Class: RFits::Image

Inherits:
HDU
  • Object
show all
Includes:
Compressible
Defined in:
lib/rfits/rfits.rb

Overview

An Image HDU.

Constant Summary collapse

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
}

Constants included from Compressible

Compressible::COMPRESSION_DIM_KEY, Compressible::COMPRESSION_NOISE_BIT_NAME_VALUE, Compressible::COMPRESSION_SCALE_NAME_VALUE, Compressible::COMPRESSION_SMOOTH_NAME_VALUE, Compressible::COMPRESSION_TILE_KEY_ROOT, Compressible::COMPRESSION_TYPE_KEY, Compressible::COMPRESSION_TYPE_MAP, Compressible::COMPRESSION_VAR_KEY_ROOT, Compressible::COMPRESSION_VAR_VAL_ROOT

Constants inherited from HDU

HDU::HDU_TYPE_MAP

Instance Attribute Summary collapse

Attributes inherited from HDU

#data, #file, #header

Instance Method Summary collapse

Methods included from Compressible

#activate_compression, #compression_type, #compression_type=, #deactivate_compression, #hcomp_scale, #hcomp_scale=, #hcomp_smooth, #hcomp_smooth=, #noise_bits, #noise_bits=, #tile_dim, #tile_dim=

Methods inherited from HDU

#hdu_type, #position, #reset_position

Constructor Details

#initialize(file, extpos, bitpix, naxes, coptions = nil) ⇒ Image

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 not fits. 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.



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# File 'lib/rfits/rfits.rb', line 980

def initialize(file, extpos, bitpix, naxes, coptions=nil)
  super(file, extpos)
  
  @bitpix = bitpix
  @naxes = naxes
  
  @compression_options = coptions
end

Instance Attribute Details

#compression_options ⇒ Object (readonly)

Returns the value of attribute compression_options.



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# File 'lib/rfits/rfits.rb', line 960

def compression_options
  @compression_options
end

Instance Method Details

#bitpix(equiv = true) ⇒ Object

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



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# File 'lib/rfits/rfits.rb', line 1044

def bitpix(equiv=true)
  reset_position()
  equiv ? IO::Proxy.fits_get_img_equivtype(self.file.io) : IO::Proxy.fits_get_img_type(self.file.io)
end

#bitpix=(bitpix) ⇒ Object

Alter the datatype of the image.

img.bitpix = IO::Proxy::LONG_IMG



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# File 'lib/rfits/rfits.rb', line 1051

def bitpix=(bitpix)
  reset_position()
  IO::Proxy.fits_resize_img(self.file.io, bitpix, self.naxis, self.naxes)
end

#compressed? ⇒ Boolean

Returns true if the image is compressed, false otherwise.

Returns:

  • (Boolean) 


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# File 'lib/rfits/rfits.rb', line 1064

def compressed?
  reset_position()
  IO::Proxy.fits_is_compressed_image(self.file.io) == 1 ? true : false
end

#create(at) ⇒ Object

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



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# File 'lib/rfits/rfits.rb', line 991

def create(at)
  self.deactivate_compression
  
  # A dummy image gets added if to the top of the file if
  # the first image added is compressed.
  @extpos = (self.file.length == 0 and self.compression_options) ? at + 1 : at
  
  self.file.set_position(at - 1 < 0 ? 0 : at - 1)
  self.activate_compression() if self.compression_options
  IO::Proxy.fits_insert_img(self.file.io, @bitpix, @naxes.size, @naxes)

  # This just makes sure something is written out right away.
  self.header['RFITS1234'] = 'temp'
  self.header.delete('RFITS1234')
end

#dim ⇒ Object

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



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# File 'lib/rfits/rfits.rb', line 1013

def dim
  reset_position()
  IO::Proxy.fits_get_img_dim(self.file.io)
end

#image_type ⇒ Object

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



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# File 'lib/rfits/rfits.rb', line 1037

def image_type
  reset_position()
  etype = IO::Proxy.fits_get_img_equivtype(self.file.io)
  IMG_TYPE_MAP[etype] || etype
end

#naxes ⇒ Object

Alias for Image#size



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# File 'lib/rfits/rfits.rb', line 1025

def naxes
  self.size
end

#naxes=(naxes) ⇒ Object

Alter image dimensions to the specified size.

img.naxes = [1000, 200]



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# File 'lib/rfits/rfits.rb', line 1031

def naxes=(naxes)
  reset_position()
  IO::Proxy.fits_resize_img(self.file.io, self.bitpix, naxes.size, naxes)
end

#naxis ⇒ Object

Alias for Image#dim



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# File 'lib/rfits/rfits.rb', line 1008

def naxis
  self.dim
end

#resize(bitpix, naxes) ⇒ Object

Resize the image to the specified dimensions and data type.

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



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# File 'lib/rfits/rfits.rb', line 1058

def resize(bitpix, naxes)
  reset_position()
  IO::Proxy.fits_resize_img(self.file.io, bitpix, naxes.size, naxes)
end

#size ⇒ Object

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



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# File 'lib/rfits/rfits.rb', line 1019

def size
  reset_position()
  IO::Proxy.fits_get_img_size(self.file.io, self.naxis)
end