Export RGB data (from a tiff image) in excel format

Question

I have a tiff file having 3 bands R, G, B. I used the following program in R to obtain the pixel values for each band separately.

r<- raster("lena.tiff", band = 1)
writeRaster(r, filename = "lenadd.asc", format = "ascii", datatype= 'INT4U')

It gave me an ascii file containing the pixel values for R band. Similarly, by changing the band value to 2 and 3, I can get the other two files. However, I want to export the data in excel format. But I suppose, writeRaster command doesn't support xlsx format. So, can someone please suggest me any alternative of writeRaster command so that I can export my RGB data in excel format?

I am new to R so pardon me if the question is too trivial.

Edited :

class : RasterLayer

band : 1 (of 3 bands)

dimensions : 512, 512, 262144 (nrow, ncol, ncell)

resolution : 1, 1 (x, y)

extent : 0, 512, 0, 512 (xmin, xmax, ymin, ymax)

coord. ref. : NA

data source : C:\Users\lenovo\Documents\lena.tiff

names : lena

values : 0, 255 (min, max)

Answer 1

Here is a function that uses raster and xlsx packages to write a multi-band raster to an Excel spreadsheet, one band per sheet, in a gridded format:

stack_to_xlsx <- function(rs, filename){
    w = createWorkbook()
    for(i in 1:nlayers(rs)){
        cs = createSheet(w, sheetName = paste0("Band-",i))
        dr = raster::as.data.frame(raster::as.matrix(raster(rs,i)))
        addDataFrame(
            dr,
            cs
            )
    }
    saveWorkbook(w, filename)
}

And here's a usage:

Use stack to read in all the bands:

> rs = stack("./preston.tiff")

This is quite a large tiff so I crop it down a bit:

> rsc = stack(crop(rs, extent(350172.7, 351308.5, 429508.1, 430840 )))
> dim(rsc)
[1] 118 100   4
> stack_to_xlsx(rsc, "crop.xls")
> 

Now open crop.xls in Excel (Or OpenOffice, that also works).