Abstract: Methods and systems for data compression and decompression are disclosed. Specifically, the method for data compression of the present invention receives four inputs representing pixel information of an image and performs a combination of a 4-point discrete cosine transform (DCT) and a weighting function to obtain four outputs representing digital representations of an image. The method for data decompression receives four inputs representing digital representations of an image and performs a combination of an inverse weighting function and a 4-point inverse discrete cosine transform (IDCT) to obtain pixel components of an image. The methods and systems of the present invention may be used in optimizing digital video encoders and decoders.

Abstract: An image sensing element for providing a series of voltage signals corresponding to a two-dimensional image, a two-dimensional analog DCT (discrete cosine transform) circuit for performing a two-dimensional DCT on the voltage signal series from the image sensing element in pixel blocks, and a quantization circuit for quantizing a result of the DCT are provided. The two-dimensional analog DCT circuit is formed of a row of analog sum-of-products arithmetic units for one-dimensional DCT and an analog memory array for matrix transposition. The quantization circuit converts a voltage representing a result of the DCT carried out by the two-dimensional analog DCT circuit into a digital value according to a given quantization coefficient Q=2.sup.N .multidot.S(1.ltoreq.S<2) wherein a voltage S.multidot.Vref that is S times greater than a fixed voltage Vref serves as a reference voltage, and performs a process of right-shifting the digital value N bits in order to provide a quantized digital value.

Abstract: Methods and systems for data compression and decompression are disclosed. Specifically, the method for data compression of the present invention receives eight inputs representing pixel information of an image and performs a combination of an 8-point discrete cosine transform (DCT) and weighting function to obtain eight outputs representing digital representations of an image. The method for data decompression receives eight inputs representing digital representations of an image and performs a combination of an inverse weighting function and an 8-point inverse discrete cosine transform (IDCT) to obtain pixel components of an image. The methods and systems of the present invention may be used in optimizing digital video encoders and decoders.

Abstract: A method and apparatus for compression of data using a technique for quantization and encoding referred to as Mapping through Interval Refinement (MIR). The method uses the size of the original data set together with a target compression ratio to determine the size of a compressed representative of the original data. The data elements after de-correlation are effectively sorted in decreasing order of significance and then written to an output data set using an efficient encoding method which incrementally refines the precision of elements already output. The output process continues until the target compressed file size is reached. Decompression of the compressed data is accomplished by reading in the sorted elements and restoring them to their locations in the data set, and to the precisions saved in the compression process.

Abstract: Method and apparatus for filtering non-text information from a page containing text, the text being associated with a color. The page is represented as an image in a first color space. The image is converted to a second color space that has a color channel closely associated with the text color. The color channel is selected and gray values are derived that correspond to text color channel values associated with cells in the image. Cells in the image having gray values of a predefined relationship with respect to predetermined threshold values are marked as text cells, and the remaining cells are identified as non-text cells. The gray values of the text and non-text cells are adjusted to increase the contrast between text and non-text information. The single-color space image may then be printed by a monochrome printer.

Abstract: A system and method which enables the location and orientation of an image to be determined without introducing scanning artifacts into the rendered image. The system utilizes a separate set of sensors on a scanning bar that are sensitive to a wavelength of light outside the range of wavelengths of the typical sensors found on the scanning bar, such as red, green, or blue. Moreover, the system includes a light source which is capable of emitting the wavelength of light that is outside this range of wavelength of light. Thus, whenever the additional set of sensors detect light, the system would determine that the light was due to a scanning artifact, such as a hole, rip, or dog ear in the original document being scanned.

Abstract: A method and apparatus is provided for efficiently and automatically removing unwanted temporal lighting variations from image sequences. Specifically, temporal light variations from a sequence of images are removed by a process of selecting a reference image (R) and designating a portion of the reference image as a reference image region (M), designating a first portion of at least one base image (F) of the sequence of images as a first selected image region (M') and a second portion as a second selected image region (M"), generating a color mapping by comparing the selected image region of the base image (M') with the reference image region of the reference image frame (M), and applying the color mapping to the second selected image region (M") of the base image (F) to generated a corrected image (F'). Three separate methods of performing the color mapping are disclosed.

Abstract: A method of dynamically quantizing pixel data for use by a digital printer system that prints the pixel data with modulated pixel values. The data is first modulated, with the output pixel values being determined by an image screen. (FIGS. 1 and 2). Then, the data is quantized, using different quantization tables for different pixel values of the same image. The parameters that determine which quantization table is used for a particular pixel value include the pixel's position with respect to the screen or the pixel's image content. (FIGS. 3 and 5) In the case of data that is also being compressed with differential pulse code modulation, the quantization can be based on a buffer fullness measure (FIG. 6).

Abstract: In a method for calibrating a photographic copy printer, developed copies are scanned regionally (such as dotwise), and the measured light transmitted or remitted by each scanned region of the copying material is supplied to a detector array, broken down spectrally, and converted into wavelength- and intensity-dependent measurement data. The electrical measurement signals are digitized, and with their aid, copy-specific measurement data are ascertained. On the basis of the copy-specific measurement data, the original-specific measurement data, and the exposure used in the copying, a model of the original adapted to the copy material and a model for the copy material, or the model (Pi) inverse to it, which forms the basis for calculating the requisite amounts of copying light, are checked with respect to specifiable accuracy criteria and optimized as needed.

Abstract: An encoding apparatus includes an interval register (250), a calculator (208, etc.), means for providing a potential shift-amount (Shift.sub.-- LSZ) of the interval register for the image data in a specific condition (LPS), a shift-amount decision circuit (258), a shift-amount register (259), and a shifter (251). The interval register stores plural bits of interval data to be used for encoding the image data. The calculator updates the interval data in the interval register. The shift-amount decision circuit generates an actual shift-amount of the interval register, in accordance with the potential shift-amount and the output of the calculator. The shift-amount register stores the actual shift-amount, supplied from the shift-amount decision circuit. The shifter shifts the interval data in the interval register a plurality of bits at one time, in accordance with the actual shift-amount stored in the shift-amount register.

Abstract: A method for inspecting a surface of a printing medium, the method comprising the steps of acquiring an image of the surface or a portion thereof, digitizing the acquired image whereby a digitized real representation of the surface or portion is obtained.