Abstract: A system for compressing an image. The system determines a set of commonly occurring color values in the image and associates a designator with each commonly occurring color value. For each pixel in the image, the system identifies a color value for the pixel. If the pixel has a commonly occurring color value, the system substitutes the associated designator for the commonly occurring color value. Otherwise, if the pixel does not have a commonly occurring color value, the system adds the color value to a rare color list, and substitutes a special designator for the color value to indicate that the color value for the pixel is contained in the rare color list.

Abstract: Caching fonts on a display computer may be performed in order to reduce network bandwidth utilization and/or to improve CPU usage. Text commands may be recorded when they are executed to create a portion of a graphics image. These text commands may be used to update a data structure with information, and this data structure may be used to more efficiently transmit the text portions of the graphics image. A caching mechanism may be used wherein the font utilized by the text command is stored in the cache if a compatible font does not already exist in the cache. Once the font has been cached, subsequent text commands utilizing the font may be executed with a dramatic reduction in network bandwidth.

Abstract: A mechanism is provided that identifies certain classes of images that are likely to be re-used, and utilizes this information to manage a cache better. This may include flushing certain classes of images that are less likely to be re-used before flushing the classes that are more likely to be reused. In addition, or alternatively, other factors regarding the image may be utilized to determine whether or not caching of the image should occur.

Abstract: One embodiment of the present invention provides a system for compressing an image. During operation, the system determines a set of commonly occurring color values in the image and associates a designator with each commonly occurring color value. Next, for each pixel in the image, the system identifies a color value for the pixel. If the pixel has a commonly occurring color value, the system substitutes the associated designator for the commonly occurring color value. Otherwise, if the pixel does not have a commonly occurring color value, the system adds the color value to a rare color list, and substitutes a special designator for the color value to indicate that the color value for the pixel is contained in the rare color list.

Abstract: Repeating image content in a graphics image may be detected by identifying certain commands, known generally as “tile commands”. If a tile command is detected, the fact that a portion of an image was created with a tile command may be stored along with the portion of the image. This allows for well-informed decision making when transmission of the image is to be performed. For example, this allows for the transmission of a single tile, and subsequent transmission of local copy commands to repeat the single tile. This can be very useful in speeding transmission of background images or other repeating images.

Abstract: A solution is provided to reshape irregularly-shaped computer graphics images in order to reduce the number of rectangles generated for transmission. It may be used any time it is useful to compress a set of digital image data from an irregularly-shaped region of pixels. A post-shaping process may be utilized wherein rectangles in a destination window are examined and any touching (or possibly nearby) rectangles are merged into a single rectangle. Alternatively, a pre-shaping process may be utilized wherein images drawn with a single command are merged into a single rectangle. Each of these processes has advantages and disadvantages which may make one or the other preferable, depending upon the circumstances. Additionally, both processes may be used together if desired.

Abstract: The storing of not only image content but information regarding what commands were used to create the image allows for well-informed decision making. The drawing commands are recorded and may be stored in a data structure. This data structure may then be accessed at the time of compression, and the selection of which compression technique to use may be based on the drawing commands. Pixmaps are data structures holding pixel values corresponding to an image in memory. The data structure utilized here may be a linked list identifying fill regions. This permits the well-informed decision making to be accomplished even when pixmaps are copied to realized (on-screen) windows or other pixmaps.

Abstract: A method and system for buffering image updates for a remote application. An image update produced by a remote application is accessed for transmission from a host computer system to a display computer system. The image update is buffered to generate an image data set of the image update, wherein the image data set is configured for processing by an image compression routine. The buffering is performed by the host computer system. The image data set is processed using the image compression routine to produce a compressed image data set. The compressed image data set is subsequently transmitted to the display computer system via a network connection.

Abstract: The storing of not only image content but information regarding what commands were used to create the image allows for well-informed decision making. The drawing commands are recorded and may be stored in a data structure. This data structure may then be accessed at the time of compression, and the selection of which compression technique to use may be based on the drawing commands. Thus, certain codecs may be applied to certain portions of the image, resulting in a more efficiently compressed image. Pixmaps are data structures holding pixel values corresponding to an image in memory. The data structure utilized here may be a separate RGB pixmap region associated with a pixmap holding image data. This permits the well-informed decision making to be accomplished even when pixmaps are copied to realized (onscreen) windows or other pixmaps.

Abstract: A method for significantly decreasing the number of times prior art coding schemes, such as variable length coding, are implemented in the course of encoding/decoding a given data block includes cataloging the occurrences, or locations, of a designated frequently occurring value in the data block and then excluding the frequently occurring value from the prior art coding scheme.

Abstract: A method for significantly decreasing the number of times prior art coding schemes, such as variable length coding, are implemented in the course of encoding/decoding a given data block includes cataloging the occurrences, or locations, of a designated frequently occurring value in the data block and then excluding the frequently occurring value from the prior art coding scheme.