Wide dynamic range vector data raster display
A wide dynamic range vector data raster display of a waveform image is obtained by using a small matrix of pixels from a source frame buffer containing waveform image data to calculate a value for each pixel on a target display. Any of several algorithms may be used for this transform function, such as the unsharp masking (USM) algorithm used in digital photography. This results in increasing the dynamic range of the displayed waveform image over simple pixel-by-pixel intensity mapping.
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The present invention relates to data display, and more particularly to a wide dynamic range vector data raster display.
Raster scanned displays, such as CRTs and LCDs, have lower peak brightness than vector scanned CRTs since they have no ability to stop the electron beam at one point. Attempting to display a representation of a complex vector-drawn CRT waveform, typical for live video, on a rasterized display results in losing detail in some parts of the image, usually by clipping the brightest parts.
Currently the display is captured with a source frame buffer where the value of each pixel (address) in the source frame buffer increments every time it is calculated that a hypothetical electron beam representing the waveform would be striking that location. The desired brightness of each displayed target pixel is represented by the value of each address in the source frame buffer. These values may also be decremented with time to represent decay of a CRT. There are two problems: not enough bit depth in each accumulator to capture the full dynamic range for display; and no readily available algorithm for lowering the overall contrast of the display without also lowering the detail and perceived sharpness and clarity of the gray areas of complex waveforms. Only one-dimensional calculations, as shown in
What is desired is the ability to provide a wide dynamic range vector data raster display so a viewer may see subtle detail within all the darkest and lightest parts of an image.
BRIEF SUMMARY OF THE INVENTIONAccordingly the present invention provides a wide dynamic range vector data raster display by using a small matrix of pixels from a source frame buffer containing waveform image data to calculate a value for each pixel on a target display. Any of several algorithms may be used for this transform function, such as the unsharp masking (USM) algorithm used in digital photography. This results in increasing the dynamic range of the displayed waveform image over simple pixel-by-pixel intensity mapping.
The objects, advantages and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawing.
To resolve the problems referenced above, the value for each display target pixel is calculated by an algorithm that uses a matrix of several pixels over a two-dimensional area of a source frame buffer which contains acquired waveform data, as shown in
In photography a 3×3 or 5×5 matrix multiply is typically used to apply a convolutional filter called an “Unsharp Mask” (USM). The counterintuitive phrase “unsharp mask” refers to a traditional photographic process employed to print high dynamic range positive images on paper with limited brightness range. Here a low-contrast, slightly out-of-focus (“unsharp”) negative is made directly from contact printing from the positive film with a sheet of diffusion material between the two and then this low-contrast negative (the “mask”) after development is laid over the positive image. Since the mask is unsharp, it does not reduce the small details but, since it is a negative, it does lower the brightness of the brightest parts while leaving the dark areas unchanged.
An even better and smarter filter algorithm over the simple USM algorithm is described in a SIGGRAPH paper entitled “Gradient Domain High Dynamic Range Compression” by Raanan Fattal et al. Another very effective filter algorithm attempting the same thing is sold commercially for use in Adobe Photoshop software by Applied Science Fiction and called “SHO”.
Thus by using a small matrix of pixel values from the frame buffer to calculate the value for each display target pixel, the dynamic range of the waveform image is increased over simple pixel-by-pixel intensity mapping.
Claims
1. A method of displaying a waveform image with wide dynamic range comprising the steps of:
- acquiring waveform image data in a source frame buffer; and
- convolutional filtering a small matrix of pixels from the source frame buffer to obtain a value for each pixel on a target display.
20040227773 | November 18, 2004 | Hier et al. |
- “Gradient Domain High Dynamic Range Compression” by Raanan Rattal, et al., http://www.cs.hji.ac.il/%7Ewerman/Papers/hdrc.pdf.
- “Image Enhancement via HDR Compression” http://www.cs.huji.ac.il/˜danix/hdr/enhancement.html.
- “High Dynamic Range Compression Results” http://www.cs.huji.ac.il/˜danix/hdr/results.html.
Type: Grant
Filed: May 7, 2004
Date of Patent: Mar 6, 2007
Assignee: Tektronix, Inc. (Beaverton, OR)
Inventor: Kenneth R. Rockwell (Carlsbad, CA)
Primary Examiner: Dan Pihulic
Attorney: Francis I. Gray
Application Number: 10/917,908
International Classification: G06T 11/20 (20060101);