Browse Prior Art Database

Image Rotation Method

IP.com Disclosure Number: IPCOM000038432D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 75K

Publishing Venue

IBM

Related People

Inoue, K: AUTHOR [+2]

Abstract

This article describes an image rotation method wherein image data is divided and compressed before rotation to reduce the processing time. In processing image data in a personal computer (PC), the entire image data can not be maintained in the working memory of the PC. Thus, the image data is divided into plural blocks or sections and stored in an auxiliary storage from which the sections are selectively fetched onto the working memory for subsequent processing, such as rotation. Fig. 1 shows an example to rotate a source image clockwise by 90 degrees. The source image comprising a matrix of Sx x Sy dots is divided into plural sections identified by S(J,I), where J=1...n, I=1...m, and n=3, m=2 in this example, as shown in Fig. 1(A). These sections are successively processed according to the flowchart shown in Fig. 2.

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Image Rotation Method

This article describes an image rotation method wherein image data is divided and compressed before rotation to reduce the processing time. In processing image data in a personal computer (PC), the entire image data can not be maintained in the working memory of the PC. Thus, the image data is divided into plural blocks or sections and stored in an auxiliary storage from which the sections are selectively fetched onto the working memory for subsequent processing, such as rotation. Fig. 1 shows an example to rotate a source image clockwise by 90 degrees. The source image comprising a matrix of Sx x Sy dots is divided into plural sections identified by S(J,I), where J=1...n, I=1...m, and n=3, m=2 in this example, as shown in Fig. 1(A). These sections are successively processed according to the flowchart shown in Fig. 2. That is, section S(J,I) is rotated and compressed using an appropriate compression technique unless it contains all white dots. The compressed data 10, 11, 12 and 13 are stored in a memory area, as shown in Fig. 1(C). For the section containing all white dots, neither rotation nor compression is conducted. During the above operation, the following table is formed. The table row T(J,I) includes information related to section S(J,I), i.e., FLAG indicating whether the dots are all white (W) or not (B), POINTER indicating an address of a location storing the compressed data, and LENGTH indicating the length of the compressed data....