Re: Miscellaneous questions
- To: mathgroup at smc.vnet.net
- Subject: [mg36797] Re: Miscellaneous questions
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Thu, 26 Sep 2002 04:56:51 -0400 (EDT)
- Organization: Universitaet Leipzig
- References: <amrjfe$5av$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
> I would appreciate any info on these issues.
>
> 1. I have a symbol "slback." I was getting
> "tag times lback protected " (or something) errors.
> (A typically uninformative error message.)
> I suspected there was a separation between the s
> and l, and they looked too far apart, but when I
> spaced past them with the arrow keys, there did
> not appear to be anything like a space in between.
> I retyped the symbol and all was ok. This has
> happened before. What's going on ???
As long as you don't send us the *exact* input we can't
help you. You should also send the mathematica version
you are using. But typical this error comes from a equation
a*b==c
where the user has mixed up Equal[] and Set[]
>
> 2. I'm using Raster to plot data points
> in a 256x256 array. Two problems: First,
> regardless of the ImageSize setting (I need the
> display as big as possible), the individual data cells
> when examined closely at 300% vary in size by
> almost 2:1. This makes detailed inspection of the
> data values difficult. Surely there is some setting
> of something which would make each data cell an
> exact number of screen pixels? Second, I'm
> using
> Show[ Graphics[Raster[ rescol,
> ColorFunction -> Hue]],
> AspectRatio -> Automatic,
> ImageSize -> 700];
> but the Hues don't allow enough easily distinguishable
> shades to visually recognize even 6 data values easily.
> (I'm slightly colorblind.)
The most humans can distinguish 160 gray levels
>It would be nice to have black
> and white available for two of the data values, but Hue
> does not allow this.
And something like:
mycolor[i_] :=
Switch[Round[i],
0, RGBColor[0, 0, 0],
1, RGBColor[1, 0, 0],
2, RGBColor[1, 1, 0],
3, RGBColor[0, 1, 0],
4, RGBColor[0, 1, 1],
5, RGBColor[0, 0, 1],
_, RGBColor[1, 1, 1]]
Show[Graphics[
Raster[Table[Random[Integer, {0, 6}], {16}, {16}],
ColorFunction -> mycolor, ColorFunctionScaling -> False]]]
does not help ?
> I don't understand what the
> documentation says about RasterArray.
If you can't be more specific *what* you not understand
we can not help you.
>
> 3. I wanted to get this raster image into a format
> where I could dissect it with Photoshop or equivalent.
And ? waht does Export[] do ? it write the expression
in a desired format, TIFF, PNG, PPM are all lossless
compressed bitmap formats, that Mathematica can export
and that can be imported into PhotoShop
> After much fooling around, I found that I can export the
> selection as an html file, read it into Navigator, do File>
> Edit Page, which brings up Netscape Composer, right
> click the image which, allows saving it as a GIF, which
> I can finally work on with a photo editor. Maybe
> there is an easier way, or maybe this description will
> help someone with the same need.
May be that thhis description help someone who can't read
the fancy documation on Import[] and Export[].
Regards
Jens