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Colors

In the PDF specification, as well as in pdfplumber, most graphical objects can have two color attributes:

  • stroking_color: The color of the object's outline
  • non_stroking_color: The color of the object's interior, or "fill"

In the PDF specification, colors have both a "color space" and a "color value".

Color Spaces

Valid color spaces are grouped into three categories:

  • Device color spaces
    • DeviceGray
    • DeviceRGB
    • DeviceCMYK
  • CIE-based color spaces
    • CalGray
    • CalRGB
    • Lab
    • ICCBased
  • Special color spaces
    • Indexed
    • Pattern
    • Separation
    • DeviceN

To read more about the differences between those color spaces, see section 4.5 here.

pdfplumber aims to expose those color spaces as scs (stroking color space) and ncs (non-stroking color space), represented as a string.

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.

Color Values

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.

In pdfplumber, those color values are exposed as stroking_color and non_stroking_color, represented as a tuple of numbers.

The pattern specified by the Pattern color space is exposed via the non_stroking_pattern and stroking_pattern attributes.