GDALReadOnlyDataset-class {rgdal}R Documentation

Class "GDALReadOnlyDataset"

Description

GDALReadOnlyDataset is the base class for a GDAL Dataset classes. Only read operations are supported. Both GDALDataset and GDALTransientDataset inherit these read operations while providing additional write operations (see GDALDataset-class). GDALReadOnlyDataset-class inherits from GDALMajorObject-class.

Usage

GDAL.close(dataset)
GDAL.open(filename)
getDriver(dataset)
displayDataset(x, offset = c(0, 0), region.dim = dim(x),
                           reduction = 1, band = NULL, col = NULL,
                           max.dim = 500, ...)
getColorTable(dataset, band = 1)
getGeoTransFunc(dataset)

Arguments

dataset An object inheriting from class 'GDALReadOnlyDataset'
filename A string giving the file to read from
x An object inheriting from class 'GDALReadOnlyDataset'
offset Number of rows and columns from the origin (usually the upper left corner) to begin reading from
region.dim The number of rows and columns to read from the dataset
reduction scaling parameter for region.dim
band The band number (1-based) to read from
col a vector of colours or a colour function such as rainbow
max.dim another scaling parameter
... other plotting parameters passed through

Details

GDAL.open and GDAL.close are shorter versions of new("GDALReadOnlyDataset", ...) and closeDataset(). Because GDAL.close through closeDataset() uses the finalization mechanism to destroy the handles to the dataset and its driver, messages such as:

"Closing GDAL dataset handle 0x8ff7900... destroyed ... done."

may appear when GDAL.close is run, or at some later stage. getDriver returns an object inheriting from class 'GDALDriver'. displayDataset and its use in plot for a pixmap object to produce a plot of the dataset, returning a pixmap object. getColorTable returns the dataset colour table (currently does not support RGB imaging). getGeoTransFunc returns a warping function.

Objects from the Class

Objects can be created by calls of the form new("GDALReadOnlyDataset", filename, handle). ~~ describe objects here ~~

Slots

handle:
Object of class "externalptr", from class "GDALMajorObject" ~~

Extends

Class "GDALMajorObject", directly.

Methods

closeDataset
signature(dataset = "GDALReadOnlyDataset"): ...
dim
signature(x = "GDALReadOnlyDataset"): ...
initialize
signature(.Object = "GDALReadOnlyDataset"): ...

Author(s)

Timothy H. Keitt, modified by Roger Bivand

References

http://keittlab.bio.sunysb.edu/R/GDAL/, http://www.remotesensing.org/gdal/

See Also

See also GDALDriver-class, GDALDataset-class, GDALTransientDataset-class.

Examples

logo <- system.file("pictures/logo.jpg", package="rgdal")[1]
x <- new("GDALReadOnlyDataset", logo)
dim(x)
plot(density(getRasterTable(x)$band1))
displayDataset(x)
displayDataset(x, col=function(x){rev(cm.colors(x))})
im <- displayDataset(x, col=function(x){rev(cm.colors(x))}, reset.par=FALSE)
contour(1:attr(im, "size")[2], 1:attr(im, "size")[1],
 t(attr(im, "index"))[,attr(im, "size")[1]:1], nlevels = 1,
 levels = 100, col = 'black', add = TRUE)
GDAL.close(x)
logo <- system.file("pictures/Rlogo.jpg", package="rgdal")[1]
x <- new("GDALReadOnlyDataset", logo)
dim(x)
displayDataset(x)
GDAL.close(x)
[Package rgdal version 0.4-4 Index]