US5111192A
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US
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Method to rotate a bitmap image 90 degrees
Assignee: Xerox Corp
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Filing: 1989-12-20
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Granted: 1992-05-05
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Expires: 2009-12-20
Abstract
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.
Inventors
- 👤 Vinod K. Kadakia
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 15:30
CPC Classifications
G; G06; G06T; G06T3/00; G06T3/60; G06T3/602
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
156 words
The method of rotating an original n column by n row image, each column comprising a word, comprising the steps of: A. storing said image in a buffer, said storing step comprising the steps of: a. first circular shifting each original word by a number of pixels equal to the column number, and b. storing each shifted word in the location of said buffer equal to the column number, and B. outputting an n column by n pixel image from said buffer, where the column number j and the pixel number i of the buffer varies from 0 to n-1, said outputting step for each word output comprising the steps of: a. assembling the jth output n pixel word from n pixels of the buffer, where pixel number i of the assembled word comes from pixel number i of word number (i+j+1)mod n of the buffer, and b. second circular shifting the resultant word j+1 pixels.
Claim 2
Independent Claim
156 words
The method of rotating an original n column by n row image, each column comprising a word, comprising the steps of: A. storing said image in a buffer, said storing step comprising the steps of: a. first circular shifting each original word by a number of pixels equal to the column number, and b. storing each shifted word in the location of said buffer equal to the column number, and B. outputting an n column by n pixel image from said buffer, where the column number j and the pixel number i of the buffer varies from 0 to n-1, said outputting step for each word output comprising the steps of: a. assembling the jth output n pixel word from n pixels of the buffer, where pixel number i of the assembled word comes from pixel number i of word number (i+j+1)mod n of the buffer, and b. second circular shifting the resultant word j+1 pixels.
Claim 3
Dependent Claim
33 words
The method of reorienting an image comprising the steps of: using the method of claim 1 to rotate an image, and reversing the order of the scan lines to produce a mirror image.
Claim 4
Dependent Claim
36 words
The process of reorienting an image comprising the steps of: using the method of claim 1 to rotate an image, and reversing the order of the pixels in each scan line to produce a mirror image.
Claim 5
Independent Claim
147 words
A method of rotating an original image having r rows, c columns, w pixels per word, v words per column and h words per row, into a rotated image using an index i to count the words, where i varies from 0 to h-1 and using an index j to refer to the columns where j varies from 0 to r-1, comprising the steps of first circular shifting each word in the original image by a number of shifts equal to its column number, storing each word in a buffer memory so that the word number in the buffer equals the word number of the original image, reading out one word at a time from the buffer wherein each pixel p of this output word comes from pixel p of buffer word address wvi+v((p+j+1)mod w)+ (wv-j-1)/w , and second circular shifting this assembled word (j+1)mod w pixels.
Claim 6
Independent Claim
147 words
A method of rotating an original image having r rows, c columns, w pixels per word, v words per column and h words per row, into a rotated image using an index i to count the words, where i varies from 0 to h-1 and using an index j to refer to the columns where j varies from 0 to r-1, comprising the steps of first circular shifting each word in the original image by a number of shifts equal to its column number, storing each word in a buffer memory so that the word number in the buffer equals the word number of the original image, reading out one word at a time from the buffer wherein each pixel p of this output word comes from pixel p of buffer word address wvi+v((p+j+1)mod w)+ (wv-j-1)/w , and second circular shifting this assembled word (j+1)mod w pixels.
Claim 7
Dependent Claim
33 words
The method of reorienting an image comprising the steps of using the method of claim 3 to rotate an image, and reversing the order of the scan lines to produce a mirror image.
Claim 8
Dependent Claim
36 words
The process of reorienting an image comprising the steps of: using the method of claim 3 to rotate an image, and reversing the order of the pixels in each scan line to produce a mirror image.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-05-05 | 1995-11-04 | 1996-05-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-05-05 | 1999-11-04 | 2000-05-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-05-05 | 2003-11-04 | 2004-05-05 | $7700.00 | Window Closed / Lapsed |