What is a Raster Image Processor?

Raster image processor, referred to as RIP for short, usually refers to a processor or processing software that converts PS files into raster dot matrix data after interpretation operations. It is an important software or device for the printing industry. All output devices such as printers or imagesetters need a RIP to drive them.

RIP consists of two parts: an explanation part and a control part. The interpreter receives the page information from the computer and encodes it for use by the control section; the control section is used to control the operation of the imaging system.

The most important part of RIP is the interpretation part. It first translates the instructions of the page description language into a "display list". All calculation objects in the page are buffered in a uniform format. The second step is to convert the objects of the "display list" through the restoration module according to the resolution unique to the output device. Such as smooth text edges with step-shaped transitions. Subsequently, the rasterization module is used to segment the obtained continuous tone image into halftone dots and convert it into the original data format (mostly a bitmap format) of the output device. ^[1]

(1) PostScript compatibility .

The working mode of hardware RIP is generally simple, usually using network printing, without preview function; while software RIP is more flexible in receiving page data, there is a network printing method, and it can also directly explain the PS file formed by the group software. PS files can be interpreted in a batch process.

(1) The so-called network printing method refers to setting RIP as a network printer, which can be selected on each workstation according to the selection.

RIP is generally divided into two types: hardware RIP and software RIP , and there are also software and hardware combined RIP.

The hardware RIP is actually a dedicated computer that is used to interpret the information on the page. Because the calculation of page interpretation and screening is very large, hardware RIP is usually used to increase the calculation speed in the past.

The software RIP is used to calculate the page by software. The interpreted record information is transmitted to the imagesetter through a specific interface card. Therefore, the software RIP must be installed on a computer. At present, the computing speed of computers has been significantly improved, and the RIP interpretation algorithm and screening algorithm have also been continuously improved, so the interpretation speed of software RIP no longer lags behind or even exceeds that of hardware RIP. Software RIP is easy to upgrade and can increase with the increase of computer computing speed, so it is more and more popular with users. ^[3]

From the perspective of the development process, the role of RIP was originally limited to three aspects: explaining the page description language (general PostScript) from the application; generating a display list of objects on the page; rasterizing or converting data into Dots and generate a bitmap, which will tell the output device how to place the dots.

Today's RIP is not only the original interpreter, other processing such as trapping, layout, preview, pre-ellipse, screening, rasterization, imaging, etc. have been included in the function of RIP. ^[4]