Returns the colour space a value names in the running content stream.
public PdfColorSpace GetColorSpace(CosObject colorSpace)
A name, as the operand of CS and cs (DeviceGray, DeviceRGB, DeviceCMYK and Pattern name those spaces; any other
name is looked up in the ColorSpace subdictionary of Resources), or a colour space array.
ISO 32000-2 §8.6.8, Table 73; §7.8.3.