Method to rotate a bitmap image 90 degrees
US5111192A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 20, 1989 |
| Grant date | May 5, 1992 |
| Priority date | — |
| Expiry date | Dec 20, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T3/602
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An algorithm for rotating an image 90 degrees starts with an array or r rows and c columns of pixels. Each column of the pixel array is partitioned into words of w pixels each, and the rows, the columns, the words in each column, and the pixels in each word of the pixel array are all numbered starting at zero. Let v= r/w , where r/w is the smallest integer greater than or equal to r/w. Similarly, let h- c/w . The algorithm stores words of the original pixel array into a linear word organized memory as follows: it circular right-shifts each word i of column j by (j)mod w pixel positions and then writes in parallel this modified word into word address vj+i of the memory. The algorithm fetches words of the stored pixel array from this memory rotating this pixel array 90 degrees as follows: it reads a whole word in parallel such that each pixel p of this word comes from pixel p of word address wvi+v((p+j+1)mod w)+ wv-j-1/w) and then circular right-shifts this word by (j+1)mod w pixel positions, thereby delivering word i of column j of a 90 degree rotated version of the original pixel array.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.