Classifications

• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/2003—Display of colours
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
  • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
  • G09G3/3611—Control of matrices with row and column drivers
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2300/00—Aspects of the constitution of display devices
  • G09G2300/04—Structural and physical details of display devices
  • G09G2300/0439—Pixel structures
  • G09G2300/0443—Pixel structures with several sub-pixels for the same colour in a pixel, not specifically used to display gradations
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2300/00—Aspects of the constitution of display devices
  • G09G2300/04—Structural and physical details of display devices
  • G09G2300/0439—Pixel structures
  • G09G2300/0452—Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2320/00—Control of display operating conditions
  • G09G2320/02—Improving the quality of display appearance
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2340/00—Aspects of display data processing
  • G09G2340/02—Handling of images in compressed format, e.g. JPEG, MPEG
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2340/00—Aspects of display data processing
  • G09G2340/04—Changes in size, position or resolution of an image
  • G09G2340/0407—Resolution change, inclusive of the use of different resolutions for different screen areas
  • G09G2340/0414—Vertical resolution change
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2340/00—Aspects of display data processing
  • G09G2340/04—Changes in size, position or resolution of an image
  • G09G2340/0407—Resolution change, inclusive of the use of different resolutions for different screen areas
  • G09G2340/0428—Gradation resolution change
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2340/00—Aspects of display data processing
  • G09G2340/04—Changes in size, position or resolution of an image
  • G09G2340/0457—Improvement of perceived resolution by subpixel rendering
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/2007—Display of intermediate tones
  • G09G3/2074—Display of intermediate tones using sub-pixels

Definitions

• the present invention relates to methods and apparatus for displaying images, and more particularly, to methods and apparatus for increasing the perceived resolution of the displayed images and compressing image data to enable control signals to be efficiently transmitted to display devices.
• the Prior State of the Art Color display devices have become the principal display devices of choice for most computer users.
• the display of color on a monitor is normally achieved by operating the display device to emit light, typically a combination of red, green, and blue light, which results in one or more colors being perceived by a human viewer.
• CTR cathode ray tube
• the different colors of light are generated by phosphor coatings that may be applied as dots in a sequence on the screen of the CRT.
• a different phosphor coating is normally used to generate each of the red, green, and blue colors, resulting in repeating patterns of phosphor dots.
• the phosphor dots When excited by a beam of electrons, the phosphor dots generate the colors red, green and blue.
• the term pixel is commonly used to refer to one spot in, for example, a rectangular grid of thousands of such spots. Many computer applications and other types of applications assume that each pixel corresponds to a square portion of a display screen. Pixels are individually used by a computer to form an image on the display device.
• a color CRT where a single triad of red, green and blue phosphor dots cannot be addressed, the smallest possible pixel size will depend on the focus, alignment and bandwidth of the electron guns used to excite the phosphors.
• the light emitted from one or more triads of red, green and blue phosphor dots in various arrangements known for CRT displays, tends to blend together giving, at a distance, the appearance of a single colored light source representing a pixel.
• LCDs liquid crystal displays
• other flat panel display devices are commonly used in portable computer devices in place of CRTs. This is because flat panel displays tend to be small and lightweight in comparison to CRT displays.
• flat panel displays generally consume less power than comparably sized CRT displays, making them better suited for battery powered applications.
• CRT displays As the quality of flat panel color display devices increases and their cost decreases, flat panel displays continue to replace CRT displays in desktop applications. Accordingly, flat panel displays, and LCDs in particular, are becoming ever more common.
• Color LCD displays are exemplary of display devices that utilize multiple separately addressable and controllable elements, referred to herein as "pixel subcomponents," to represent each pixel of an image being displayed.
• pixel subcomponents each pixel is a single square element that includes non-square red, green and blue (RGB) pixel sub-components. When combined, the RGB pixel subcomponents form the square pixel.
• Fig. 1 illustrates a portion of a known LCD device 100.
• the illustrated LCD device 100 includes four columns (C1-C4) and three rows (R1-R3) of pixels, each of which has a separate red pixel sub-component 102, green pixel sub-component 104 and blue pixel sub-component 106.
• Each of the three pixel sub-components 102, 104, 106 is three times taller than it is wide.
• the RGB pixel sub-components 102, 104, 106 produce a square pixel.
• the RGB pixel sub-components 102, 104, 106 are arranged to form stripes along LCD device. The RGB stripes normally run the entire length of the display in one direction.
• the most complex Kanji character has nine horizontal lines, thus requiring 17 pixels to represent the lines and the spaces between them.
• display resolutions near 100 dots per inch, a true representation is not feasible at font sizes smaller than about 14 point type (14/72 of an inch).
• display devices simply do not have enough dots to depict complex Kanji characters at text sizes that would be preferred for comfortable reading.
• Japanese books are commonly printed in 9, 10 and 11 -point type, which are similar to those used in Western books. This is a desirable size for reading based on human physiology.
• Manga comic books hugely popular in Japan, use even smaller type sizes.
• small frutigana characters used to provide Japanese with pronunciation guidance for less-common Kanji characters are typically displayed using 3 or 4 point type.
• Representing characters at these sizes on computer screens, particularly LCDs presents huge challenges.
• One known technique to addressing the unavailability of screen pixels to represent the full strokes of complex characters has been to use hand-tuned bitmaps at small sizes. Unfortunately, these hand-tuned bitmaps are, at best, crude representations of characters that cannot be drawn accurately at the desired display sizes given the resolution of conventional displays.
• the present invention relates to methods and systems for improving the resolution of displayed images in the horizontal and vertical dimensions of LCD or other flat panel display devices that have separately controllable pixel subcomponents.
• One factor that is responsible for at least some of the improved resolution is that the separately controllable pixel sub-components, rather than full pixels, are treated as individual luminous intensity sources.
• Each pixel subcomponent represents a spatially different portion of the image.
• spatially different sets of one or more samples of the image data are mapped to the individual pixel sub-components, rather than to entire pixels.
• Such displaced sampling is responsible for increasing the resolution of the display device in the direction perpendicular to the stripes of the display device.
• Increased resolution in the orthogonal direction is achieved by increasing the pixel sub-component density beyond that of conventional display devices.
• each region of the display device that would ordinarily consist of a single pixel with three pixel sub-components is configured to include two or three full pixels, each having three pixel subcomponents.
• the pixel sub-components have heights 1.5 times greater than their widths if the pixel sub-component density is doubled, or are square if the density is tripled.
• the pixel sub-component density can be increased by other factors, as well, although a factor of two or three has the advantage that the height dimension is no smaller than the width dimension, and existing pixel sub-component manufacturing techniques can be readily adapted to construct such display devices.
• Display devices having the foregoing pixel and pixel sub-component configurations can enable images to be displayed with resolutions that are improved both in the vertical and horizontal dimensions compared with conventional rendering processes.
• the two-dimensional improvement in resolution can be particularly advantageous for displaying complex characters, such as Kanji characters, that rely heavily character features that have fine detail in both the horizontal and vertical dimensions.
• the image data compression processes are adapted to encode the luminous intensity values to be applied to a set of vertically adjacent pixels referred to as a control element of the display device.
• the control element includes a set of two vertically adjacent pixels when the pixel sub-component density is doubled and a set of three vertically adjacent pixels when the pixel sub-component density is tripled, such that the control element occupies a substantially square portion of the display device.
• the luminous intensity values applied to the pixel sub-components in a control element are encoded in a data structure having a length, for example, of 8, 16, or 24 bits.
• the data structure includes a red luminous intensity value, a green luminous intensity value, a blue luminous intensity value, and a bias value.
• the red, green, and blue luminous intensity values correspond to the overall or average luminance to be generated in the pixel sub-components of the control element.
• the bias value indicates the relative luminance between the multiple pixels in the control element. For instance, if the control element includes two vertically adjacent pixels, the bias value indicates whether the luminance is to be biased toward the upper pixel, toward the lower pixel, or to be distributed evenly.
• the data compression techniques of the invention allow the control signal to be transmitted to the display device at substantially the same rate as would be experienced if the pixel sub-component density were not increased.
• the compressed control signal for the display device having the increased pixel sub-component density can also use 16 bits of data per control element (i.e., square region of the display device).
• the cost of the data compression is generally the loss of some resolution compared to the resolution that would be obtained if each pixel were to be independently controlled without data compression.
• the invention also extends to display devices that are further adapted to decrease the color artifacts that can be generated from treating each pixel sub- component as a separate luminance source.
• the position of the red and blue pixel sub-components in a pixel is transposed in alternating adjacent rows. This pixel sub-component configuration breaks up the vertical stripes of same colored red and blue pixel sub-components that are present in many conventional display devices, thereby diminishing the color fringing effects that can be experienced.
• successive rows of pixels have red, green, and blue pixel sub-components that are offset by 1/3 or 2/3 the width of the full pixel, so that the stripes are not formed from same-colored pixel sub-components, but are instead formed from alternating red, green, and blue pixel sub-components.
• Figure 1 illustrates a portion of a conventional liquid crystal display device.
• Figure 2 illustrates an exemplary system that provides a suitable operating environment for embodiments of the present invention.
• Figure 3 illustrates a display device in which the position of the red and blue pixel sub-components is transposed on alternating rows of the display device according to one embodiment of the present invention.
• Figures 4A and 4B depict portions of a display device having a pixel subcomponent density in the vertical dimension that has been increased by a factor of two according to one embodiment of the invention.
• Figures 4C and 4D depict portions of a display device having a pixel subcomponent density in the vertical dimension that has been increased by a factor of two and that also has the position of the red and blue pixel sub-components transposed on alternating rows according to one embodiment of the invention.
• Figures 5A and 5B illustrate portions of a display device in which the pixel sub-component density in the vertical dimension has been increased by a factor of three.
• Figures 6 and 7 qualitatively illustrate improvements in readability of various
• Kanji characters that can be obtained by increasing the pixel sub-component density in the vertical dimension.
• the present invention relates to systems and methods for increasing the resolution of images displayed on LCD or other display devices having pixels that include separately controllable pixel sub-components. Assuming that the display device have vertical stripes, much of the enhanced resolution in the horizontal dimension is achieved by performing displaced sampling on the image data and mapping the displaced samples to individual pixel sub-components instead of mapping samples to full pixels. The improved resolution in the vertical dimension is achieved by increasing the pixel sub-component density in the vertical dimension. To accommodate the increased number of pixel sub-components, the invention also relates to image data compression techniques whereby sets of vertically adjacent pixels are controlled using a red luminous intensity value, a green luminous intensity value, a blue luminous intensity value, and a bias value.
• the red, green, and blue luminous intensity values control the overall luminance from the sets of red, green, and blue pixel sub-components, while the bias value indicates if, and to what extent, the luminance is to be shifted to a particular pixel in the set of pixels.
• Embodiments of the present invention may comprise a special purpose or general purpose computer including various computer hardware, as discussed in greater detail below.
• Embodiments within the scope of the present invention also include computer-readable media for carrying or having computer-executable instructions or data structures stored thereon.
• Such computer-readable media can be any available media which can be accessed by a general purpose or special purpose computer.
• Such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code means in the form of computer-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer.
• Computer-executable instructions comprise, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions.
• FIG. 2 and the following discussion are intended to provide a brief, general description of a suitable computing environment in which the invention may be implemented.
• the invention will be described in the general context of computer-executable instructions, such as program modules, being executed by computers in network environments.
• program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types.
• Computer-executable instructions, associated data structures, and program modules represent examples of the program code means for executing steps of the methods disclosed herein.
• the particular sequence of such executable instructions or associated data structures represent examples of corresponding acts for implementing the functions described in such steps.
• the invention may be practiced in network computing environments with many types of computer system configurations, including personal computers, hand-held devices, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, and the like.
• the invention may also be practiced in distributed computing environments where tasks are performed by local and remote processing devices that are linked (either by hardwired links, wireless links, or by a combination of hardwired or wireless links) through a communications network.
• program modules may be located in both local and remote memory storage devices.
• an exemplary system for implementing the invention includes a general purpose computing device in the form of a conventional computer 20, including a processing unit 21, a system memory 22, and a system bus 23 that couples various system components including the system memory 22 to the processing unit 21.
• the system bus 23 may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures.
• the system memory includes read only memory (ROM) 24 and random access memory (RAM) 25.
• ROM read only memory
• RAM random access memory
• a basic input/output system (BIOS) 26, containing the basic routines that help transfer information between elements within the computer 20, such as during start-up, may be stored in ROM 24.
• the computer 20 may also include a magnetic hard disk drive 27 for reading from and writing to a magnetic hard disk 39, a magnetic disk drive 28 for reading from or writing to a removable magnetic disk 29, and an optical disk drive 30 for reading from or writing to removable optical disk 31 such as a CD-ROM, CD-R, CD- RW or other optical media.
• the magnetic hard disk drive 27, magnetic disk drive 28, and optical disk drive 30 are connected to the system bus 23 by a hard disk drive interface 32, a magnetic disk drive-interface 33, and an optical drive interface 34, respectively.
• the drives and their associated computer-readable media provide nonvolatile storage of computer-executable instructions, data structures, program modules and other data for the computer 20.
• exemplary environment described herein employs a magnetic hard disk 39, a removable magnetic disk 29 and a removable optical disk 31
• other types of computer readable media for storing data can be used, including magnetic cassettes, flash memory cards, digital video disks, Bernoulli cartridges, RAMs, ROMs, and the like.
• Program code means comprising one or more program modules may be stored on the hard disk 39, magnetic disk 29, optical disk 31, ROM 24 or RAM 25, including an operating system 35, one or more application programs 36, other program modules 37, and program data 38.
• a user may enter commands and information into the computer 20 through keyboard 40, pointing device 42, or other input devices (not shown), such as a microphone, joy stick, game pad, satellite dish, scanner, or the like.
• These and other input devices are often connected to the processing unit 21 through a serial port interface 46 coupled to system bus 23.
• the input devices may be connected by other interfaces, such as a parallel port, a game port or a universal serial bus (USB).
• a monitor 47 or another display device is also connected to system bus 23 via an interface, such as video adapter 48.
• the computer 20 may operate in a networked environment using logical connections to one or more remote computers, such as remote computers 49a and 49b.
• Remote computers 49a and 49b may each be another personal computer, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computer 20, although only memory storage devices 50a and 50b and their associated application programs 36a and 36b have been illustrated in Figure 2.
• the logical connections depicted in Figure 2 include a local area network (LAN) 51 and a wide area network (WAN) 52 that are presented here by way of example and not limitation.
• LAN local area network
• WAN wide area network
• the computer 20 When used in a LAN networking environment, the computer 20 is connected to the local network 51 through a network interface or adapter 53. When used in a WAN networking environment, the computer 20 may include a modem 54, a wireless link, or other means for establishing communications over the wide area network 52, such as the Internet.
• the modem 54 which may be internal or external, is connected to the system bus 23 via the serial port interface 46.
• program modules depicted relative to the computer 20, or portions thereof may be stored in the remote memory storage device. It will be appreciated that the network connections shown are exemplary and other means of establishing communications over wide area network 52 may be used.
• the first and second dimensions of a display device are commonly referred as vertical (y) and horizontal (x) dimensions, respectively.
• the horizontal and vertical dimensions can be interchanged.
• the methods and apparatus of the present invention will be explained in terms of vertical and horizontal dimensions.
• the described exemplary display devices can be rotated to achieve the described improvement in resolution in the vertical direction in the horizontal direction, and the described improvement in resolution in the horizontal direction, in the vertical direction.
• pixel elements commonly include red, green and blue pixel sub-components.
• each pixel sub-component may be separately controlled by selecting a luminous intensity control value associated with the particular pixel sub-component.
• each R, G and B pixel sub-component is rectangular in shape and is three times taller than it is wide.
• the three rectangular pixel sub-components form a square pixel.
• R, G, B luminous intensity values are independently controlled to represent different portions of an image. This provides an increase in the horizontal spatial resolution of up to three times over those of conventional rendering techniques that use the entire pixel to represent a single portion of an image.
• treating the pixel sub-components as separate luminous intensity sources can result in some color distortions. For example, undesired red and/or green vertical stripes or fringes may be visible in a displayed image.
• the common RGB striped display pattern is replaced with a pattern that transposes the position of red and blue pixel sub-components in alternating rows, as illustrated in Fig. 3.
• Row Rl of display device 200 includes a series of pixel sub-components having an (R, G, B, R, G, B, . . .) pattern.
• row R2 includes a series of pixel sub-components having an (B, G, R, B, G, R, . . .) pattern.
• the vertically adjacent pixel sub-components 202 and 212 have different colors (red and blue)
• the vertically adjacent pixel sub-components 206 and 214 have the same green color
• the vertically adjacent pixel subcomponents 208 and 216 have different colors (blue and red).
• Such pixel sub-component configurations can reduce the effect of color artifacts by eliminating the contiguous red and blue vertical pixel sub-component stripes. It is these contiguous vertical color strips that can produce distracting red and blue fringing effects in an image. Rather than having vertical stripes of same-colored red and blue pixel sub-components, LCD device 200 has vertical stripes of alternating red and blue pixel sub-components.
• the foregoing techniques of treating pixel sub-components as independent luminous sources can result in a significant increase in spatial resolution in the dimension perpendicular to the direction of the stripes.
• this method of increasing image resolution is particularly useful for rendering Latin-based characters or other characters that rely more heavily on vertical character features than horizontal character features.
• Kanji characters generally depend as heavily on horizontal character features as they do on vertical features. Accordingly, to increase the legibility of Kanji characters, it is important to increase vertical as well as horizontal resolution.
• resolution is increased in the vertical dimension by increasing the number of pixel sub-components in this dimension.
• the number of pixel sub-components per unit distance in the direction parallel to the stripes can be doubled with respect to the conventional display device illustrated in Figure 1.
• FIGs 4A and 4B One example of such a display device is illustrated in Figures 4A and 4B.
• the portion of LCD display device 320 illustrated in Figure 4B includes rows R1-R3 and columns C1-C4. Rows R1-R3 represent scanlines of the display device 320 that are oriented perpendicularly to the vertical striping. In contrast, display devices having horizontal striping have vertical scanlines.
• Each region of LCD device 320 that would correspond to a single full pixel with three pixel sub-components in a conventional display device instead represents two pixels containing a total of six pixel sub-components.
• Figure 4A illustrates one such region 300 of display device 320, which includes separately controllable pixel sub-components Rl, Gl, Bl, R2, G2, and B2, indicated by reference numbers 302, 304, 306, 312, 314, and 316, respectively.
• the pixel and pixel sub-component configuration of Figures 4A and 4B results in pixel sub-components that are approximately 1.5 times taller than they are wide. In other words, the aspect ratio of the pixel sub-components is approximately 1.5:1. It is noted that the aspect ratios can describe the size and relative positioning of the pixel sub-components regardless of whether the display device has vertical or horizontal stripes.
• the decreased aspect ratio of the pixel sub-components of Figures 4 A and 4B has the effect of increasing the resolution in the vertical direction. The apparent factor by which the resolution is increased depends largely on the manner in which the pixel sub-components 302, 304, 306, 312, 314, and 316 are controlled, as will be described in greater detail below.
• Figures 4C and 4D depict a portion of an LCD device 350 that has pixel subcomponents that are approximately 1.5 times taller than they are wide, as in the example of Figures 4A and 4B, in combination with transposing the position of the red and green pixel sub-components on alternating rows as has been described in reference to Figure 3.
• region 330 of Figure 4C includes pixel sub-components Rl, Gl, Bl, B2, G2, R2 indicated by reference numbers 332, 334, 336, 342, 344, and 346, respectively.
• each region of display device 450 that would correspond to a single full pixel in conventional LCD devices instead represents three pixels that include a total of nine pixel subcomponents.
• region 400 of Figure 5A includes pixel sub-components Rl, Gl, Bl, R2, G2, B2, R3, G3, B3 indicated by reference numbers 402, 404, 406, 408, 410, 412, 414, 416, and 418, respectively.
• the pixel and pixel sub-component configuration of Figures 5 A and 5B results in pixel sub-components that are square or approximately square, or have aspect ratios of approximately 1 :1.
• the doubling or tripling of the resolution in the vertical dimension can be implemented using existing display device manufacturing equipment since it does not require a finer gradation between pixel sub-components than is already found in the horizontal dimension.
• Such treatment in the case where the pixel sub-component density is increased by a factor of two, results in non-square pixels that are half as tall as they are wide.
• the display software In order to fully use all of the pixels, the display software generates and transmits a signal containing twice as many luminous intensity values associated with pixel sub-components than would be needed if the pixel sub-component density had not been increased by a factor of two.
• the pixel sub-component density is increased by a factor of three, the number of luminous intensity values is also tripled if the pixel sub-components are to be fully and independently utilized to represent different portions of the image data.
• the large number of luminous intensity values that are to be transmitted in the control signal for display devices can present bandwidth problems in some systems. That is, some systems may not be capable of generating and transmitting such a large number of independent luminous intensity values during the time available for each update of the display device.
• many existing image processing applications assume that pixels are square. There may be some inefficiencies or complexities associated with using non-square pixels with such applications.
• embodiments of the present invention relate to compressing the luminous intensity values associated with the pixel sub-components of display devices having increased pixel sub-component densities. The data compression sacrifices some resolution in exchange for reducing the data transmission requirements to render images.
• each set, or triad, of RGB pixel sub-components can be treated as an independent pixel without using the data compression techniques disclosed herein.
• sets of pixels are grouped together for control purposes.
• FIGs 4A-4D where the pixel sub-component density is doubled in the vertical dimension, two sets of vertically adjacent RGB pixel subcomponents can be grouped together to form a pair of adjacent pixels that is referred to herein as a "control element".
• region 300 of Figure 4 A and region 400 of Figure 5A are examples of control elements.
• each pair of pixels occupies a generally square region of the display device and corresponds in size to a single pixel of a conventional display device.
• the control element can consist of adjacent pixels, control elements can, in general, consist of two or more pixels, regardless of whether the pixels are adjacent one to another.
• the luminance generated by the pixel sub-components in each control element is controlled using a single red luminous intensity value, a single green luminous intensity value, a single blue luminous intensity value, and a bias value.
• the bias value indicates how the light energy specified by the R, G and B luminous intensity values should be distributed or differentially applied between the upper pixel and the lower pixel of the control element.
• the bias value indicates, for example, whether the luminance should be evenly distributed between the upper and lower pixels, or whether it should be weighted by a specified factor to the upper or lower pixel.
• Opportunity for bias depends on the specified luminous intensity of each color component. Accordingly, in the case where the different color components are assigned different luminous intensity values, the opportunity for bias will be different for each of the R, G and B components. Medium gray offers a large opportunity for bias, since the R, G and B luminous intensity values are each at their midrange point.
• the number of bits included in the red, green, and blue luminous intensity values and the bias value can be selected in view of empirical observations relating to the perception of colors by humans. In general, most humans can perceive green light far better than red or blue light. Studies have shown that, in general, of the total perceived luminous intensity of a light source that outputs red, green, and blue light of the same luminous intensity, approximately 60% of the perceived luminous intensity is associated with the green light, 30% with the red light, and 10% with the blue light. For this reason, humans tend to be able to distinguish differences in green luminous intensity values far better than differences in red or blue luminous intensity values.
• the luminous intensity of the R, G, and B pixel sub-components is controlled using a control signal that includes 8, 16 or 24 bits per pixel. Multiples of eight bits are frequently used in control signals to efficiently use the data capacity of data words used to transmit such signals.
• Conventional systems that use a total of eight bits to specify the luminous intensity values of red, green and blue pixel sub-components of a single pixel normally allocate three bits for specifying the red luminous intensity value, three bits for specifying the green luminous intensity value and two bits for specifying the blue luminous intensity value.
• a display device having an increased pixel subcomponent density can be controlled using control signals that require no more data to transmit.
• the cost of performing such data compression is often the loss of some spatial or color resolution in the rendered image.
• a display device having two pixels in each control element can be controlled using an 8-bit signal where two bits are used for the R luminous intensity value, two bits for the G luminous intensity value, two bits for the B luminous intensity value, and two bits for the bias value.
• two bits are used for the R luminous intensity value, two bits for the G luminous intensity value, two bits for the B luminous intensity value, and two bits for the bias value.
• 16 bits are available per control element
• four bits can be used to specify the red luminous intensity value, six to specify the green luminous intensity value, four to specify the blue luminous intensity value, and two bits to specify the bias value.
• eight bits can be used to specify the red luminous intensity value, eight to specify the green luminous intensity value, six to specify the blue luminous intensity value, and two bits to specify the bias value.
• each pair of bias bits represents a separate red, green and blue bias signal.
• a two-bit bias value can indicate whether or not a bias is to be applied, and whether the upper or lower RGB set should be responsible for outputting the majority of the light energy from the pixel element.
• a bias control signal value 00 indicates that the luminous energy should be spread evenly between the upper and lower pixels
• a bias control signal value 10 indicates that the luminous energy should be biased downward so that the lower pixel outputs more light than the upper pixel
• a bias control signal value of 01 indicates that the luminous energy should be biased upward so that the upper pixel outputs more light than the lower pixel.
• the luminous intensity control techniques of the present invention which involve the use of separate R, G, B luminous intensity values, in conjunction with a bias value, can be used to control pixel elements comprising three or more sets of R, G and B luminous intensity values.
• Such a control method is particularly well suited to applications where the pixel sub-component density have been tripled in the vertical dimension so that individual RGB pixel sub-components are square and have vertical and horizontal dimensions equal to 1/3 the width of a pixel.
• three vertically adjacent pixels can be grouped together to form a singe square control element.
• each control element includes three sets of RGB pixel sub-components
• a 3 -bit bias control signal is used.
• the 3 -bit bias signal supports a large enough number of different luminous intensity energy distributions that reasonable use of the available vertical resolution, corresponding to the three vertically adjacent pixels, can be obtained.
• the values of the bias bits can be derived by sampling image data such that the vertical distance between vertically adjacent samples is equal to the height of the pixel sub-components.
• To select the bias bits first the two (or three) desired RGB luminous intensity values are averaged together, component-wise, and each color is quantized to the appropriate level for the display device. This average of the RGB luminous intensity values corresponds to the desired overall luminance for the control element. Next, the overall luminance that would be generated in the control element for each possible bias bit setting is computed and compared to the averaged desired output for the control element.
• These control element outputs are patterns consisting of two by three emitters or three by three emitters, as disclosed herein.
• the bias bits are chosen to minimize the square of the Euclidean distance between the averaged desired control element output and the actual control element output.
• Other error metrics can also be used, including those that will be obvious to those skilled in the art upon learning of the invention disclosed herein.
• the results of the resolution-enhancing filtering can be quantized as one 8-bit value per control element.
• the vertical pixel sub-component density (and the corresponding rate of sampling) is increased by a factor of two.
• two 8-bit filtered RGB values are to be converted into one 8 -bit signal including the RGB luminous intensity values and the bias value.
• This conversion can be accomplished via a lookup table, using techniques that will be understood by those skilled in the art, upon learning of the invention disclosed herein. If the lookup table is accomplished in software by the operating system, it does not require a large amount of computation. Alternatively, the lookup table can be implemented in hardware in a video card. IV. Examples of Characters
• Figures 6 and 7 qualitatively illustrate the increased resolution that can often be obtained by displaying images according to the invention.
• the characters of Figures 6 and 7 are those that can be generated by independently controlling each pixel rather than using the data compression techniques of the invention, with the bias values.
• the characters illustrated in Figures 6 and 7 are presented by way of example, and not by limitation. The results of any particular rendering process will depend on many factors, including the size of the pixel sub-components, the sampling and filtering processes used, etc.
• Figure 6 illustrates various representations of the Japanese character "Utsu,” which is reputed as being one of the most complex Kanji characters.
• the characters of Figure 7 illustrate how an outline-only rendered bitmap may be rendered at different font sizes and at different pixel sub-component densities, both in the vertical and horizontal dimensions.
• Set of characters 130 is displayed with 9-point type and corresponds to an LCD display device having 88 dpi (i.e., 88 full pixels per inch).
• Character 130a is rendered using a display device with pixel sub-components that are three times as tall as they are wide or, in other words, with no increased pixel sub-component density.
• Character 130b is displayed using the same display device, but with an increase in the pixel sub-component density by a factor of two.
• Character 130c is displayed with an increase in the pixel sub-component density by a factor of three compared to that of character 130a.
• Set of characters 132 is displayed with 9-point type and corresponds to an LCD display device having 106 dpi.
• Character 132a is rendered using a display device with pixel sub-components that are three times as tall as they are wide.
• Character 132b is displayed using the same display device, but with an increase in the pixel sub-component density by a factor of two.
• Character 132c is displayed with an increase in the pixel sub-component density by a factor of three compared to that of character 132a.
• Set of characters 134 is displayed with 6-point type and corresponds to an LCD display device having 88 dpi.
• Character 134a is rendered using a display device with pixel sub-components that are three times as tall as they are wide.
• Character 134b is displayed using the same display device, but with an increase in the pixel sub- component density by a factor of two.
• Character 134c is displayed with an increase in the pixel sub-component density by a factor of three compared to that of character 134a.
• Set of characters 136 is displayed with 6-point type and corresponds to an LCD display device having 106 dpi.
• Character 136a is rendered using a display device with pixel sub-components that are three times as tall as they are wide.
• Character 136b is displayed using the same display device, but with an increase in the pixel sub-component density by a factor of two.
• Character 136c is displayed with an increase in the pixel sub-component density by a factor of three compared to that of character 136a.
• Figure 7 illustrates various Kanji characters as they can appear when displayed according to the invention.
• Row 140 includes characters that correspond to an LCD display device having 88 dpi and where the conventional pixel sub-component density has been increased by a factor of two.
• Row 142 includes characters that correspond to an LCD display device having 106 dpi and where the conventional pixel subcomponent density has been increased by a factor of two.
• Row 144 represents the characters of row 140 having been displayed with a pixel sub-component density increased by a factor of three, rather than two.
• row 146 represents the characters of row 142 having been displayed with a pixel sub-component density increased by a factor of three, rather than two.

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