A printing plate for flexographic print production is created by turning a laser on and off at a slightly lower resolution. If the image fills a typical sheet-fed press, it is (30 inches x 3,000 lspi) x (40 inches x 3,000 lspi) = 1.08 trillion, which takes 10 gigabytes of computer memory to store and transfer. The RIP calculates all the spots that must be turned ‘on’ to create the graphic that will be imaged on the printing plate. Most plate-setters have a resolution of 2,000 to 3,000 lspi (laser spots per inch). With computer-to-plate technology for lithographic printing plate production, a laser is used to expose an emulsion on a printing plate. The grid then acts as a switch to turn a mechanical part of the imaging engine on or off. The spots on the grid can only be turned on or off - which is how binary data is encoded - either as 0 or 1. The RIP has a matrix grid at the resolution of the output device and computes which spots on the grid get turned on and which are turned off to create the shape of that letter A on the output device. A font file delivers PostScript language to the RIP that describes a series of points and vector curves between those points to outline the letter A. Let’s examine the creation of a single character of the alphabet, or glyph. The raster image processor (RIP) is the core technology that does the computational work to convert the broad range of data we use to create a computer graphic into the one-bit data that drives a physical imaging device.
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