Abstract: A method and system for transparently failing over a legacy application from a first system to a second system of a server cluster by tracking and checkpointing changes to application configuration information stored in a system's local registry. When an application running on the first system makes a change to the application configuration information in a subtree of the registry, the change is detected and a snapshot of the subtree's data is taken. The snapshot is written to a storage device shared by systems of the cluster, such as a quorum disk. When the application is failed over to a second system, the snapshot for that application is retrieved from the quorum disk and written to the registry of the second system in a corresponding subtree. The application is then run on the second system using the most-recent application configuration information as modified by the other system in the cluster.

Abstract: A method and system for transparently failing over a legacy application from a first system to a second system of a server cluster by tracking and checkpointing changes to application configuration information stored in a system's local registry. When an application running on the first system makes a change to the application configuration information in a subtree of the registry, the change is detected and a snapshot of the subtree's data is taken. The snapshot is written to a storage device shared by systems of the cluster, such as a quorum disk. When the application is failed over to a second system, the snapshot for that application is retrieved from the quorum disk and written to the registry of the second system in a corresponding subtree. The application is then run on the second system using the most-recent application configuration information as modified by the other system in the cluster.

Abstract: A method and system for communicating modification information to servers in a server cluster. Local changes, such as modifications to a resource requested at one node, are associated into a single transaction. A master node, such as the node that owns the set of resources corresponding to the modifications in the transaction requests permission from a locker node to replicate the transaction. When permission to replicate the transaction is received from the locker node, the master node replicates the transaction by requesting each node in the cluster, one node at a time, to commit the transaction. Any node that does not commit the transaction is removed from the cluster, ensuring consistency of the cluster. Failure conditions of any node or nodes are also handled in a manner that ensures consistency.

Abstract: A high color resolution image is accurately approximated with a low resolution image through a unique combination of ordered dithering and error diffusion. The true color of each pixel is modified with error from previously rendered pixels and then dithered to an intermediate color of 15 bits. The intermediate color is then mapped to the nearest displayable color in a displayable color palette using a precomputed look-up table. Any error between a displayed color of a pixel and its true color is calculated and spread among neighboring pixels not yet rendered.

Abstract: A high color resolution image is accurately approximated with a low resolution image through ordered dithering to colors of a displayable color palette. The colors of the displayable color palette are located at points of a grid aligned with three orthogonal axes in a three dimensional color model, including a luminance axis between black and white. The grid points are defined by the intersections of three sets of parallel planes, each set being perpendicular to one of the three axes. The set of planes perpendicular to the luminance axis are spaced nonuniformly, preferably according to a cubic model. The ordered dithering maps the true color of a pixel in the image to the color in the displayable palette at one of eight adjacent grid points. When ordered dithering of a pixel's true color would map the true color to a grid point outside the color gamut, the pixel is instead mapped to the nearest color on the color gamut's border to the grid point.

Abstract: A custom palette comprises colors on a plurality of luminance levels consisting of colors of uniform luminance. The spacing in luminance between levels varies in relation to the luminance, the spacing between levels being closer at low luminance and increasing at greater luminance. The palette preferably includes a gray color from each luminance level, highly saturated colors at the vertices of every alternate level, and a selection of lower saturation colors encircling the gray color on each level. The selection of lower saturation colors preferably includes a higher concentration of flesh and sky colors.

Abstract: A high color resolution image is rendered using a palette having a lower color resolution. The color of each pixel in the image is mapped to the nearest of the palette colors located on or between levels of uniform luminance adjacent to the pixel color. The mapping of the pixel color is further constrained to exclude palette colors for which double the error to the pixel color is outside the color gamut. The mapping is performed efficiently by a look-up table, the size of which is reduced by first dithering the pixel color to a color in an intermediate palette and then indexing the table using the intermediate palette color to find the reduced palette color.