Re: importing image and getting numbers from the gray intensity

*To*: mathgroup at smc.vnet.net*Subject*: [mg49445] Re: importing image and getting numbers from the gray intensity*From*: sean_incali at yahoo.com (sean kim)*Date*: Tue, 20 Jul 2004 07:53:43 -0400 (EDT)*References*: <cd5okp$b2c$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi everyone, follow up on Paul's, George's Jerry's and Yas' suggestions. Yes, it must be version dependent. I'm getting exactly what George is getting as well. In[4]:= $Version Out[4]= 5.0 for Microsoft Windows (June 12, 2003) And I named the input cell pixels, not pixel. And I'm getting Raster instead of RasterArray object I though I would be clever and change the Input to RasterArray, then it brings back... RasterArray::rscol: Expression 0.160784` at position {1, 1} in first argument \ of RasterArray is not a valid color or gray-level directive the numbers are not the same because I took the negative image from Irfanview image viewer. Also I noticed that if I take the negative image from irfanview and save it as jpg, non of the suggestions work, but that's not related to Mathematica, i don't think. it must be more of how irfanview encode the jpg images... IF I use Raster in your codes as George said and with the original image, In[16]:= pixels = First[Cases[pixels, Raster[x__] :> x, Infinity]] /. RGBColor[r_, g_, b_] :> (r + g + b)/3 ListDensityPlot[pixels,Mesh\[Rule]False]; then i get, {{0.839216, 0.839216,0.807843, ... long list of numbers ... 0.905882, 0.905882, 0.905882}} and the the original plot. here is something that is kinda weird for me, if I repeat evaluate that cell, In[18]:= pixels = First[Cases[pixels, Raster[x__] :> x, Infinity]] /. RGBColor[r_, g_, b_] :> (r + g + b)/3 ListDensityPlot[pixels,Mesh\[Rule]False]; From In[18]:= First::first: {} has a length of zero and no first element Out[18]= First[{}] From In[18]:= DensityGraphics::gmat: First[{}] is not a rectangular array larger than 2 x 2. And both Jerry and Yas used the columns to find the lanes. After trying the hint, I totally understand where you guys got the lane numbers. It tells you right on the picture. Mathematica must have taken the image and defined it in an array. so that the dimentions tells you how many Rows and Columns are in the array (i guess?) If I use a negative image, then the chromatograms you suggested looks much better, as you get peaks instead of dips. ListPlot3D[d, Mesh -> False, PlotRange -> All, AspectRatio -> Automatic, ImageSize -> 400] Above will really demonstrate the limitation of the gray levels human eye can perceive. if you look at the center of the bands, they seem to be of one intensity but Mathematica wil actually show you differing levels in the form of peaks! Anyway, thank you all very much. I'm starting to appreciate the power of Mathematica. it's pretty amazing. Even though I'm still not very good at it. (but I'm getting better thanks to this group) sean Hi Paul (Jean and Sean), Thanks for the clarification on how the function works. Also, from your post to Sean, I realize now that my issue was that my Mathematica version: In[8]:= (9:08:18 on 7/19/04) $Version Out[8]= (9:08:18 on 7/19/04) 5.0 for Microsoft Windows (June 10, 2003) returns a "Raster" object. So simply using Raster[x__] in place of RasterArray[x__] makes it work. Thanks greatly, George -----Original Message----- From: Paul Abbott [mailto:paul at physics.uwa.edu.au] To: mathgroup at smc.vnet.net Subject: [mg49445] RE: [mg49371] Re: importing image and getting numbers from the gray intensity Hi George: >I suppose this is terrible etiquette. I do not use post groups like >this often. But, since I discovered this (through your "In and Out", I >have become rather addicted to the group. I'm glad that you like MathGroup >I am very interested in your response to this post. However, I do not >understand it. I am okay up to getting the following into my cell: > >pixels=Show[Graphics[{ >AbsoluteThickness[1], >Raster[{ >{0.827451,.... 0.882353}}, >{{4, 4}, {254, 293}}] >}], AspectRatio->1.156, >PlotRange->{{4, 254}, {4, 293}}, >ImageSize->{250, 289}] That looks fine to me. >But, then I do not understand what part of this expression I assign to >"pixels". As you have done above (typing "pixels=" into the InputForm cell). >Perhaps my confusion is due to another issue, which is that I have >never named a Cell, and therefore, I assume I should name part of the >above expression "pixels". I made a couple of attempts, such as: > >pixels={{0.827451,.... 0.882353}}; > >Or > >Pixels=Raster[{{0.827451,.... 0.882353}},{{4, 4}, {254, 293}}]; You could do either of these things. The idea I was presenting here is to assign pixels to be the full graphic object (the result of the Show[] command) and then use Mathematica commands to extract from this graphic the information giving the colors by _overwriting_ the value of pixels using pixels = First[Cases[pixels, RasterArray[x__] :> x, Infinity]] /. RGBColor[r_, g_, b_] :> (r + g + b)/3 >However, I am having no success with your function. Also, you can see >that part of my problem is that I do not understand in totality, the >syntax of your command. You can de-construct this command as follows. The inner part Cases[pixels, RasterArray[x__] :> x, Infinity] locates the RasterArray in pixels and saves its argument, x. There are two parts to the RasterArray but only the first part is relevant, extracted using First. Then, for each color primitive RGBColor[r, g, b] we average the r,g,b values using the replacement rule RGBColor[r_, g_, b_] :> (r + g + b)/3 Then we call the result of this pixels (overwriting its earlier value). As a check we re-draw the picture ListDensityPlot[pixels, Mesh -> False]; Cheers, Paul This message may contain privileged and/or confidential information. If you have received this e-mail in error or are not the intended recipient, you may not use, copy, disseminate or distribute it; do not open any attachments, delete it immediately from your system and notify the sender promptly by e-mail that you have done so. Thank you.

**Follow-Ups**:**Re: Re: importing image and getting numbers from the gray intensity***From:*Yasvir Tesiram <yat@omrf.ouhsc.edu>

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**Re: importing image and getting numbers from the gray intensity**

**Re: Re: importing image and getting numbers from the gray intensity**