Browse Prior Art Database

Shading for Matrix Display

IP.com Disclosure Number: IPCOM000083060D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Alberga, CN: AUTHOR

Abstract

An algorithm for simulating a grey-scale shading on an ON/OFF matrix display is presented. Given grey-scale values in the range 0-1 for the points to be displayed, d. being the value at the (I,J) point, a shading can be produced by generating a pseudorandom number between 0 and 1 and displaying the point if the number is less than d... The result is unpleasingly uneven. The present algorithm with two variations, provides a more satisfactory result, with fewer multiplications than the random choice.

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Shading for Matrix Display

An algorithm for simulating a grey-scale shading on an ON/OFF matrix display is presented. Given grey-scale values in the range 0-1 for the points to be displayed, d. being the value at the (I,J) point, a shading can be produced by generating a pseudorandom number between 0 and 1 and displaying the point if the number is less than d... The result is unpleasingly uneven. The present algorithm with two variations, provides a more satisfactory result, with fewer multiplications than the random choice.

Mathematically, let rho(x) be the grey-scale density function for a strip (horizontal or vertical line) across the display, then:

The initial rho function is of the form:

(Image Omitted)

Assuming an artificial element u(o)=0, mark the ith point in the display line in u(i-1) does not = u(i). The following flow chart gives an iterative form of the algorithm.

For constant densities, or for successive identical V's, this results in solid, parallel lines. If this is not desirable, more pleasing effects can be obtained by:

1) Initializing CUM (in the flow chart) by a pseudorandom number between 0 and 1, rather than by 0.

2) Adding a pseudorandom number between -0.5 and 0.5 to each kth element of V.

This has the effect of dividing the display into strips at right angles to the lines and independently randomizing them.

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