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Logical Rotation and Reflection of Graphic Raster Images

IP.com Disclosure Number: IPCOM000045317D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Fedak, JF: AUTHOR [+2]

Abstract

In all points addressable printers and displays, it is often desired to present the graphic information in selective orientation; generally data is received in a given orientation from a graphics source, such as a host computer. A combination of microcode in a microcomputer controlling and sequencing a raster-rotation circuit provides a cost- effective, raster-rotation apparatus. The graphics image is subdivided into N bit by M bit (N and M are integers) subrasters, with the hardware rotating the bit positions within each subraster. The microcode determines the sequence of transmissions of the subrasters for completing the rotation of the entire graphics image. Such rotation can be applied for alphanumeric symbols as well as logos and pictures.

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Logical Rotation and Reflection of Graphic Raster Images

In all points addressable printers and displays, it is often desired to present the graphic information in selective orientation; generally data is received in a given orientation from a graphics source, such as a host computer. A combination of microcode in a microcomputer controlling and sequencing a raster-rotation circuit provides a cost- effective, raster-rotation apparatus. The graphics image is subdivided into N bit by M bit (N and M are integers) subrasters, with the hardware rotating the bit positions within each subraster. The microcode determines the sequence of transmissions of the subrasters for completing the rotation of the entire graphics image. Such rotation can be applied for alphanumeric symbols as well as logos and pictures.

The graphics data is received for a text symbol in raster form.

Consider a raster subdivided into six subrasters, A-F. The received graphics image has a top identified by the subrasters A and B. Microcode controls the data flow to the subraster rotation unit (storage array) for orienting the image in any one of eight orientations. The first orientation, which corresponds to the received orientation, is called up,forward. The sequence of subraster transmissions is A-F, in that order. To reverse (reflect) the image, i.e., face it backwards (up,backward), the subraster transmission sequence is B,A,D,C,F,E. To invert the image but maintain its forward/backward orientation (down, forward), the transmission sequence is E,F,C,D,A,B. To invert the image and reverse its horizontal orientation (down,backward), the transmission sequence is F,E,D,C,B,A. To rotate the image on its side (for example, rotating from a portrait presentation to landscape presentation, (left,up), the transmission sequence is B,D,F,A,C,E. For the landscape orientation with the image facing down (left,down), the transmission sequence is A,C,E,B,D,F. To reverse (reflect) the horizontal image, but maintain its vertical orientation in the landscape presentation (right,up), the transmission seque...