IFDs should be preserved verbatim when reading images

[chrstphrbrns]

Currently, IFDs are altered when an image is read, but this is surprising and not ideal

[tlnagy]

What do you mean they are altered?

[chrstphrbrns]

The DenseTaggedImage constructor modifies them, or at least rewrites them (which leaves the possibility that they'd be modified)

[tlnagy]

Are you referring to _constructifds being called from the constructor?

TiffImages.jl/src/types/dense.jl

Lines 135 to 147 in ee4852f

	ifd[IMAGEWIDTH] = UInt32(size(data, 2))
	ifd[IMAGELENGTH] = UInt32(size(data, 1))
	n_samples = samplesperpixel(data)
	ifd[BITSPERSAMPLE] = fill(UInt16(bitspersample(data)), n_samples)
	ifd[PHOTOMETRIC] = interpretation(data)
	ifd[SAMPLESPERPIXEL] = UInt16(n_samples)
	if !(T <: Gray{Bool}) # bilevel images don't have the sampleformat tag
	ifd[SAMPLEFORMAT] = fill(UInt16(sampleformat(data)), n_samples)
	end
	extra = extrasamples(data)
	if extra !== nothing
	ifd[EXTRASAMPLES] = extra
	end