Abstract: A method and apparatus for compressing digital data defining the colour component content of pixels of a coloured image, the apparatus comprises a processor (1) for performing a principal component analysis on each of a number of non-overlapping blocks of pixels making up the image to determine the principal component vectors corresponding to the block; for rounding the principal component vectors to a fixed set of intervals; for transforming the original pixel data into the colour space defined by the rounded principal component vectors; for performing a compression algorithm on the transformed pixel data; and for performing a separate compression algorithm on the rounded principal component vector values.

Abstract: A digital image processing system comprises a processor at a central, first site; and digital image processing equipment such as an analyze scanner and an expose scanner at a second site remote from the first site. The processor and the digital image processing equipment are connectable and are adapted to pass signals therebetween corresponding to signals generated by the digital image processing equipment. These signals may be representative of operator commands or digital data generated at the second site which can be monitored at the first site.

Abstract: A scanner comprises apparatus for scanning an image in a series of scanlines with a beam. Beam splitters split the modulated beam into a number of subsidiary beams which are fed to respective detectors. In one example (FIG. 2), a set of masks are provided to divide the subsidiary beam spatially such that different portions of the beams are fed to respective detectors. In another example (FIG. 4 ), a color filter splits the modulated beam into its respective color components and, after this beam has been split into subsidiary beams, the individual color components are filtered by filters and fed to detectors.

Abstract: Image handling apparatus comprises a store (22) for storing digital data defining an image; a monitor (30) connected to the store for displaying the image; a control system (1,2) for controlling the image display; and a digitizing tablet (5) defining an area corresponding to the area of the image displayed on the monitor (30) and a pen (31) moveable across the tablet (5). The control system (1,2) is responsive to movement of the pen (31) beyond the monitor display defining area of the tablet (5) to change the manner in which the image is displayed (e.g. scroll, zoom etc.

Abstract: Image scanning apparatus comprises a radiation source to generate a radiation beam, a support on which an original image is mounted in use so that the radiation beam is incident, in use, on the original image, the support and the beam being continuously movable relative to one another in a cyclic manner to expose successive scan lines on the original image. A detector is provided for detecting the radiation beam after exposure to the original image. A buffer receives image signals corresponding to a valid scan line of the original image at a first rate from the detector during exposure of the scan line and outputs all the image signals corresponding to a valid scan line at a second slower rate to a processor within one cycle of the relative motion between the support and the radiation beam. The buffer is prevented from storing signals from the detector when a valid scan line of the original image is not being exposed.

Abstract: An assembly that can be optically scanned and that comprises a transparency that includes an image and that is carried by a transparent support to which it is secured and with which it is in intimate fluid contact wherein the fluid contact is provided by an overall layer of pressure sensitive adhesive that has a refractive index substantially the same as the refractive index of the transparency and that releasably secures the transparency to the support.

Abstract: A method of displaying a selected section of an N-dimensional color space uses two memories (14,16). The first memory (14) stores memory addresses of the second (16). The second memory (16) stores data defining color at addresses corresponding to the selected section and background color at all other addresses. The defined colors and background are output to a display (11) so that the background areas blend with the existing background and only the color of the selected section is redrawn not the whole image.

Abstract: A graphics system comprises an input device, and a computer for detecting changes in the position of the input device relative to a surface, and a monitor (63) for displaying patterns which follow the movement of the input device. The computer calculates at least one differential derivative with respect to time of the input device position and controls characteristics of the display patterns in dependance upon the or each calculated derivative.

Abstract: A method and apparatus for generating an electronic representation of a boundary, particularly for use in generating an outline around a displayed image. The apparatus comprises a screen (30) and a control system (1,2). The control system enables a cursor to be moved to spaced points along the boundary and determines the coordinates of the boundary by interpolating straight lines between adjacent points. The control system also permits at least part of the boundary to be defined in a continuous drawing mode in which the cursor is moved continuously along the boundary, the coordinates of the successive cursor positions being determined.

Abstract: An apparatus for controlling the exposure of a record medium (4) to a radiation beam (3) during relative scanning movement between the medium and the beam to record half-tone image separations at particular screen angles, includes a control signal generator (6); a controller (8,9); and a store (7) for storing a previously generated half-tone dot map under the control of the controller (9), the control signal generator being responsive to an image signal representing the color content of an image and a signal from the store to generate a binary beam control signal by scanning the map in synchronism with the beam scanning the record medium and comparing the image signal with the current map value, the binary beam control signal being generated in accordance with the result of the comparison. The store (7) is of a size sufficient to enable the half-tone dot map to define a number of adjacent half-tone dot areas, each area corresponding to a half-tone dot and the content of at least some areas being different.

Abstract: A method of generating a representation of a subsidiary colored image initially contained within a color content of pixels of the image comprises defining a control data array. This control data array (9) defines, for at least those pixels in the image corresponding to the region containing the subsidiary image, the proportion of the image pixel color which is due to the subsidiary image. The average color in regions of the image different from the subsidiary image region is then determined. The inverse of the control data array is multiplied by the determined average color to generate a background image (13) which is subtracted (14) from the corresponding region of the original image so as to generate the representation of the subsidiary image.

Abstract: An apparatus for electronically modifying the appearance of an image stored in the form of digital data defining the color content of the image comprises a store (8) for storing sets of coordinates defining positions around the edge of the image and, for each set of coordinates, storing the characteristics of an electronic painting tool including the profile of the tool. A monitor (30) displays the image. A processor (1, 15-19) compares the current position of the tool with the sets of stored coordinates and when the tool is at or in the region of a set of stored coordinates changes the tool characteristics to those previously determined for that set of coordinates.

Abstract: Apparatus for creating or modifying an electronically represented image comprising a display (30); a store (11) for storing arrays of data values defining electronic brushes; an input device (5) to enable an operator to control movement of a previously defined brush on the display; and a processor (1) responsive to the input device (5) to move an electronic brush selected from the store across the displays (30) so as to create or modify an electronically represented image. The processor (1) is also adapted to generate and store a representation of the profile of an electronic brush for use subsequently to create or modify electronically an image, in which a previously defined brush is used to define an array of pixels at a first resolution having a shape corresponding to the new brush, the previously defined brush comprising an array of pixels for each of which a value is stored.

Abstract: Apparatus for assembling images together in which each image is defined by respective pluralities of sets of data values, each set corresponding to a group of pixels of the image, the groups being arranged in a regular array across the image whereby the sets of data values can be obtained from sets of first data each defining the color content of an image pixel in the group. The apparatus comprises a control system for determining the position of a first image relative to a second image in a desired assembled image; an assembled image store; and a modified image store. The control system is operable to convert the sets of data values of the overlapping groups of pixels defining a region of the assembled images which overlaps and which is to be retouched into the corresponding sets of first data, consolidating the converted sets of first data into an assembled set of data, modifying the assembled set of data as desired, and storing the modified, assembled data set in the modified image store.

Abstract: A method of simulating airbrushing of an image electronically comprises generating a set of pixel values from a stored set. The pixels define the area of an airbrush and the color content is modified by selecting sets in sequence, then combining the image pixel content with the pixel value and a unit amount of brush color. The pixel values are generated by dividing the sequence into sets and recording the number of occurrences of each pixel coordinate in a set. The brush may be a single color or contain pixels of many different colors when defined by another image.

Abstract: A method for generating a binary representation of an image represented in half-tone form is described in which the image is scanned and sampled, and in which each pixel corresponding to a sample of the image is assigned one of two colors. The method comprises, for each group of abutting and non-overlapping sampled pixels, determining the number of pixels in the group which are to be assigned to each of the two colors (step 13); allocating a unique sequence to the pixels (step 15); and assigning one of the two colors to pixels in sequential order until the predetermined number of pixels of that color has been assigned (step 16) and thereafter assigning the other color to the remaining pixels in the group (step 17).

Abstract: Apparatus for interactively modifying an image represented by digital data defining the color content of pixels in the image in terms of color components defining a first color space comprises a store (1) for storing the original image; a look-up table (2) for transforming the image into a second color space (LCH) and a store (3) for storing the second color space representation. The second color space is defined by second color components having a reduced resolution relative to those of the first color space. The representation in the second color space is fed through a look-up table (4) whose contents can be controlled by an operator so that the image at low color resolution can be retouched interactively, the retouch version being displayed on a monitor (6). Once a satisfactory retouch has been achieved, the original image in the store (1) is modified and stored in the first color space in a store (13).

Abstract: Apparatus for generating an array of control data, the array having a number of pixels each of which corresponds to a respective pixel in an image, the apparatus comprising a first store (100) for storing the image data; a second store (17) for storing the control data; and a processor which, for each control data array pixel generates and stores in the second store (17) a control value in accordance with a predetermined algorithm which defines the control value as a function of the corresponding image pixel color components and the corresponding color component(s) of the target colors, wherein the generated control values can be ordered on a scale of at least three value classes.

Abstract: A color display control system for use with a display (1) having a screen (2) capable of being activated so as to generate at least two colors. The system comprises at least one optical sensor (4,5) which detects optical radiation emitted from the display screen (2). A control system (10,11,13) is provided which is responsive to an output signal from the or each sensor (4,5) related to the intensity of the detected radiation to control the optical characteristics of the display so that the detected color is generated in a predetermined manner.

Abstract: A method of compressing digital image or image-like pixel data. The method comprises carrying out the following steps on small blocks of pixels:a) determining the differences between digital values of adjacent pixels in the block to define respective link weights;b) determining a tree connecting all the pixels in the block such that the sum of the link weights in the tree is a minimum;c) dividing the tree into segments by removing links with weights greater than a threshold value, so dividing the block into segments of linked pixels;d) generating a segmented representation of the block by setting the values of all pixels in each segment to a single, respective, representational value; ande) compressing the segmented representation to generate compressed data.