◆ readRegionTo()

template<typename T , long m, long n>

void Euclid::Fits::ImageRaster::readRegionTo	(	FileMemRegions< n >	regions,
		Raster< T, m > &	raster
	)		const

Read a region of the data unit into a region of an existing Raster.

Template Parameters

T	The desired raster type
m	The desired raster dimension, which can be smaller than the data dimension in file
n	The region dimension, which corresponds to the data dimension in file

Parameters

region	The in-file region
regions	The in-file and in-memory regions
raster	The destination raster

There are several options to read a region of the data unit:

as a new VecRaster object;
by filling an existing Raster object;
by filling an existing Subraster object. In the last two cases, the in-file and in-memory regions are given as a FileMemRegions object.

For example, to read the HDU region from position (50, 80) to position (100, 120) into an existing raster at position (25, 40), do:

const FileMemRegions<2> regions({ 25, 40 }, { { 50, 80 }, { 100, 120 } });

image.readRegionTo(regions, raster);

where image is the ImageRaster and raster is the Raster.

In simpler cases, where the in-file or in-memory front position is 0, factories can be used, e.g. to read into position 0 of the raster:

image.readRegionTo<2>({ { 50, 80 }, { 100, 120 } }, raster);