Showing papers on "Grayscale published in 1990"

A document skew detection method using run-length encoding and the Hough transform

Abstract: As part of the development of a document image analysis system, a method, based on the Hough transform, was devised for the detection of document skew and interline spacing-necessary parameters for the automatic segmentation of text from graphics. Because the Hough transform is computationally expensive, the amount of data within a document image is reduced through the computation of its horizontal and vertical black runlengths. Histograms of these runlengths are used to determine whether the document is in portrait or landscape orientation. A gray scale burst image is created from the black runlengths that are perpendicular to the text lines by placing the length of the run in the run's bottom-most pixel. By creating a burst image from the original document image, the processing time of the Hough transform can be reduced by a factor of as much as 7.4 for documents with gray-scale images. Because only small runlengths are input to the Hough transform and because the accumulator array is incremented by the runlength associated with a pixel rather than by a factor of 1, the negative effects of noise, black margins, and figures are avoided. Consequently, interline spacing can be determined more accurately. >

Method for detecting and tracking moving objects in a digital image sequence having a stationary background

Abstract: A method for detecting and tracking moving objects in a digital image sequence having a stationary background by comparing the image sequence to a calculated background image sequence, whereby a sequence of binary object masks is calculated whose segments reproduce the shapes and positions of the moving subjects, and whereby the motion vectors of the moving objects are calculated by matching these segments. Also, a sequence of background images is calculated by spatially selective and time recursive averaging of the input image sequence in which the moving objects are not contained but in which other modifications of the background that are not caused by moving objects are contained. Further, a sequence of binary object masks is calculated by binarization of the difference image sequence from the input image sequence and the background image sequence using a threshold whose value is used for controlling the spatial selectivity in the calculation of the background image sequence and whose segments are determined together with their sizes and center of gravity positions. Finally, motion vectors of the detected objects are determined by minimization of the squared gray scale value differences averaged over the intersection of the shifted mask segments, whereby differences between the center of gravity vectors of corresponding segments are utilized as start vectors in the minimization.

Method and system for reproducing monochromatic and color images using ordered dither and error diffusion

Abstract: A method and system for color and monochromatic printing wherein ordered dither and error diffusion processes are combined to provide high quality printed images with good spatial resolution, good gray scale transitions, good low frequency and high frequency responses and a high computational speed. Using this process, gray scale numbers representative of a scanned image are summed for each super pixel of the scanned image and divided by a chosen gray level normalizing factor. This division operation is done to obtain a normalized ordered dither quotient number of drops (dots) to be printed in super pixels and to further obtain an error remainder number of dots to be dispersed to surrounding super pixels. The normalized ordered dither quotient number of dots are printed in pre-assigned individual pixels within printed super pixels, and the error remainder number of drops are diffused to other pre-assigned surrounding or adjacent super pixels. In this manner, a combination of ordered dither and error diffusion signal processing and printing is achieved to simultaneously take advantage of some of the best characteristics of both types of signal processing printing. In color printing, the above operation is carried out in each of a plurality of separate color planes, and all of the quotient information is retained and printed in a predetermined priority sequence for each color plane.

System and method for achieving gray scale DMD operation

Abstract: There is disclosed a system for enhancing resolution of a xerographic process by submodulation of each individual pixel. The submodulation is achieved by anamorphically reducing the square pixel presentation of light rays to a rectangle having a number of controllable segments within each square pixel scan line. By controlling the presentation of light rays to selected segments within each pixel gray scale an enhanced resolution can be achieved.

Gray scales method and circuitry for flat panel graphics display

Abstract: A controller for providing O to N gray scales at a monochrome display. The monochrome display is of the type having an array of pixels energized by a display voltage over time to generate the gray scales. The controller generates a baseline time and uses the baseline time to provide gray scales at the display. In particular, each pixel is energized at least the baseline time for any gray scale above level 0 to reduce flicker in the display. In one embodiment, the baseline time corresponds to a point on the intensity response curve for the display at which the display exhibits a linear intensity response for a given display voltage versus time. In one embodiment, the baseline time is used to generate pixel on/off data to provide gray scales at the display. In yet another embodiment, the baseline time information is used to generate weighted clock information to provide gray scales at the display. In another aspect, the controller includes a plurality of programmable gray scale generators which provide pixel on/off data, weighted clock information, and black/white pixel data to provide gray scales at the display. One of the gray scale generators is selected and programmed depending on the identity of the display device.

Method and system in video image reproduction

Abstract: A system and method for the accurate reproduction of the tone and luminance of a first video monitor screen includes, in one embodiment, a first video monitor and a second video monitor, each with a CRT screen. A gray scale test pattern is shown on both screens. The test pattern on each screen is measured using a spot photometer and the results are entered into a computer memory look-up table and compared, a tone-by-tone basis. A set of corrections is obtained for each tone of the gray scale. Those compensating corrections are used to adjust the luminance, on a pixel-by-pixel basis, of the second video screen of the second video monitor, so that the second screen is compensated to produce a gray scale which reproduces the tone and luminance values of the gray scale on the first screen.

Determination of ambient light level changes in visual images

Abstract: A visual image comparison method is provided, including the steps of: obtaining a first digital representation of a first visual image, where the first digital representation comprises a first plurality of pixels, and each pixel has a gray scale indicative of light intensity; obtaining a second digital representation of a second visual image, where the second digital representation comprises a second plurality of pixels, and each pixel has a gray scale indicative of light intensity; and selectively making a first predetermined number of comparisons of corresponding pixels from the first and second digital representations to determine whether a difference in ambient light intensity exists between the first and second visual images, and, selectively making a second predetermined number of comparisons of corresponding pixels from the first and second digital representations if and only if no difference in ambient light intensity exists between the first and second visual images, and indicating an alarm condition when a percentage of the second predetermined number of comparisons result in pixels having a difference in gray scale of a predetermined amount. Apparatus is also described for the purpose of implementing the method.

Image inputting device for endoscope

Abstract: An image inputting device for an endoscope is provided in which image obtained by the endoscope and decomposed into a plurality of color signals is converted into electrical signals. A gray scale correcting section having an adjustable correcting value is provided for each of the plurality of color signals. In consequence, the gray scales of the plurality of color signals can be separately and adjustably corrected, and a resolution which corresponds to the luminance level of each color can be set so as to enable effective information to be easily obtained from all wavelength regions.

Method and system for printing in one or more color planes with improved control of error diffusion

Abstract: A pixel assignment and error diffusion system and method of gray scale printing in one or more color planes in the fields of ink jet printing, electrophotographic printing, or the like. The direction of each error diffusion with respect to (28) the location of a just-scanned or just-processed super pixel (28) within a larger scanned area is controlled by the contemporaneously developing gray scale profile and gradient over a previously scanned area defined by a predetermined number of previously scanned super pixels (28-44). This developing gray scale (116, 118, 120, 122) profile and gradient of a scanned image is used to select a matching error diffusion set (E) of diffusion points, each having a relative weight W and a location L, from a chosen look-up table stored in memory (98). The relative weight W is proportional to the gray level intensity of the developing profile (116, 118, 120, 122) and the location L is proportional to the slope of the gradient of a family of gray level profile or contour lines (104, 108, 112), wherein the gradient is generally perpendicular to these lines. The selected error diffusion set (E) is in turn used to control the direction and weighted distribution of an error remainder value R into areas of a processed image adjacent each just-scanned or just-processed super pixel (28-44) within a larger scanned area.

Real time physician view box

Abstract: A medical diagnostic imager (10) reconstructs (96) raw scan data into digital image representations which are stored in a mass storage memory (46) such as DRAM or disk. As the scanner reconstructs the series of images, each digital representation image is transferred to an image VRAM (100) into one of a plurality of selected image areas. A video monitor (24) displays the electronic image representations from the image VRAM in the selected pattern of images, e.g. a 4×3 grid of images. The digital image representations are transferred to the image VRAM and displayed on the video monitor as they are generated such that the monitor displays the previously generated images and the most recently generated image as it develops during the reconstruction process. The diagnosing physician selects (104) one of the images and selectively adjusts (110) the window and level of its gray scale. After each of the images has been independently designated and its gray scale independently adjusted, one or more of the adjusted electronic image representations are transferred to a film printer (32) which makes a hard copy film print of the selected image(s). A graphics control (122) and a keyboard (132) enter data into a graphics VRAM (120) and a text VRAM (130), respectively. The electronic diagnostic image, graphics, and text data are merged (138) such that the graphics and text are superimposed on selected portions of the displayed video images.

System and method for automatic image saturation, gamma, and exposure correction in a digitizing video capture system

Abstract: Analog video data input is received by a video capture system and digitized. From the pels of the captured image, a gray scale level histogram is constructed with the system processor, and normalized to established white-black references similar to the contrast control function at image capture time. Peaks likely attributable to image artifacts are limited. The image processor then performs a second order best fit regression of the histogram from which the image is thereafter corrected. An automatic correction of the image contrast is thereby effected, wherein capture artifacts are reduced while retaining those of the image. In an alternate embodiment, instead of limiting peaks, an iterative best fit is performed, wherein the peaks are weighted in a subsequent best fit pass as a function of their distances from the curve fit from a prior best fit pass.

Edge enhancement error diffusion thresholding for document images

Abstract: Apparatus for converting multilevel video images into a bilevel image having an accurate rendition of the original grayscale of the image. The apparatus performs enhanced preservation of edge information in the image when using error diffusion techniques.

Optical scanner threshold setting method and sheet

Abstract: A method for the optimization of optical scanners by automatically determining image processing threshold values using a novel threshold calibration sheet. The calibration sheet image has lines at a forty-five degree angle to the path of the document through the scanner and has a predetermined image dot count. One embodiment comprises the steps of repetitively scanning the sheet until scanner threshold values which satisfy predetermined relationships with said dot count are determined. Another embodiment comprises the steps of a single calibration scan with multiple processing of the gray scale scan data on a host computer. By using this method, two or more scanner cameras can work together on processing document images and consistently give uniform results, independent of their individual technical operating or performance differences.

Method for analyzing a body tissue ultrasound image

Abstract: A method and device for interpreting and processing medical ultrasound and other video images. The mix of reflection coefficients in pixel windows is measured by determining the range and distribution of pixel gray scale values to establish "echoic texture" characteristics. These characteristics are compared with corresponding characteristics of known tissues. The degree of correlation allows a prediction of tissue characteristics of the examined window.

Method of coding image segments of any shape

Abstract: A method of coding digital image data of an original image for transmission and reproduction. The original image is subdivided into partial image regions whose shapes are adapted to local image structures. For each partial image region, a set of two-dimensional, lineraly independent basis functions is provided. The areal expanse of the basis functions approximately corresponds to the size of a rectangle circumscribing the partial image region to be coded and the raster of the sampled values of the basis functions corresponds to the pixel raster of the original image. The sampled values of the basis functions disposed within the area defined by the partial image region are orthogonalized in order to obtain a set of new, orthogonal basis functions, with the set including as many orthogonal basis functions as there are pixels within the partial image region. Coefficients of the orthogonalized basis functions describing the partial image region are then calculated. The coefficients correspond to the rectangular image regions in the partial image region and represent the gray scale values of the partial image region and thus an approximation of the original image. In a preferred embodiment, the contour of the partial image region is coded and transmitted along with the coefficients to a receiving location, where the orthogonal basis functions are generated based on the contour and the image is reproduced with the orthogonal basis functions and the coefficients.

Gray scale system for visual displays

Abstract: An image is projected in gray scale on a large screen without any flicker, the different colors or shades being indicated on the screen by individual shades of gray. The image is defined by a plurality of pixels which are raster scanned. At each pixel position, a plurality of first digital signals are generated each representing an individual primary color (e.g. red, green and blue) or shade in the image at the position. Second digital signals individually representing such different colors or shades are also produced on a pseudo-random basis -e.g. by producing video clocked signals not only at the pixel positions but also during the horizontal and vertical retraces. The second signals are repetitively counted to a particular value to correspond to successive frames in the video image. In each successive frame, the first signals are compared in value with the second signals at each individual pixel position. A video signal is produced for generating the image for that pixel on the large screen only when the first signals for each pixel in a raster scan have a greater digital significance than, or an equal significance to, the second signals for that pixel in that raster scan. In each repetive count of frames to the particular value, a video signal is produced for each pixel in a number of frames dependent upon the digital significance of the first digital signals for that pixel. However, such video signals are produced for each pixel in a different pattern in each repetitive count to the particular value so as to eliminate any flicker in the video image on the large screen for that pixel.

Duty cycle technique for a non-gray scale anti-aliasing method for laser printers

Abstract: A non-gray scale anti-aliasing method for smoothing one or more edges of an image to be printed by a binary imaging printer. The image is generated by rasterizing an ideal outline of the image using a processor means for processing a plurality of raster lines to form a pixel representation of the image to be communicated to the binary imaging printer. An ideal fill area representing the area inside the ideal outline for the pixel currently being processed is determined for each pixel in the raster line and then compared to at least a first and second comparison value. Based upon the comparison, a determination is made as to whether the pixel currently being processed will be turned on or turned off. In one embodiment, the comparison is made by the use of a lookup table having a set of predetermined comparison values that contain estimated fill values used by an accumulator to determine whether to selectively modify the pixel. In a different embodiment, the lookup table is replaced by using a fill function for translating the ideal fill value into the estimated fill value. In another embodiment, a control signal having a predetermined duty cycle is generated for all pixels within a boundary transition range defined by the first and second comparison values.

Non-gray scale anti-aliasing method for laser printers

Abstract: A non-gray scale anti-aliasing method for smoothing the horizontal components of the edges of an image to be printed by a laser printer having unequal pixel resolutions in the horizontal and vertical dimensions is accomplished by selectively modifying the on and off states of pixels on either side of each vertical transition point along the horizontal components of raster lines representing the edges of the pixel representation of the image. A processor is provided with an ideal outline of the image and rasterizes the ideal outline of the image to determine which pixels to turn on and which pixels to turn off in a frame buffer that stores a pixel representation of the image to be printed by the laser printer. The modified pixel representation in the frame buffer is then communicated to the laser printer such that the laser printer may print the smoothed image.

Variable block-sized vector quantization of grayscale images with unconstrained tiling

Abstract: The design and performance evaluation of a variable block-sized vector quantizer with unconstrained tiling (UTVQ) is discussed. The coder segments the input image into an unconstrained tiling of variously-sized, nonoverlapping rectangular regions, each of which is then coded with a vector quantizer. UTVQ is compared with the more constrained quadtree vector quantizer (QTVQ) approach. A transmission scheme which reduces the overhead required to convey UTVQ segmentation geometry is developed. Several UTVQ segmentation strategies are explored, and mean-residual codebooks with appropriate side-stream compression techniques are developed. The projected rate and rate-distortion figures indicate that the UTVQ system outperforms the QTVQ system under typical conditions. >

Adaptive error diffusion thresholding for document images

Abstract: Apparatus for converting multilevel video images into a bilevel image having an accurate rendition of the original grayscale of the image. The apparatus can provide an improved rendition of low contrast images.

Line rasterization technique for a non-gray scale anti-aliasing method for laser printers

Abstract: A line rasterization technique for a non-gray scale anti-aliasing method smoothes the edges of a single pixel width line image to be printed by a binary imaging printer. The line image is generated by rasterizing an ideal line image as a plurality of raster lines to form a pixel representation of the line image to be communicated to the binary imaging printer. For each vertical transition point created by the ideal line image crossing two adjacent raster lines, the present invention smooths the line image by selectively modifying the on and off states of one or more pixels in an adjacent raster line on either side of the vertical transition point. The pixel representation of the line image is then communicated to the printer such that the printer may print the smoothed line image.

Integrated displays of multiparameter and multimodality images

Abstract: Two specific approaches to integrated displays of multiparameter and multimodality tomographic images are proposed and illustrated. Such integration enables the radiologist to see the combined information that these displays only crudely afford when viewed individually. With color coding, the gray-scale values of the pixels in the separate images control the color values of corresponding pixels in a single color picture. With geometric coding, the gray-scale values from the separate images control the geometry of a graphic icon at corresponding locations in the combined image. These techniques are applies to create integrated displays of two-parameter magnetic resonance images of two medical cases. >

Unification of image segmentation and edge detection

Abstract: A method of simultaneous image segmentation and edge detection based on grey-level co-occurrence matrices is described. An analysis of the distributions within a co-occurrence matrix defines an initial pixel classification into both region and interior or boundary classes. Local consistency of pixel classification is enforced by minimising the entropy of local region and boundary information, where region information is expressed by conditional probabilities, estimated from the co-occurrence matrices, and boundary information by conditional probabilities which are determined a priori. The method robustly segments an image into homogeneous areas and generates an edge map. The technique extends easily to general edge operators; examples are given of the techniques applied to both synthetic and infrared imagery for the [1 –1] and Canny edge operators. The results are compared with other techniques.

Texture segmentation using directional operators

Abstract: A method for the classification and segmentation of texture in images is presented. The method derives texture features from the image which are independent of mean gray-scale level but dependent on texture orientation. Each pixel in the original image can then be classified using supervised pattern-recognition techniques. A segmentation of the image can be produced by delineating the boundaries within the classified image in horizontal and vertical directions. The algorithm is efficient and can be implemented using general or specialist processors. Results from a sidescan sonar image of a sea bed and a video image containing samples of real texture are given. >

Acousto-optic image correlator with a throughput rate of 1000 templates per second

Abstract: A two dimensional image correlator based on acousto-optic (AO) and charge coupled devices (CCDs) is described that can be built with existing technology to provide 1000 frames per second operation. In recent years, architectures have been developed that perform the two dimensional correlation utilizing one dimensional input devices. The input scene is loaded into the acousto-optic device (AOD) one line at time. This line is then correlated against all of the rows of a reference template introduced into the optical system using a one dimensional array of LEDs or laser diodes. However, it generally takes a much greater time to load the AO cell than it does to process the information. This latency time severely limits the maximum throughput rate of the processor. This paper introduces a new acousto-optic correlator implementation that overcomes this bottleneck so that processing can occur close to 100% of the time. A grayscale image correlator is proposed that can be built using present technology that can realistically achieve throughput rates on the order of lO12 operations per second. This translates to over 1000 correlations per second for input scenes with dimensions of 512 x 512 pixels and reference templates of size 64 x 64 pixels.

A priori information in image analysis: assessment of intensity distribution for definition of shape and size of small vessels

Abstract: A method for incorporating prior information in computer-based image analysis is described and critically evaluated. The specific application improves pixel resolution (spot size) and shape estimation of small vessel cross sections in exchange for dynamic range information. The potential subpixel spot size sensitivity for a 16-bit gray scale is better than one part in 32000. The performance of shape recovery is assessed in relation to signal-to-noise ratio, acquired image resolution, vessel shape complexity and aspect ratio. The process is shown to be effective and stable when the signal-to-noise ratio exceeds 10, when the number of pixels across the vessel is two or more, when the vessel contour has as many as six lobes, and when the aspect ratio is in the range 0.2-5.0. >