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MathGroup Archive 2001

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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg26972] Re: 1. Input of screen coordinates; 2. Fast graphics
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 30 Jan 2001 03:38:22 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <94vs7q$oa9@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

I can't answer your first question, 

Look into the Raster[] outpur if you read a palette
image (GIF's) The color function is a huge switch statment
with the palette. in you case it may help
but

yourPalette={3,5,67,255,196,...};
Show[
Graphics[
  Raster[your600x600Array,ColorFunction->(Hue[yourPalette[[#]]/MaxColor]
&)]
 ]
]

Hope that helps
  Jens

> 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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