Method and Apparatus for Displaying Monochrome Images on a Color Monitor

Abstract

Disclosed is a method for increasing the number of grey levels used to create a monochrome image on a color display which comprises pixels with individual red, green, and blue color components. If the luminance value of each color component is controlled by an n-bit value, the number of true monochrome grey levels resulting from equal control values of each color is 2n. By adjusting the luminance of each color component such that the luminances of at least two color components are different from each other, intermediate values of luminance may be formed. Under specified conditions, the resulting light emission has intermediate luminance values which are perceived by human vision, and color values which are still perceived as grey. The resulting number of perceived grey levels is greater than 2n.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary imaging system in which the principles of the present invention may be implemented;

FIG. 2 is a flowchart of steps to transform a digital image value to a set of control values;

FIG. 3 shows a method for generating six intermediate perceived monochrome luminance values between two sequential true monochrome luminance values;

FIG. 4 shows a method for transforming a digital image value to a perceived monochrome luminance level via a look-up table;

FIG. 5 shows an algorithm for transforming a digital image value to a perceived monochrome luminance level;

FIG. 6 shows a method for transforming the least significant bits of a digital image value to an intermediate perceived monochrome level; and

FIG. 7 shows an embodiment of a signal processing system comprising a personal computer.

Claims

1. A method for increasing the perceived monochrome luminance values of a color display system capable of displaying a plurality of pixels, each pixel comprising a red color component, a blue color component, and a green color component, wherein the luminance of each color component is independently controllable according to an n-bit control value, and wherein each pixel is capable of displaying a plurality of true monochrome luminance values by setting the luminance of each color component of a pixel to a same n-bit control value thereby allowing the display of 2n true monochrome luminance values, the method comprising the steps of: receiving input digital image values comprising greater than 2n true monochrome luminance values; andgenerating intermediate perceived monochrome luminance values between first and second true monochrome luminance values by varying the n-bit control values of the color components of a pixel such that at least two of the n-bit control values of the color components of the pixel are different from each other.

2. The method of claim 1 wherein said step of generating intermediate perceived monochrome luminance values between two true monochrome luminance values by varying the n-bit control values of the color components of a pixel further comprises the steps of: generating a first intermediate perceived monochrome level by adding 1 bit to the control value of the blue color component of the first true monochrome luminance value;generating a second intermediate perceived monochrome level by adding 1 bit to the control value of the red color component of the first true monochrome luminance value;generating a third intermediate perceived monochrome level by adding 1 bit to each of the control values of the blue color component and the red color component of the first true monochrome luminance value;generating a fourth intermediate perceived monochrome level by adding 1 bit to the control value of the green color component of the first true monochrome luminance value;generating a fifth intermediate perceived monochrome level by adding 1 bit to each of the control values of the blue color component and the green color component of the first true monochrome luminance value; andgenerating a sixth intermediate perceived monochrome level by adding 1 bit to each of the control values of the red color component and the green color component of the first true monochrome luminance value.

3. The method of claim 1 wherein said input digital image values comprise 2n+x true monochrome luminance levels, said method further comprising the step of: mapping said input digital image value to an n-bit true monochrome luminance level and an intermediate perceived monochrome luminance level using a look-up table.

4. The method of claim 1 wherein said input digital image values comprise 2n+x true monochrome luminance levels, said method further comprising the step of: setting an n-bit true monochrome luminance level equal to n most significant bits of said digital image value; andcalculating an intermediate perceived monochrome luminance level from x least significant bits of said digital image value.

5. A system for increasing the perceived monochrome luminance values of a color display system capable of displaying a plurality of pixels, each pixel comprising a red color component, a blue color component, and a green color component, wherein the luminance of each color component is independently controllable according to an n-bit control value, and wherein each pixel is capable of displaying a plurality of true monochrome luminance values by setting the luminance of each color component of a pixel to a same n-bit control value thereby allowing the display of 2n true monochrome luminance values, the system comprising: means for receiving input digital image values comprising greater than 2n true monochrome luminance values; andmeans for generating intermediate perceived monochrome luminance values between first and second true monochrome luminance values by varying the n-bit control values of the color components of a pixel such that at least two of the n-bit control values of the color components of the pixel are different from each other.

6. The system of claim 5 wherein said means for generating intermediate perceived monochrome values between two true monochrome luminance values by varying the n-bit control values of the color components of a pixel further comprises: means for generating a first intermediate perceived monochrome level by adding 1 bit to the control value of the blue color component of the first true monochrome luminance value;means for generating a second intermediate perceived monochrome level by adding 1 bit to the control value of the red color component of the first true monochrome luminance value;means for generating a third intermediate perceived monochrome level by adding 1 bit to each of the control values of the blue color component and the red color component of the first true monochrome luminance value;means for generating a fourth intermediate perceived monochrome level by adding 1 bit to the control value of the green color component of the first true monochrome luminance value;means for generating a fifth intermediate perceived monochrome level by adding 1 bit to each of the control values of the blue color component and the green color component of the first true monochrome luminance value; andmeans for generating a sixth intermediate perceived monochrome level by adding 1 bit to each of the control values of the red color component and the green color component of the first true monochrome luminance value.

7. The system of claim 5 wherein said input digital image values comprise 2n+x true monochrome luminance levels, said system further comprising: means for mapping said input digital image value to an n-bit true monochrome luminance level and an intermediate perceived monochrome luminance level using a look-up table.

8. The system of claim 5 wherein said input digital image values comprise 2n+x true monochrome luminance levels, said system further comprising: means for setting an n-bit true monochrome luminance level equal to n most significant bits of said digital image value; andmeans for calculating an intermediate perceived monochrome luminance level from x least significant bits of said digital image value.

9. A computer readable medium storing computer program instructions for increasing the perceived monochrome luminance values of a color display system capable of displaying a plurality of pixels, each pixel comprising a red color component, a blue color component, and a green color component, wherein the luminance of each color component is independently controllable according to an n-bit control value, and wherein each pixel is capable of displaying a plurality of true monochrome luminance values by setting the luminance of each color component of a pixel to a same n-bit control value thereby allowing the display of 2n true monochrome luminance values, the computer program instructions defining the steps of: receiving input digital image values comprising greater than 2n true monochrome luminance values; andgenerating intermediate perceived monochrome luminance values between first and second true monochrome luminance values by varying the n-bit control values of the color components of a pixel such that at least two of the n-bit control values of the color components of the pixel are different from each other.

10. The computer readable medium of claim 9 wherein said computer program instructions defining the step of generating intermediate perceived monochrome values between two true monochrome luminance values by varying the n-bit control values of the color components of a pixel further comprise computer program instructions defining the steps of: generating a first intermediate perceived monochrome level by adding 1 bit to the control value of the blue color component of the first true monochrome luminance value;generating a second intermediate perceived monochrome level by adding 1 bit to the control value of the red color component of the first true monochrome luminance value;generating a third intermediate perceived monochrome level by adding 1 bit to each of the control values of the blue color component and the red color component of the first true monochrome luminance value;generating a fourth intermediate perceived monochrome level by adding 1 bit to the control value of the green color component of the first true monochrome luminance value;generating a fifth intermediate perceived monochrome level by adding 1 bit to each of the control values of the blue color component and the green color component of the first true monochrome luminance value; andgenerating a sixth intermediate perceived monochrome level by adding 1 bit to each of the control values of the red color component and the green color component of the first true monochrome luminance value.

11. The computer readable medium of claim 9 wherein said input digital image values comprise 2n+x true monochrome luminance levels, said computer program instructions further defining the step of: mapping said input digital image value to an n-bit true monochrome luminance level and an intermediate perceived monochrome luminance level using a look-up table.

12. The computer readable medium of claim 9 wherein said input digital image values comprise 2n+x true monochrome luminance levels, said computer program instructions further defining the step of: setting an n-bit true monochrome luminance level equal to n most significant bits of said digital image value; andcalculating an intermediate perceived monochrome luminance level from x least significant bits of said digital image value.