Abstract: A method of stroking a curved path with a fill of pre-determined thickness, where the path has line segments defined by a number of points, the method being performed by forming a number of projection lines normal to the curved path at the points, where each of the projection lines has a length based on the fill thickness, determining an intersection between a set of the projection lines, the intersection indicating the occurrence of a void in stroking the curved path, and then constructing one or more polygons filling in the void in the stroked path.

Abstract: A method of stroking a curved path with a fill of pre-determined thickness, said path having line segments defined by a plurality of points, said method comprising the steps of: forming a plurality of projection lines normal to the curved path at the plurality of points, each of the projection lines having a length based on the pre-determined fill thickness; determining an intersection between a set of the plurality of projection lines, said intersection indicating an occurrence of a void in stroking the curved path; and in response to detecting said intersection of the set of projection lines, constructing at least one polygon filling in the void in the stroked path.

Abstract: Methods, apparatuses, and computer program products for rendering a piece-wise smooth image are disclosed. The image is specified by image values along opposite sides of paths. The paths are converted to chains of straight line segments, and image values are set for each side of each segment. Coefficients are determined for each line segment. A first coefficient for each segment is based on a difference between specified image values on opposite sides of the segment. A second coefficient for each segment is obtained using an average of image values on opposite sides of the segment and a system of linear equations. Each image value is calculated as the addition of a sum over all segments of the product of first coefficient for a segment with a dipole field value for the segment and a sum over all segments of the product of second coefficient for a segment with a logarithmic field value for the segment.

Abstract: A Hybrid Compressor and method of compressing a tile of pixels within an image are disclosed. An Edge Processor of the Hybrid Compressor analyzes pixel runs of the tile and generates boundary data defining one or more regions comprising pixels of substantially identical color. A Palette Processor of the Hybrid Compressor generates data defining a color value for each region. An Image Processor of the Hybrid Compressor generates a representation of pixels not included in the one or more regions.

Abstract: A method (200, 400) of compressing an input image (201) is described. The method (200, 400) starts by extracting image gradient data representing pixel differences along contours of the image. Next, the method forms an edge based image from the image gradient data and a low resolution image derived from the input image. The method then computes a residual image representing a difference between the edge based image and the input image, and finally compresses the input image by encoding the image gradient data, the low resolution image, and the residual image.

Abstract: A method of determining a quality value for an image frame is disclosed. The method comprises dividing (in a step 202) the frame into a plurality of tiles (906) and determining attributes (in a step 206) of each said tile based upon pixel values of the tile, and pixel values of a corresponding tile of a preceding frame. The method then establishes (in steps 210, 212) the quality value of the frame by testing the tile attributes of the frame against pre-determined criteria. The method then defines (in a step 220) the quality value of the frame depending upon results of the testing.

Abstract: A method (200, 400) of compressing an input image (201) is described. The method (200, 400) starts by extracting image gradient data representing pixel differences along contours of the image. Next, the method forms an edge based image from the image gradient data and a low resolution image derived from the input image. The method then computes a residual image representing a difference between the edge based image and the input image, and finally compresses the input image by encoding the image gradient data, the low resolution image, and the residual image.

Abstract: A Hybrid Compressor (304) and method (500) of compressing a tile (2200) of pixels within an image are disclosed. An Edge Processor (404) of the Hybrid Compressor (304) analyses pixel runs (403) of the tile (2200) and generates boundary data defining one or more regions comprising pixels of substantially identical colour. A Palette Processor (411) of the Hybrid Compressor (304) generates data defining a colour value for each region. An Image Processor (416) of the Hybrid Compressor (304) generates a representation of pixels not included in the one or more regions.

Abstract: An image recording apparatus (2000) is disclosed, which comprises forming elements (2002) for forming an image, a memory (2006) indicating relative desirability of utilising the forming elements (2002) for forming the image, and processing means (2008) for computing image recording signals using input image signals (2012) and the stored data. The use of a particular forming element is thereby biased dependent upon the relative desirability data of other forming elements, the corresponding input signal for the particular forming element, and a term for the particular forming element.

Abstract: An apparatus (1100) for halftoning an image is disclosed. The apparatus comprises means for determining an output value of a current pixel on a current scanline using a sum of an input value (1102) for the current pixel and a neighborhood error value (1150) at the current pixel, means (1124) for determining an error at the current pixel as the difference between (i) the sum of the input value (1102) for the current pixel and the neighborhood error value (1150) at the current pixel, and (ii) the output value (1120) of the current pixel; and means (1140) for adding a proportion of the error at the current pixel to neighborhood error values at as yet unprocessed pixels of a subsequent scanline in accordance with a next scanline error impulse response; wherein said next scanline error impulse response approximates a function which spreads with self-convolution in proportion to a degree of self-convolution.

Abstract: Methods and apparatus for processing an image is disclosed. First an output value of a first current pixel (inx,y−1), which is not at an edge of the image, is determined using a first influence value (Wx,y−2) for a first current pixel which equals a first sum, over a first set of pixels, of the product of a pixel weight value and a corresponding pixel value, where the pixel weight value is substantially equal to a weight factor (X, Z) raised to the power (i) of the distance of the pixel from the first current pixel.

Abstract: A method of halftoning input image data intended for reproduction on a display (114) having a plurality of pixels (23-27) and a limited pixel response time (see FIG. 1) is disclosed. In a first halftone cycle (K=n), the method comprises (first) halftoning an input value (30) to display an extreme representable (100% or 0%). In a second halftone cycle (K=n+1), (second) halftoning the input value (30) to display an intermediate value such that the average of the extreme representable value and the intermediate value is substantially equal to the input value.

Abstract: An apparatus (1100) for halftoning an image is disclosed. The apparatus comprises means for determining an output value of a current pixel on a current scanline using a sum of an input value (1102) for the current pixel and a neighborhood error value (1150) at the current pixel, means (1124) for determining an error at the current pixel as the difference between (i) the sum of the input value (1102) for the current pixel and the neighborhood error value (1150) at the current pixel, and (ii) the output value (1120) of the current pixel; and means (1140) for adding a proportion of the error at the current pixel to neighborhood error values at as yet unprocessed pixels of a subsequent scanline in accordance with a next scanline error impulse response; wherein said next scanline error impulse response approximates a function which spreads with self-convolution in proportion to a degree of self-convolution.

Abstract: An image recording apparatus (2000) is disclosed, which comprises forming elements (2002) for forming an image, a memory (2006) indicating relative desirability of utilising the forming elements (2002) for forming the image, and processing means (2008) for computing image recording signals using input image signals (2012) and the stored data. The use of a particular forming element is thereby biased dependent upon the relative desirability data of other forming elements, the corresponding input signal for the particular forming element, and a term for the particular forming element.

Abstract: A method and apparatus are disclosed which permit a seamless halftoning of an image by halftoning regions of the image independently and/or in parallel. Each region of the image being arbitrarily determined, and being halftoned on the basis of halftoned pixel results of pixels within a predetermined neighborhood of the region. The arrangement providing a greater flexibility in the independent halftoning of the regions, while providing substantially seamless joins between abutting halftoned regions of the image. Further, the arrangement also provides a mechanism for parallel processing (halftoning) of abutting regions of an image with substantially seamless results.

Abstract: A method and apparatus are disclosed which permit halftoning of pixels in an image based upon the relative repulsive forces between a current pixel being halftoned and preferably all previous pixels that have been halftoned. Such arrangements give improved halftoned image quality, at least for some images, compared to that obtained from error diffusion or dithering.

Abstract: An image processing system in which a computer image is halftoned by halftoning a current pixel using error diffusion, with a halftoned output value of the current pixel being determined using errors derived from substantially all previously halftoned pixels of the image. Output error values are determined for each pixel, and are acted upon by an error diffusion mask of geometrically reducing values. In certain instances, previously halftoned pixels are divided into two or more groups to obtain a desired contribution from previously halftoned pixels.