ListDensityPlot and GraphicsArray

*To*: mathgroup at smc.vnet.net*Subject*: [mg65467] ListDensityPlot and GraphicsArray*From*: "buttgereit at biomediclab.de" <buttgereit at biomediclab.de>*Date*: Mon, 3 Apr 2006 06:59:33 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Dear Group, using Mathematica 5.0 on WinXP I have a strange problem with ListDensityPlot. I have imported a picture (PNG) using img=Import["mypic.png"]; I can show it, all fine so far. I then extract the pixel data (rgb in this case) using raster=img//First//First; I extract the red channel using rc=Map[First,raster,{2}]; and can display it with ListDensityPlot[rc]; However, when I convert the raster to Lab color space and extract, say the illumination ListDensityPlot[lc]; fails with "DensityGraphics::gmat: ... is not a rectangular array larger than 2 x 2" But the size is identical to rc according to Dimension[rc] is equal to Dimension[lc] : {400,300}. Just Reals instead of Integers -- and though, rounding/scaling does not make a difference. I have checked the array using Union[Length/@lc] which evaluates to {400} in this case -- doesn't this say it _is_ rectangular? Do I miss something? I can show part of the array using Take and define a region of at most 200x200 pixels -- expanding it again pops the error. I can move that "window" over the image without errors. Just expanding it does not work. Any idea what could cause the problem? ( yes, I did restart windows ;) Best Regards, Peter