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Abstract. Inkjet and laser printers, and photocopiers are being increasingly used in criminal activities such as counterfeiting currency, creating forged documents, illegitimate business transactions and terrorism related acts. Identification of the printing process greatly aids in detecting such activities and is extensively used in the field of document examination. In this paper, we propose the use of image processing techniques in identifying the printing process used to generate a document. The characteristics of the various types of non-impact printing methods used by photocopiers, inkjet and laser printers are studied using colour image processing. HSV color space and, in particular, hue images at highresolution, distribution of isolated spots in the vicinity of hue edge pixels and periodicities in edge intensity profiles distinguish between the different printing processes. Our initial study indicates their promise in replicating the results traditionally obtained by document examiners using a microscope or through chemical analysis.

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Analysis of inks on Questioned documents is often required in the field of document examination. This paper provides a novel approach for ink type recognition for black inks. Ink types Liquid ink or Viscous ink will be derived from the colour properties of ink, by extracting its amount of blackness. This classification helps in distinguishing Gel and Roller pens versus Ball pens. Different types of inks exhibit different absorption characteristics that causes colour and distribution of colour pixels to change. We observed that the RGB colour space is useful to reveal the differences in ink types. We used multiple linear regression to model the RGB data points of the writings to a plane. The distance from the origin (pure black) to that plane is calculated to classify inks i.e. liquid inks and viscous inks. The distance measures in RGB and HSV colour spaces are used to identify the particular ink. The accuracy of identification is analysed using Type I and Type II errors.