Some settings in a PDF change nothing on a screen. They are there for the printer: whether a colour printed over another hides it or mixes with it, the shape each dot of ink takes as a grey gets darker, how a tone is bent before it reaches the paper. A proofing tool or a check before printing reads them; a screen does not. Here each of those settings is used on a swatch of its own, and each swatch is labelled with what it asks for.
Overprinting comes first, a yellow square over a cyan bar. Then the twenty-one shapes a halftone dot can take, and one screen set ink by ink; tone curves for every ink at once and for each ink apart; the four ways a colour can be converted from one set of inks to another, with and without black point compensation; and how finely curves and shadings are approximated. A last swatch puts every setting back as it was.
Nothing is left out and nothing is simplified: this is the program exactly as it runs, for the developer who uses this library.
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Swatches in each of the three ways to say a colour — a grey as one number, a screen colour as three, a printing colour as four inks — each captioned with the instruction actually written into the file, and one mid-grey said four ways, the last as the hexadecimal code a screen designer hands over.
The same six colours said as bare numbers and then read through the screen profile the file carries, plus a ramp from light to dark and a sweep of measured hues: colour that still means the same thing on another screen and on a press.
Two inks the press carries on a plate of their own, each at ten strengths, a piece of work set in both, and the alignment crosses used to line the plates up — drawn in an ink every plate answers to.
Eight choices of plate among the four usual inks, each with the small program that shows it printed underneath, and two inks the press carries itself used together, every strength of one against every strength of the other.
A chart of house colours the file carries, and a drawing whose sixteen numbers are places in that chart rather than colours. The same drawing is shown twice through two charts: repainting a whole brand is one chart, not every drawing.
One pattern that states no colour of its own, laid down in five colours and in five strengths of one press ink: the fill says what colour to lay it down in. Beside them, the same hatch made of patterns that carry their own colours, which is one pattern per colour.