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readGDAL or raster for reading bit map files
4 messages · Michael Sumner, Alaios
Just do m <- as.matrix(store) or m <- as.image.SpatialGridDataFrame(store)$z image(m) They give the same result with different orientations. Note that both assume a single-band raster, e.g. you only have a "greyscale" bitmap (for example). The details behind all this is given in the documentation for the sp package. See ?image for the basic image plot for a matrix. Cheers, Mike.
On Thu, Nov 24, 2011 at 11:50 PM, Alaios <alaios at yahoo.com> wrote:
Dear all, I have asked yesterday of how I can read a simple bitmap file in R cran. I was suggest to use either readGDAL or raster for loading my bitmap a. I have done it with readGDAL like ??? store<-readGDAL(fname='lena256.bmp') ??? and it works,... but it converts my matrix-like notion of a bitmap to a large vector b. Raster also returns a class that I can not understand. So 1, I want to load it and keep the image as a matrix (so every cell in the matrix will correspond to a pixel) 2. I want to be able to plot the image based on that matrix that I have loaded too. Could you please explain me how I can do those? B.R Alex ? ? ? ?[[alternative HTML version deleted]]
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Michael Sumner Institute for Marine and Antarctic Studies, University of Tasmania Hobart, Australia e-mail: mdsumner at gmail.com
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It is by magic, otherwise known as R classes and methods. See
sp:::as.matrix.SpatialGridDataFrame
There's a lot of background here so I suggest you start with the
general R documentation, and the sp package documentation, including
vignette("sp")
and these
citation("sp")
Cheers, Mike.
On Fri, Nov 25, 2011 at 1:49 AM, Alaios <alaios at yahoo.com> wrote:
Thanks a lot! That worked. I have two R related questions when I use the ? store<-readGDAL(fname='lena256.bmp') this returns the struct below
str(store)
Formal class 'SpatialGridDataFrame' [package "sp"] with 6 slots ? ..@ data?????? :'data.frame': 65536 obs. of? 1 variable: ? .. ..$ band1: int [1:65536] 255 255 255 255 255 255 255 255 255 255 ... ? ..@ grid?????? :Formal class 'GridTopology' [package "sp"] with 3 slots ? .. .. ..@ cellcentre.offset: Named num [1:2] 0 -722925 ? .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y" ? .. .. ..@ cellsize???????? : num [1:2] 2835 2835 ? .. .. ..@ cells.dim??????? : int [1:2] 256 256 ? ..@ grid.index : int(0) ? ..@ coords???? : num [1:2, 1:2] 0 722925 -722925 0 ? .. ..- attr(*, "dimnames")=List of 2 ? .. .. ..$ : NULL ? .. .. ..$ : chr [1:2] "x" "y" ? ..@ bbox?????? : num [1:2, 1:2] -1418 -724342 724342 1418 ? .. ..- attr(*, "dimnames")=List of 2 ? .. .. ..$ : chr [1:2] "x" "y" ? .. .. ..$ : chr [1:2] "min" "max" ? ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots ? .. .. ..@ projargs: chr NA How the "R" when I run image(store) plots the lena correct. Where it store how the file was originally? Also when I do str(as.matrix(store)) this takes only the data and transforms them to the original matri str(as.matrix(store)) ?int [1:256, 1:256] How it does that? Looks as "magic" to me.... B.R Alex
________________________________ From: Michael Sumner <mdsumner at gmail.com> To: Alaios <alaios at yahoo.com> Cc: "R-help at r-project.org" <R-help at r-project.org> Sent: Thursday, November 24, 2011 2:25 PM Subject: Re: [R] readGDAL or raster for reading bit map files Just do m <- as.matrix(store) or m <- as.image.SpatialGridDataFrame(store)$z image(m) They give the same result with different orientations.? Note that both assume a single-band raster, e.g. you only have a "greyscale" bitmap (for example). The details behind all this is given in the documentation for the sp package. See ?image for the basic image plot for a matrix. Cheers, Mike. On Thu, Nov 24, 2011 at 11:50 PM, Alaios <alaios at yahoo.com> wrote: Dear all, I have asked yesterday of how I can read a simple bitmap file in R cran. I was suggest to use either readGDAL or raster for loading my bitmap a. I have done it with readGDAL like ??? store<-readGDAL(fname='lena256.bmp') ??? and it works,... but it converts my matrix-like notion of a bitmap to a large vector b. Raster also returns a class that I can not understand. So 1, I want to load it and keep the image as a matrix (so every cell in the matrix will correspond to a pixel) 2. I want to be able to plot the image based on that matrix that I have loaded too. Could you please explain me how I can do those? B.R Alex ? ? ? ?[[alternative HTML version deleted]] ______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. -- Michael Sumner Institute for Marine and Antarctic Studies, University of Tasmania Hobart, Australia e-mail: mdsumner at gmail.com
Michael Sumner Institute for Marine and Antarctic Studies, University of Tasmania Hobart, Australia e-mail: mdsumner at gmail.com