Read raster data as nativeRaster

read_to_nativeRaster() will read from a raster dataset that is already open in a GDALRaster object and return a nativeRaster object suitable for fast rendering. By default, it attempts to read the full raster extent at full resolution.

Usage

read_to_nativeRaster(
  ds,
  xoff = 0,
  yoff = 0,
  xsize = ds$getRasterXSize(),
  ysize = ds$getRasterYSize(),
  out_xsize = xsize,
  out_ysize = ysize
)

Arguments

ds

An object of class GDALRaster in open state, with 1, 3, or 4 bands of Byte data type.

xoff

Integer. The pixel (column) offset to the top left corner of the raster region to be read (zero to start from the left side).

yoff

Integer. The line (row) offset to the top left corner of the raster region to be read (zero to start from the top).

xsize

Integer. The width in pixels of the region to be read.

ysize

Integer. The height in pixels of the region to be read.

out_xsize

Integer. The width in pixels of the output buffer into which the desired region will be read (e.g., to read a reduced resolution overview).

out_ysize

Integer. The height in pixels of the output buffer into which the desired region will be read (e.g., to read a reduced resolution overview).

Value

An object of class nativeRaster.

Details

The dataset must have 1, 3, or 4 bands of Byte data type. For 1-band (grayscale) data, the value is replicated across RGB channels. For 3-band data, bands are interpreted as RGB. For 4-band data, bands are interpreted as RGBA.

Note

By default, this function will attempt to read the full raster into memory. It generally should not be called on large raster datasets using the default argument values. Use out_xsize and out_ysize for quick setting to smallish values, such as 1024.

See also

read_ds(), GDALRaster$readToNativeRaster()

Examples

# read an RGB image as nativeRaster
img_file <- system.file("help/figures/logo.png", package="survival")
if (file.exists(img_file)) {
ds <- new(GDALRaster, img_file)
r <- read_to_nativeRaster(ds)
bb <- ds$bbox()  ## will warn for non-spatial image but is harmless
ds$close()
plot(NA, xlab = "", ylab = "", asp = 1, xlim = bb[c(1, 3)], ylim = bb[c(2, 4)])
rasterImage(r, bb[1], bb[2], bb[3], bb[4])
}
#> Warning: failed to get geotransform, default returned