Abstract: A color correction apparatus and method in which a mask is derived from image data in a first pixel representation and is used to convert the image data into a perceptual color space representation which is a function of a background luminance parameter. The mask corresponds to a blurred monochrome version of the original image and includes a set of averaged greyscale values having a pixel-by-pixel correspondence with the original image. The values within the mask vary dependent on the location of the corresponding pixel within the image data. When converting the image data pixel-by-pixel into the perceptual color space representation, localized color correction is obtained by using varying mask values as the background luminance parameter for each pixel conversion.

Abstract: A method of processing an image includes the step of transforming spatial image data to generate a first set of frequency domain basis coefficients. The first set of basis coefficients is combined with a second set of basis coefficients corresponding to a frequency domain transform of a pre-determined halftone texture. In various embodiments, the forward transform is a selected one of the discrete cosine transform, the discrete sine transform, and the Fourier transform. The combined basis coefficients are quantized and entropy encoded to generate the compressed image data. After any necessary decompression, an inverse transform may be subsequently performed to reconstruct the source spatial image with the pre-determined halftone texture. In one embodiment, a method of processing a source image includes the step of scanning the source image to generate digitized spatial image data. The digitized data is subdivided into a plurality of blocks.

Abstract: A method for calibrating a display using a plurality of visual stimuli. A plurality of visual stimuli having an associated digital count and an associated position are displayed. The digital count of each of the visual stimuli are adjusted wherein the plurality of visual stimuli are ordered and there are perceived lightness differences between the visual stimuli. An offset is estimated based on the digital count and the position of the visual stimuli. A gain is estimated based on the offset. A gamma is estimated based on the gain, the offset, the digital count and an estimate of luminance of the visual stimuli. An average gamma is estimated by determining the average value of the gamma for the plurality of visual stimuli. In one embodiment, the visual stimuli are a series of patches positioned in a row, each patch of having a pre-assigned gray level and having a visual control to lighten or darken the visual stimuli, wherein the gray level corresponds to the digital count.

Abstract: An input image represented by a set of input pixel values is color-corrected by locally modifying the input pixel values according to pixel neighborhoods; and determining an output image having a set of output pixel values. Each set of output pixel values equals a non-linear combination of a set of input pixel values and its corresponding set of modified pixel values.

Abstract: An inkjet printing system uses high-resolution printheads holding different color inks to produce true 600 dpi color printing with a single pass of the printheads. By achieving a smaller drop size in the range of 25-50 picoliters for each printhead having a separate ink color (yellow, cyan, magenta, black), a full range of high-resolution color print-quality modes is possible. In an exemplary embodiment with a carriage scan speed of 25 ips, a two-pass draft mode uses a 7.5 kHz firing frequency, a four-pass normal mode uses a 4 kHz firing frequency, and an eight-pass best mode uses a 2 kHz firing frequency. In all of these print modes, each printhead can provide color inkdrop placement on every pixel row during a single pass.

Abstract: Color inkdrops form on a print medium in at least partly overlapping swaths. Apparatus holds and provides--or generates in real time--data defining a generally randomized printmask, which is applied to control working parts of an inkjet printer. Preferably the apparatus establishes an elemental pixel subgrid of rows and columns, used in determining inking patterns essentially throughout the image; and stores in the pixel subgrid a previously generated, generally randomized selection of pixel columns for printing of an inkdrop, in each subgrid pixel row--and conversely an analogous selection of pixel rows for printing a drop in each subgrid pixel column. Also preferably the generally randomized selection is subjected to location rules as to pixels above and to at least one side of each pixel. Numerous specific masks are specified as pass-number patterns, including an eight-by-eight "knight" array, two sixteen-by-five arrays, a sixteen-by-ten array, and several four-by-four arrays.