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https://github.com/philomena-dev/philomena.git
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69 lines
2.1 KiB
Elixir
69 lines
2.1 KiB
Elixir
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defmodule PhilomenaMedia.Intensities do
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@moduledoc """
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Corner intensities are a simple mechanism for automatic image deduplication,
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designed for a time when computer vision was an expensive technology and
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resources were scarce.
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Each image is divided into quadrants; image with odd numbers of pixels
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on either dimension overlap quadrants by one pixel. The luma (brightness)
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value corresponding each the pixel is computed according to BTU.709 primaries,
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and its value is added to a sum for each quadrant. Finally, the value is divided
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by the number of pixels in the quadrant to produce an average. The minimum luma
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value of any pixel is 0, and the maximum is 255, so an average will be between
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these values. Transparent pixels are composited on black before processing.
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By using a range search in the database, this produces a reverse image search which
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suffers no dimensionality issues, is exceptionally fast to evaluate, and is independent
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of image dimensions, with poor precision and a poor-to-fair accuracy.
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"""
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@type t :: %__MODULE__{
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nw: float(),
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ne: float(),
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sw: float(),
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se: float()
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}
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defstruct nw: 0.0,
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ne: 0.0,
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sw: 0.0,
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se: 0.0
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@doc """
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Gets the corner intensities of the given image file.
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The image file must be in the PNG or JPEG format.
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> #### Info {: .info}
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>
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> Clients should prefer to use `m:PhilomenaMedia.Processors.intensities/2`, as it handles
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> media files of any type supported by this library, not just PNG or JPEG.
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## Examples
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iex> Intensities.file("image.png")
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{:ok, %Intensities{nw: 111.689148, ne: 116.228048, sw: 93.268433, se: 104.630064}}
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iex> Intensities.file("nonexistent.jpg")
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:error
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"""
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@spec file(Path.t()) :: {:ok, t()} | :error
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def file(input) do
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System.cmd("image-intensities", [input])
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|> case do
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{output, 0} ->
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[nw, ne, sw, se] =
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output
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|> String.trim()
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|> String.split("\t")
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|> Enum.map(&String.to_float/1)
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{:ok, %__MODULE__{nw: nw, ne: ne, sw: sw, se: se}}
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_error ->
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:error
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end
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end
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end
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