figure in a new layer and draw both
layers in the proper order.

In this case it would be fine to have a \framed[...foreground=...] command :)

> And lastly: I have never seen transitions working on OS X (both
> Apple's Preview and Adobe Reader 7.0). Can anybody confirm that they
> got this working on other systems?

They work in Windows XP (I'n not sure if they're also working using
ConTeXt commands). But they are so ugly that you don't want to use
them.

Mojca