Grey, screen and printing colours

The same blue is three different things depending on where the document is going: three numbers for a screen, four inks for a press, and a single figure if the page will only ever be printed in grey. Choose the wrong one and nothing warns you — the document looks right on the screen you chose it on, and comes back from the printing works a different colour.

The bottom row is the interesting one: one mid-grey said three ways. The same ink on paper, three different sets of numbers in the file. Which of the three a document should use depends on where it is going, not on how it looks on the screen you are reading it on.

What this example shows

  • Greyscale, RGB and CMYK swatches on one page.
  • Each swatch captioned with the instruction written for it.
  • One grey said all three ways, for comparison.

The source code, complete

Nothing is left out and nothing is simplified: this is the program exactly as it runs, for the developer who uses this library. The third is the description itself: a plain list of what the page has to say, which is what the service is sent.

Read the Rust source Read the Python source Read the JSON source

The document itself

Open the document in English Open the document in French

Grey, screen and printing colours, first page

Optimised, this document weighs 12.5 kB — at least 85 % lighter than most PDF generators would write it

The document is lighter than it was, and every page still looks exactly the same. See this document's row in the table of every example.

Examples near this one

Colour the document defines

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.

Several plates at once, each at its own strength

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 colour chart the drawing points into

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 hatch, laid down in any colour you like

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.

A sheet as it goes to the press

One drawing on three pages: a press sheet stating where the ink runs, where the blade falls and what is worth keeping, with trim marks; the same sheet cropped to the finished page; and a landscape page that states a quarter turn clockwise on an upright sheet.

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