Video signal processing with added probabilistic dither

• US 5,175,807 A
• Filed: 06/07/1991
• Issued: 12/29/1992
• Est. Priority Date: 12/04/1986
• Status: Expired due to Term

• Current Assignee: Quantel Limited (Belden Inc.)
• Original Assignee: Quantel Limited (Belden Inc.)
• Inventors: Long, Robert, Stapleton, Alan L., Cawley, Robin A., Hinson, Neil R.
• Primary Examiner(s): SALATA, ANTHONY J
• Application Number:
  US07/715,308
• Time in Patent Office: 571 Days
• Field of Search: 364/521, 364/522, 364/518, 340/702, 340/720, 340/723, 340/726, 340/729, 340/728, 340/730, 358/75, 358/80, 358/29, 358/64, 358/163, 358/316, 358/318, 358/334, 358/10, 358/13, 358/17, 395/109, 395/128, 395/131
• US Class Current: 345/428
• CPC Class Codes: G06F 3/04845 for image manipulation, e.g. dragging, rotation, expansion or change of colour
• CPC Class Codes: H04N 1/46 Colour picture communication systems
• CPC Class Codes: H04N 9/74 for obtaining special effects H04N9/65 - H04N9/73 take precedence

Abstract

A system in which a characteristic of individual picture points is provided to an accuracy of m binary bits but conveyed by n bits, where n is less than m. The value of a lower order bit of the n bit signal is switched to cause said binary value to represent, for any one picture point, either a value above or a value below the original value. The new values are distributed without order among the picture points with a probability dependent upon the value of the (m-n) lowest order bits of the desired value.

Claims

1. A video signal processing system comprising a source providing a desired value for a characteristic of individual picture points to an accuracy of "m" or more binary bits, and a circuit deriving from said value in the case of each of said picture points an n-bit binary signal, where (m-n) is an integer greater than 1, wherein the value of said n-bit binary signal within the range of a lower order bit is switched to cause said n-bit binary signal to represent, for any one picture point, either a value above or a value below said desired value, said one value or said other value being distributed without order among said picture points and the probability of said one value or said other value being present for any one picture point being dependent upon the value of the (m-n) lowest order bits of the desired value.

6. A video processing system according to claim 1 in which said circuit comprises a random number generator and a comparator comparing, for each picture point, the value of the (m-n) lower order bits of the desired value with the output of said random number generator, said circuit switching the value of said n-bit binary signal within the value range of a lower order bit depending on whether the value of the (m-n) lower order bits of the desired value is above or below the output of the random number generator.

7. A video signal processing system according to claim 1 in which the value of the (n-m) lower order bits of the desired value for a particular picture point is derived from the position of the respective picture point relative to picture points of a reference color.

9. A system according to claim 1 including look-up table circuits causing the probability of said one value or said other value of said binary signal being present for any one picture point to be established by means of look-up tables.

10. A system according to claim 9, in which a series of look-up tables is provided, one for each of a number of picture points, each look-up table comprising sequence of addresses, at the first of which a signal of value 1 may be found with low probability, at a second of which a signal of value 1 may be found with higher probability and so on for (m-n) addresses.

11. A video signal processing system according to claim 6, in which said circuit derives the value of the (n-m) lower order bits of the desired value for a particular picture point from the position of the respective picture point relative to picture points of a reference color.

2. An effects generator for a graphic system comprising:

means for generating a line of signals for representing a first color, means for generating a line of signals for representing a second color, and means for generating intervening lines of the signal, said intervening lines separating said lines representing said first color and said second color and each of said intervening lines being generated as signals of only said first color and said second color which are interspersed substantially randomly along the intervening line and are positioned at respective locations along the intervening line.

3. An effects generator for a graphic system comprising:

means for defining the colors of several lines of display separated by intervening lines, and means for generating each line in the form of signals representing a defined color or a mixture of two defined colors, including means for generating signals for each of said intervening display lines as signals of a first defined color and signals of a second defined color which are substantially randomly interspersed among the signals of the first defined color, the proportions of the first and second defined colors in a respective intervening line being dependent on the position of the respective intervening display line.

4. A graphic method for displaying a gradual change in a color intensity or characteristic across a band of the image, comprising producing the image in said band by interspersing two different signal elements representing two different values of said intensity or characteristic, said interspersing comprising varying the proportion of the two different signal elements from one line to another in said band gradually depending on the positions of the lines in the band while causing the distribution of the two different signal elements in each line to be substantially random or irregular to avoid or reduce dot patterning.

8. A graphic method according to claim 4 including the step of utilizing said signal elements to produce printing dots.

5. A video signal processing system comprising:

a first source of digital video signals;

a second source of digital video signals;

a source of factor signals K;

first multiplier means for multiplying a signal from said first source by the factor signal K;

second multiplier means for multiplying a signal from said second source by (1-K);

said first and second multiplier means each producing a main product signal and a remainder signal;

means for summing said remainder signals;

means for utilizing said summed remainder signals to select a random bit value;

said selection being weighted in accordance with a probability dependent on the sum of the remainder signals; and

means for summing said bit value and said main signals to produce an output signal wherein said output signal is utilized for at least temporarily one of displaying, televising, printing or transmitting.

12. A system comprising:

a source of m-bit signals;

a conversion circuit receiving said m-bit signals from said source and converting each received m-bit signal to a corresponding n-bit signal, wherein;

(i) the difference (m-n) is a positive integer greater than unity, and

(ii) the value of an n-bit signal is higher or lower than the value of the m-bit signal corresponding thereto depending on a probability related in value to the value of at least some of the least significant (m-n) bits of said corresponding m-bit signal; and

a device utilizing said n-bit signal for at least temporarily one of displaying, televising, printing or transmitting.

13. A system as in claim 12, in which said conversion circuit comprises a source of random signals each of which has a value which is substantially randomly selected within a range corresponding to the range of said (m-n) bits, and wherein the value of an n-bit signal is higher or lower than the value of the most significant n bits of the corresponding m-bit signal depending on the value of said least significant (m-n) bits of said corresponding m-bit signal relative to the value of a corresponding one of said random signals.

14. A system as in claim 13, including a random number generator which generates said random signals, a comparator which is coupled to the random number generator to receive said random signals therefrom and to said source to receive therefrom said least significant (m-n) bits of said m-bit signals and to compare each random signal with the least significant (m-n) bits of a corresponding m-bit signal and to generate a single bit which has a value of zero of unity depending on the result of the comparison carried out by said comparator, and an adder receiving the most significant n bits of said corresponding m-bit signal and adding thereto said single bit to thereby generate said corresponding n-bit signal.

15. A system as in claim 14, in which each of said m-bit signals is a signal defining a selected parameter of a picture element of a picture having a resolution of "n" bits per picture element.

16. A system as in claim 15, in which said picture comprises lines each comprising a multiplicity of picture elements, each of said m-bit signals defines a selected parameter of a corresponding picture element to a resolution greater than desired for at least one of displaying said picture and transmitting said picture, and each corresponding n-bit signal defines said parameter of the corresponding picture element to a resolution utilized for at least one of displaying and transmitting said picture.

17. A system as in claim 16, in which said selected parameter is one or more of the parameters selected from the group consisting of the intensity, color and size of a picture element of said picture.

18. A system for generating at least a portion of a color wedge comprising:

a source of the beginning and end colors of at least one portion of a color wedge, wherein said beginning and end colors are spatially separated by N video lines, where N is an integer greater than unity and each video line comprises a row of pixels;

a source of proportion signals defining a proportion of said beginning and/or end color for each of said N video lines, said proportion for each of said N lines depending on the position of the respective line;

a source of random numbers each of which is in a selected range;

a comparator which compares for each pixel of each of said N lines, a respective one of said random numbers with said proportion signal for the video line of the pixel and generates a comparison result signal;

a selection circuit which selects for each pixel of each of said N video lines either said beginning color or said end color depending on said comparison result signal, to thereby generate said N video lines such that in each line the relative numbers of pixels in said beginning and end colors are determined by said proportion signals but the beginning and end colors are distributed randomly in the line.

19. A system as in claim 18, in which each of said proportion signals is in the range between zero and unity and each of said random numbers is in a corresponding range.

20. A system as in claim 19, in which said random numbers are in the range of zero to unity.

21. A system comprising:

a source of a first picture which is defined at least in part by a respective n-bit signal for each picture element and of a second picture which also is defined at least in part by a respective n-bit signal for each picture element;

a blending circuit which receives corresponding n-bit signals for picture elements of each of the first and second pictures and blends each pair of corresponding n-bit signals to thereby generate m-bit signals defining a selected parameter of a respective blended element of a composite picture, wherein the difference (m-n) is a positive integer greater than unity;

a conversion circuit which converts each m-bit signal into an n-bit signal having a value determined at least in part upon a probabilistic function depending on information contained in the least significant m-n bits of said m-bit signal.

22. A system as in claim 21 in which said conversion circuit comprises an adder which adds one to the most significant m bits of each n-bit signal for a blended element depending on a probabilistic function of information contained in the least significant n-m bits.

23. A video signal processing system in which a desired value for a characteristic of individual picture points is provided to an accuracy of m or more binary bits, and said value in the case of each of said picture points is conveyed by an n-bit binary signal, where (m-n) is an integer greater than 1, characterized in that the value of said binary signal within the range of a lower order bit is switched to cause said binary signal to represent, for any one picture point, either a value above or a value below said desired value, said one value or said other value being distributed without order among said picture points and the probability of said one value or said other value being present for any one picture point being dependent upon the value of the (m-n) lowest order bits of the desired value, and further characterized in that the probability of said one value or said other value of said binary signal being present for any one picture point is established by means of look-up tables, in which a series of look-up tables is provided, one for each of a number of picture points, each look-up table comprising sequence of addresses, at the first of which a signal of value 1 may be found with low probability, at a second of which a signal of value 1 may be found with higher probability and so on for (m-n) addresses.

24. A system comprising:

a source of starting signals each represented by "m" bits comprising a most significant bit (MSB) which is followed by (m-1) bits of progressively decreasing significance the last of which is the m-th, least significant bit (LSB);

a conversion circuit which receives said starting signals and converts each to a corresponding converted signal represented by "n" bits comprising an MSB followed by (n-1) bits of progressively decreasing significance the last of which is an LSB where (m-n)>

(+1), and the LSB of each converted signal is determined in part on the basis of a probability related to the values of at least some of the bits following the n-th bit of the corresponding starting signal; and

a device utilizing said converted signals for at least temporarily one of displaying, televising, printing or transmitting.

25. A method comprising:

providing starting signals each represented by "m" bits comprising a most significant bit (MSB) which is followed by (m-1) bits;

converting each of said starting signals to a corresponding converted signal represented by "n" bits comprising an MSB followed by (n-1) bits the last of which is an LSB where (m-n)>

(+1), and the LSB of each converted signal is determined in part on the basis of a probability related to at least some of the bits following the n-th bit of the corresponding starting signal; and

utilizing said converted signals for at least temporarily one of displaying, televising, printing or transmitting.