Seshat 1.9.1 lowers ink the way print does, and shows where it is too heavy

Taking ink out of a file should not change how it looks. Seshat 1.9.1 lowers total ink the way print professionals do, and shows the customer exactly where the ink was too heavy.

Ink that keeps its colour

Where cyan, magenta and yellow all print, together they make grey, and black can print that grey instead. This is grey component replacement. Seshat looks up through the file's own print profile how each heavy colour looks, and finds the separation of that profile that looks the same with less ink. Among separations that look equally right, it picks the one closest to the original.

• Colours keep their look. Colours, gradients and CMYK pictures over the limit keep their appearance, often with far less ink than the limit asks for. In our tests on deep shadows, colours moved about half as much as with simply lowering cyan, magenta and yellow, with up to 30 % less ink.
• Never worse than the simple way. For every colour, Seshat also works out the earlier way and keeps whichever looks closer to the original.
• You see how far colours moved. The answer says it as colour_change_de, the colour difference the eye sees; about 2 is where most people start to notice.
• The earlier way stays available with method: lower.

A heat map of the total ink

Send max_ink with plates, and the answer also has a heat map. The page is shown in grey, amber where the total ink is over the limit, and red where it is far over. It is measured exactly as the check measures it: the process inks, averaged over 15 mm. A customer sees at a glance where to change the design.

Also in this version

When Seshat compared two print profiles to decide whether CMYK is made for the same press, it read part of the colour values wrongly at the extremes. The decisions it made were right, and now the numbers behind them are too.

The packages for Laravel and Node.js (0.11.0) take the new option for plates and the method for reduce_ink.