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
  • G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
  • G09G5/20—Function-generator circuits, e.g. circle generators line or curve smoothing circuits
• • 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
  • G09G3/34—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
  • G09G3/3607—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 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels

Definitions

• the present invention relates to displaying images.
• the present invention relates to improving image-display quality by adaptive subpixel rendering.
• Multicolor displays typically use pixels that are constructed from discrete red, green and blue subpixels.
• liquid crystal displays LCDs
• LCDs liquid crystal displays
• three spatially-offset color components including red, green and blue subpixels.
• color components in an LCD screen is shown in
• Figure 1 which consists of rectangular areas formed by arranged the red, green and blue components in a horizontal line.
• pixel 101 in this example consists of red subpixel 101a, green subpixel 101b and blue subpixel 101c.
• red subpixel 101a red subpixel 101a
• green subpixel 101b red subpixel 101c
• blue subpixel 101c blue subpixel 101c
• Each of the color components can be individually controlled by an LCD controller to produce different shades of color. Because each set of the color components belongs to a single pixel, however, in many image processing algorithms, including image rendering or rasterization, the subpixels are treated as if they co- locate in a single coordinate with many similar attributes. This can lead to jagged lines and inferior image display quality.
• Figure 2 shows an example of a diagonal line displayed using a typical pixel-rendering scheme. As can be seen from this picture, the line is jagged. Ways exist to address this problem, including methods of anti- aliasing.
• a typical anti-aliased diagonal line is shown in Figure 3. Using antialiasing, pixels adjacent to the blackened pixel are displayed in various shades of gray, thereby allowing the eye to smooth the line.
• Embodiments of the present invention allow for improved display quality by employing methods and devices that perform adaptive subpixel rendering.
• a method for displaying an image comprises receiving pixel data representing an image, determining an image feature in the received pixel data, and generating a subpixel drive correction signal based on the determined image.
• the subpixel drive correction signal is based on an attribute of a display device.
• Figure 1 is a representation of a known subpixel structure.
• Figure 2 is a representation of an example of a diagonal line displayed using a typical pixel-rendering scheme.
• Figure 3 is a representation of an example of a diagonal line displayed using an anti-aliasing scheme.
• Figure 4 is a flow chart of an embodiment of the present invention.
• Figure 5 is a flow chart of calculations, according to an embodiment of the present invention.
• Figure 6 is a block diagram of an apparatus according to an embodiment of the present invention, including a processor, a memory and a port.
• Figure 7 is a block diagram of another apparatus embodiment of the present invention, including an I/O Buffer, and Address Counter, a RAM, a Timing Generator, a MPU Interface, a Command Decoder, a Subpixel Feature Enhancer, and an Apparatus Driver.
• Figure 8 is a representation of a black vertical line, illustrating an embodiment of the present invention.
• Figure 9 is a representation of a diagonal line, according to an embodiment of the present invention.
• Embodiments of the present invention provide improved image-display quality using adaptive subpixel rendering. If desired, embodiments of the present invention can use attributes of a display device to provide the improved image-display quality.
• FIG. 4 is a flow chart of an embodiment of the present invention.
• pixel data representing an image is received at step 401.
• an image feature in the received pixel data is determined.
• a subpixel drive correction signal is generated.
• a drive signal based on the subpixel drive correction signal is generated.
• the subpixel drive correction signal can be based on an attribute or attributes of a given display device.
• a display device can be an LCD.
• the attributes can include, but are not limited to, subpixel configurations such as the relative position of the subpixels, the size of the subpixels, the shape of the subpixels, the geometry of the subpixels and the orientation of the subpixels.
• the red, green and blue subpixels have a spatial offset from one another. These subpixel spatial offsets can be used to increase the spatial resolution of the image by a factor of N, where N is the number of color components for a given pixel.
• the finite size and shape of the subpixels are also attributes that can be used to enhance the image because they determine the size and shape of the image details that can best be represented by the subpixels.
• the geometry and the orientation are both concerned with the arrangement of the subpixels. Different arrangements allow our eyes to perceive sharper details at certain angles and frequencies, when the image is rendered at a subpixel level.
• the attribute of "intensity mapping" is used to enhance the image. Because the color components can be controlled individually by a pixel drive signal, by treating them as separate subpixels it is possible to use dynamic intensity mapping to further improve image quality.
• the pixel data received at step 401 can include subpixel data, and can be rendered or rasterized data.
• rasterization means determining pixel values from input geometric primitives.
• the image feature detection performed at step 402 can be performed in any known way.
• to make use of the subpixel attributes after the information of the rendered image is passed on to, for example, but not the only example, a display controller, it is passed through a few stages of calculation.
• Figure 5 is a flow chart of such calculations, according to an embodiment of the present invention.
• N and M can include, for example (but not the only example) from 3 to 9 pixels.
• N and M can include, for example (but not the only example) from 3 to 9 pixels.
• N and M can include, for example (but not the only example) from 3 to 9 pixels.
• an edge in the input image block is detected, and at step 503, an edge metric is calculated.
• the edge metric can include, but is not limited to, information about the edge location, the edge orientation, and contrast.
• the detection and calculation can be performed by any appropriate operation. For example, but not the only example, edge detection and calculation can be performed by using the Sobel or Laplacian filter for edge detection. Other examples are described in Gonzalez and Woods, Digital Image Processing (Addison-Wesley, 1992), the relevant portions of which are hereby incorporated. The calculations can be performed on, for example, but not the only example, a single instruction, multiple data (SIMD) array processor.
• SIMD single instruction, multiple data
• pixel and subpixel attributes are combined with the edge metric.
• the image features can be rendered or rasterized appropriately with subpixel accuracy for any particular color attribute or component geometry in a display device. This rendering or rasterization can be performed in software using any appropriate algorithm.
• FIG. 6 is a block diagram of an apparatus according to an embodiment of the present invention.
• processor 601 is coupled to memory 602 and port 603, and memory 602 stores instructions adapted to be executed by processor to perform a method embodiment of the present invention.
• memory 602 stores instructions adapted to be executed by processor 601 to receive a rasterized image, detect a feature in the rasterized image, and then enhance the detected feature on a subpixel level.
• memory includes any computer-readable medium capable of storing instructions adapted to be executed by a processor.
• the instructions are stored on the medium in a compressed and/or encrypted format.
• the phrase "adapted to be executed by a processor" is meant to encompass instructions stored in a compressed and or encrypted format, as well as instructions that have to be compiled or installed by an installer before being executed by the processor.
• FIG. 7 is a block diagram of another apparatus embodiment of the present invention.
• I/O Buffer 701 is coupled to Address Counter 702.
• Address Counter 702 is coupled to RAM 703, which in turn is coupled to Timing Generator 704, Command Decoder 705, and Subpixel Feature Enhancer 706. Subpixel Feature Enhancer 706 and Timing Generator 704 are both coupled to Apparatus Driver 707, and Command Decoder 705 is coupled to MPU Interface 708.
• I/O Buffer 701 can receive rendered or rasterized data representing an image. Address Counter 702 can direct which of the data in I/O Buffer 701 is to be transferred to RAM 703 in the controller.
• Timing Generator 704 can provide a timing pattern for the entire controller, or some portion thereof.
• MPU Interface 708 can direct external commands to Command Decoder 705. wherein the commands can be subsequently directed to data stored in RAM 703.
• Subpixel Feature Enhancer 706 data representing an image block can be fed from RAM 703. Subpixel Feature Enhancer 706 can then determine particular image features in the received pixel data, such as the existence of an edge. If a particular feature is identified, the characteristics of the feature are also computed in
• Subpixel Feature Enhancer 706 such as the orientation and contrast of the edge. Taking into account the attributes of the display controller, Subpixel Feature Enhancer 706 can generate a subpixel drive correction signal to enhance the detected features. The resulting enhanced image data are fed to the display driver which interacts with the actual image display.
• FIG 8 which displays the simple case of a black vertical line, with a width of exactly one pixel wide.
• the vertical line is displaced by one-third with respect to the pixel grid.
• the intensity of the left column is reduced to two- third while the intensity of the second column is reduced to one-third, to give the impression to the eye that together they form a black vertical line, as shown in 8(b).
• the individual subpixel intensities are adjusted as in 8(c), where the red, green, and blue subpixels corresponding to the pixels in the left column are all reduced by two-thirds, and those corresponding to the pixels in the right column are all reduced by one-third.
• the red, green, and blue subpixels that correspond to the white pixels in the background are not shown.
• the image sharpness can be significantly enhanced with subpixel level rendering, taking into account the subpixel attributes.
• subpixel anti-aliasing scheme At neighborhood locations of the fine line that requires diminished intensity, one can selectively reduce the intensities of the red, green, or blue components to minimize the jaggedness and color distortions of the rendered line. This results in a smoother and clearer line than would be available from the conventional method.
• subpixel-level feature enhancement schemes for image display are not limited to anti-aliasing applications.
• another particular advantageous application is for low-end displays, such as palm-top organizers and mobile phones, in which maximum resolution texts should be displayed with as small a number of pixels as possible. For such devices, screen resolution is usually very limited.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Computer Hardware Design (AREA)
• General Physics & Mathematics (AREA)
• Theoretical Computer Science (AREA)
• Control Of Indicators Other Than Cathode Ray Tubes (AREA)
• Liquid Crystal Display Device Control (AREA)

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• 2000
  • 2000-10-19 AU AU10976/01A patent/AU1097601A/en not_active Abandoned
  • 2000-10-19 EP EP00972295A patent/EP1171868A1/de not_active Withdrawn
  • 2000-10-19 WO PCT/US2000/029037 patent/WO2001029817A1/en not_active Application Discontinuation
  • 2000-10-19 JP JP2001532529A patent/JP2003512653A/ja not_active Withdrawn

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