| 摘要 |
A document that resists copying by ordinary color copiers and color scanners. An area that is printed with color dots using a gradient print screen that exceeds resolutions available on commonly available color copiers and color scanners. The area may therefore comprise lighter regions (having fewer screen lines per inch) and darker regions (having more screen lines per inch). Multiple colors may be printed with different gradient print screens, and regions which are darker or lighter for a first color may or may not be darker or lighter for a second color. The document may also comprise a second area that is printed with a moir+E,acu e+EE pattern. The moir+E,acu e+EE pattern may be generated by adjusting an angle between a pair of print screens, such as a pair of gradient print screens. A set of colors for printing may avoid common printing ink colors, may prefer yellow, light green, or light blue, and may avoid red, purple, or violet, to raise the difficulty in copying by color copiers or color scanners. A top layer of the area may be covered with a layer of matte varnish or transparent white ink.
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