Re: 1. Input of screen coordinates; 2. Fast graphics

• To: mathgroup at smc.vnet.net
• Subject: [mg26964] Re: 1. Input of screen coordinates; 2. Fast graphics
• From: "Allan Hayes" <hay at haystack.demon.co.uk>
• Date: Tue, 30 Jan 2001 03:38:16 -0500 (EST)
• References: <94vs7q\$oa9@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Manuel,
I'm not quite sure of what you want, but you may find something of use in
the following.

Re question 1

cpd = ClipboardNotebook[];

Plot[Sin[x], {x, 0, 2Pi}];

- click on the cell holding the picture
-with Control key held down click on some points on the curve
- save (Control, S)
- get the coordinates of the clicked points

coords = NotebookGet[cpd][[1, 1, 1]];

Re question 2

Raster and RasterArray may help.

--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565

"Manuel Arala Chaves" <machaves at fc.up.pt> wrote in message
news:94vs7q\$oa9 at smc.vnet.net...
>
> I have two questions:
>
> 1st question - Is there a way in Mathematica to input a couple of screen
> coordinates with the mouse?
>
> The closest thing I know is: in a graphic, CTR+ALT+mouse shows the
> coordinates in the graphic. Or (rather artificial), if you have a picture
> inserted into the Mathematica notebook, you can move (with the mouse)
> another graphics window over the picture and look at the successive screen
> coordinates of the top left corner.
> But in both cases you cannot "save" the coordinates you see into a
> variable. Is this possible in another way?
>
> (What I need is the following: imagine you have a picture with a curve,
> inserted in a Mathematica notebook; I would like to be able
> to mark with the mouse enough points of the curve and then to use the
> coordinates of those points to fit a curve in Mathematica - preferably in
> parametric form - which would approximate the curve in the image). Any
> suggestion?
>
>
> 2nd question - Suppose you have an array 600x600 of numbers (of colors) in
> Mathematica and you want to get an image of a square (600x600 pixels),
> each pixel having a color depending on the number in the corresponding
> position of the array. (If Color is the array and MaxColor the maximum
> element of the array, the color of pixel {x,y} could be given by
> Graphics[Hue[Color[[x,y]]/MaxColor]]).
> Of course it is very easy to do that by appending instructions
> Graphics[Hue[color[[x,y]]/MaxColor]], Graphics[Point[[x,y]]], ... and for
> economy, if the color did not change, you may even suppress the color
> instruction. This works for small arrays, but it takes a lot of computing
> time if the array is big, e.g. 600x600.
> Is there a fast way of getting the picture?
> If not, I would consider saving the corresponding array to a
> file and using another program to view the image. Any suggestion?
>
> Thanks in advance.
>
> Manuel Chaves
>
>

```

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