Class RFits::Image
In: lib/rfits/rfits.rb
Parent: HDU

An Image HDU.

Methods

bitpix   bitpix=   compressed?   create   dim   image_type   naxes   naxes=   naxis   new   resize   size  

Included Modules

Compressible

Constants

IMG_TYPE_MAP = { IO::Proxy::BYTE_IMG => :byte, IO::Proxy::SHORT_IMG => :short, IO::Proxy::LONG_IMG => :long, IO::Proxy::LONGLONG_IMG => :longlong, IO::Proxy::FLOAT_IMG => :float, IO::Proxy::DOUBLE_IMG => :double

Attributes

compression_options  [R] 

Public Class methods

new(file, extpos, bitpix, naxes, coptions=nil)

Instantiate a new image in the specified file at the specified position, of a certain data type and size. "coptions" is optional, but if present see Compressible#activate_compression for allowed format.

If you do activate compression for an image there is one "gotcha" that might take you by surprise: if there are no existing HDUs in the file and you add a compressed image, an extra image HDU at the start of the file will be created. In other words, your new compressed image will be at fits[1] not fits[0]. This is because cfitsio compresses the image by wrapping it in a binary table, but the FITS specification mandates that the primary HDU must always be an image array.

Public Instance methods

bitpix(equiv=true)

Number of bits per data pixel. By default returns the "equivalent type" unless equiv is set to false.

bitpix=(bitpix)

Alter the datatype of the image. 

 img.bitpix = IO::Proxy::LONG_IMG
compressed?()

Returns true if the image is compressed, false otherwise.

create(at)

Actually create a physical image (i.e. write bytes). "at" is the position at which to insert the image.

dim()

The number of dimensions of the image (i.e. 2).

image_type()

The type of image. Possibilities include: :byte, :short, :long, :longlong, :float, :double

naxes=(naxes)

Alter image dimensions to the specified size. 

 img.naxes = [1000, 200]
resize(bitpix, naxes)

Resize the image to the specified dimensions and data type. 

 img.resize(IO::Proxy::LONG_IMG, [1000, 200])
size()

The size of each dimension (i.e. [512, 512]).

[Validate]