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An approachable image processing library primarily based upon Vix and libvips that is NIF-based, fast, multi-threaded, pipelined and has a low memory footprint.
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lib/image/complex.ex
defmodule Image.Complex do
@moduledoc false
# See http://libvips.blogspot.com/2015/11/fancy-transforms.html
alias Vix.Vips.Image, as: Vimage
alias Vix.Vips.Operation
defguard complex(format) when format in [:VIPS_FORMAT_COMPLEX, :VIPS_FORMAT_DPCOMPLEX]
defguard float_format(format) when format in [:VIPS_FORMAT_FLOAT, :VIPS_FORMAT_DOUBLE]
defguard even(bands) when rem(bands, 2) === 0
def polar(%Vimage{} = image) do
complex(image, &Operation.complex(&1, :VIPS_OPERATION_COMPLEX_POLAR))
end
def rectangular(%Vimage{} = image) do
complex(image, &Operation.complex(&1, :VIPS_OPERATION_COMPLEX_RECT))
end
def rectangular!(%Vimage{} = image) do
case rectangular(image) do
{:ok, image} -> image
{:error, reason} -> raise Image.Error, reason
end
end
defp complex(%Vimage{} = image, fun) do
bands = Vimage.bands(image)
original_format = Vimage.format(image)
with {:ok, image} <- to_complex(image, original_format, bands),
{:ok, image} <- fun.(image) do
new_format = Vimage.format(image)
from_complex(image, original_format, new_format, bands)
end
end
# Convert to complex
defp to_complex(%Vimage{} = _image, format, bands)
when not complex(format) and not even(bands) do
{:error, "Not an even number of bands. Found: #{inspect(bands)}"}
end
# If its already complex, return it
defp to_complex(%Vimage{} = image, format, _bands) when complex(format) do
{:ok, image}
end
defp to_complex(%Vimage{} = image, :VIPS_FORMAT_FLOAT, bands) do
Operation.copy(image, format: :VIPS_FORMAT_COMPLEX, bands: div(bands, 2))
end
defp to_complex(%Vimage{} = image, :VIPS_FORMAT_DOUBLE, bands) do
Operation.copy(image, format: :VIPS_FORMAT_DPCOMPLEX, bands: div(bands, 2))
end
defp to_complex(%Vimage{} = image, _format, bands) do
{:ok, image} = Operation.cast(image, :VIPS_FORMAT_FLOAT)
to_complex(image, Vimage.format(image), bands)
end
# Convert from complex
defp from_complex(image, original_format, :VIPS_FORMAT_DPCOMPLEX, bands)
when not complex(original_format) do
Operation.copy(image, format: :VIPS_FORMAT_DOUBLE, bands: bands)
end
defp from_complex(image, original_format, _new_format, bands)
when not complex(original_format) do
Operation.copy(image, format: :VIPS_FORMAT_FLOAT, bands: bands)
end
defp from_complex(image, _original_format, _format, _bands) do
{:ok, image}
end
end