![]() This has created a greater depth of colour, range of tone and improved contrast.Ĭontemporary screening is hardware and raster image process (RIP) dependent. ![]() Extra colours have been added to the process colour range, including orange and green. Also, due to the removal of screen angles formerly preventing moiré effects, the stochastic system enables more than four colours to be printed. Therefore, more dots can be placed in a specific area in order to achieve a greater concentration of colour. Unlike the traditional halftone system, the process employs no fixed grid or screen angles and the size of the dots and spacing between the dots is variable. In printing, it is a method that applies the placement of a more random dot frequency modulated (FM) screening. The term stochastic is derived from the Greek word Stokastikos, meaning to predict or guess, and is used in mathematics to analyse and predict the movement of particles through liquid. Stochastic technology can be considered as the beginning of a mechanical simulation of 19th century continuous tone. This is also known as a clustered halftone dot. The dots are placed at a fixed frequency, with lesser or more dots corresponding to the required level of grey. The conventional method of halftone screening is a method that employs a regular pattern of dots in straight rows or amplitude modulation (AM) screening. The last 15 years have witnessed the breakthrough into the desktop market and, more recently, the industrial and commercial products have developed to super-wide format and web-fed printing machines, where quantity is measured in metres per second. Continuous inkjet has been in use since the 1960s, and drop-on-demand since the 1970s. The following sections provide an introduction to early halftoning methods, the development of stochastic halftoning screening and an overview of current inkjet technology. Parraman, in Colour Design, 2012 18.3 An overview of halftoning and digital print technologies Note that the contrast and security conditions are maintained with global optimization as shown in Figs. 9A and 9B, but more significant gains in visual quality are obtained in nonkey complementary shares as shown in Figs. The key complementary pair is deteriorated somewhat as shown in Figs. Performing global optimization leads to the results shown in Fig. The visually pleasing results obtained on the key complementary pair, shares 1 and 2, are apparent while the other shares contain white noise characteristics. Superimposing a forbidden subset of shares gains no secret information, such as the superposition of shares 1 and 2 shown in Fig. 8E, which is the output of stacking shares 1, 2 and 3. The secret image can be decoded by superimposing a qualified subset of shares, such as Fig. The obtained four shares are shown in Figs. When you click on the canvas, the large star will disappear-no need for concern.The halftone visual SS scheme of Γ 0 = discussed in Example 3.1 is implemented in this section. Repeat this process for the large star, removing its stroke but this time setting the fill color to white (RGB R=255, G=255, B=255). Now bring the fill square forward and set the fill color to a dark grey (for example, enter an RGB value of R=77, G=77, B=77). ![]() Select the small star, bring the stroke square forward (if necessary) and then remove the stroke by clicking the white box with the red line through it, found in the bottom left of the color panel. Clicking either square brings it to the front, allowing you to change the color of that attribute. You’ll see two boxes in the top left, which represent the color of the fill (the solid square) and the stroke (the square with the square hole in it). Choose Window -> Color to call up the fill and stroke color panel. Now you’ll need to set to color for each star. You’ll see a small star sitting atop the original large one. Click Uniform, enter 25% and then click OK. A Scale window appears, allowing you to precisely scale the object you’ve just pasted. This pastes a copy of the star on top of the existing star, and for the moment, it’ll look as though there is still only one star on your canvas. Select the star and then choose File -> Copy, followed by File -> Paste in Place. Enter Radius 1: 800, Radius 2: 420 and Points: 5, and then click OK.) (Or, choose the Star Tool and click the center of the canvas. This can be accomplished in a number of ways-standard gradients, gradient meshes and blends-but for now, let’s create a blend with a star-shaped object.Ĭhoose the Star Tool from the toolbar-you’ll find it in the same place as the Rectangle Tool-and create a star shape that fills most of the document. ![]() ![]() You’ll now need to create a simple object with a greyscale gradient. Setting a relatively high resolution for the document’s raster effects allows you to get better results when tracing your halftone. ![]()
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