Digital image signal processing
AssigneeVideologic Limited
InventorJames Robert Whittaker
Life of this patent
Estimating the term…
Abstract
A raster scanned image may be scaled up or down for display on e.g. a portion of a computer display. This is achieved by dividing the image into a plurality of image cells each with a horizontal width less than that of the whole image. A smoothing algorithm is then applied to the lines of each cell in turn to generate new pixel data in dependence on the scaling operation to be performed. The scaling means stores a number of lines of data from a cell the number being dependent on the particular smoothing algorithm being used. To facilitate scanning of the image cell structure additional sync pulses are generated. These are cell horizontal and cell vertical sync pulses.
Claims15
Digital image signal processing apparatus, comprising:
- an image store for storing an image scanned with a raster of horizontal lines;
- signal processing means for operating on an input image signal to provide an output image signal, each pixel of the output image signal being derived by combining nearby pixels from two or more lines of the input image signal;
- and
- read/write means for reading from the image store a signal to provide an input image signal for the signal processing means and/or for writing the output image signal from the signal processing means to the image store, the read/write means accessing the image store in accordance with a succession of image cells, each cell comprising a fraction only of the horizontal width of the image and a plurality of horizontal lines within that fraction, wherein the read/write means includes means for storing image data for at least one fractional line of an image cell and for less fractional lines than the number of lines that comprise a whole cell dependent on the number of nearby pixels to be combined by the signal processing means.
A method for processing digital image signals comprising the steps of:
- storing an image scanned with a raster of horizontal lines in an image store;
- reading data from the image store by accessing a succession of image cells, each cell comprising a fraction only of the horizontal width of the image store;
- storing at least one line fraction from an image cell and less than the total number of line fractions forming the image cell as a function of the amount of image data required by a predetermined combination algorithm;
- combining nearby pixels from said line fractions of each image cell to produce an output pixel;
- and
- writing said output pixel to the image store.
A method of scaling a raster scanned digital image for display comprising the step of:
- reading image data from an off-screen store which contains the raster scanned image in a succession of image cells, each image cell having a horizontal width smaller than the horizontal width of the raster scanned image;
- storing lines of image data from each image cell, the number of lines stored being at least one and fewer than the total number of lines forming each image cell, the number being dependent on the number required to be simultaneously available to perform a scaling operation;
- combining a plurality of pixel data contained within said stored lines of image data of each image cell, in dependence on the scaling operation, to produce pixel data of an output image;
- writing pixels of the output image to an image display store.
An apparatus for scaling a raster scanned digital image for display comprising:
- a store containing raster scanned digital image data to be scaled;
- means for reading image data from the store as a succession of image cells, each image cell having a horizontal width smaller than the horizontal width of the raster scanned image;
- means for storing lines of image data that form each image cell, the number of image cell lines stored being at least one and fewer than the number of image cell lines forming a complete image cell, the number of image cell lines being stored being dependent on the number of lines required by a scaling operation;
- means for combining image data from a plurality of pixels of each image cell in dependence on the scaling operating performed to produce output pixels of a scaled image;
- display storage means for storing pixels of the output image for display;
- and
- means for writing output pixels to the display storage means.
Dependencies are inferred from the claim text.