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Jeremy Singer-Vine
42 lines
1.8 KiB
Markdown
42 lines
1.8 KiB
Markdown
# Colors
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In the PDF specification, as well as in `pdfplumber`, most graphical objects can have two color attributes:
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- `stroking_color`: The color of the object's outline
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- `non_stroking_color`: The color of the object's interior, or "fill"
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In the PDF specification, colors have both a "color space" and a "color value".
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## Color Spaces
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Valid color spaces are grouped into three categories:
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- Device color spaces
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- `DeviceGray`
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- `DeviceRGB`
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- `DeviceCMYK`
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- CIE-based color spaces
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- `CalGray`
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- `CalRGB`
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- `Lab`
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- `ICCBased`
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- Special color spaces
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- `Indexed`
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- `Pattern`
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- `Separation`
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- `DeviceN`
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To read more about the differences between those color spaces, see section 4.5 [here](https://ghostscript.com/~robin/pdf_reference17.pdf).
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`pdfplumber` aims to expose those color spaces as `scs` (stroking color space) and `ncs` (non-stroking color space), represented as a __string__.
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__Caveat__: The only information `pdfplumber` can __currently__ expose is the non-stroking color space for `char` objects. The rest (stroking color space for `char` objects and either color space for the other types of objects) will require a pull request to `pdfminer.six`.
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## Color Values
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The color value determines *what specific color* in the color space should be used. With the exception of the "special color spaces," these color values are specified as a series of numbers. For `DeviceRGB`, for example, the color values are three numbers, representing the intensities of red, green, and blue.
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In `pdfplumber`, those color values are exposed as `stroking_color` and `non_stroking_color`, represented as a __tuple of numbers__.
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The pattern specified by the `Pattern` color space is exposed via the `non_stroking_pattern` and `stroking_pattern` attributes.
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