Modelling of normalized raster transformation for round elements

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Lutskiv M. M., Гунько Д. Т. № 2 (80) 29-37 Image Image

A model of normalized raster transformation for round elements is developed and a block diagram of the model is constructed, which allows one to calculate and build the characteristics of normalized raster transformation, on the basis of which it is possible to build rasterization characteristics for different raster lines by scaling, which is convenient for practical applications. The results of simulation modelling are presented, the rasterization characteristics are constructed and their properties are analysed. The characteristic of rasterization for a ruler of 100 lines/cm in percent is presented. The characteristic is an S-shaped curve, which is noticeable at the beginning of the transmission range, and convex curves at the end. To objectively quantify the raster transformation, it is suggested to determine the deviation of the characteristic from the linear one. The graph of the deviation of the characteristic from the linearity given in percent is a U-shaped curve. It is established that the characteristics are U-shaped curves, and the maximum deviation from linearity is in the range from -15.9% to +11.7%, which requires the adjustment. Since the relative cloak of the raster element corresponds to the density of the image, the midtones will lighten the image and the grayscale will darken the image compared to the original. Therefore, raster transformation causes the tone distortion, so it must be adjusted at the stage of preparing the image for printing.

Keywords: raster transformation, normalization, raster point, modelling, charac­te­ristics, nonlinearity, deviation, quality.

doi: 10.32403/0554-4866-2020-2-80-29-37

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