Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
1998-12-03
2001-10-30
Mancuso, Joseph (Department: 2621)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
C345S182000
Reexamination Certificate
active
06310986
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to a method and apparatus for assisting in the rotation of digital image data. In particular, the invention relates to a method of assisting in the placement of rotated image blocks in an image buffer.
BACKGROUND OF THE INVENTION
Document imaging systems (e.g., copiers and fax machines) often represent an image as digital data for use in the reproduction of the original image. Some document imaging systems include an image processing chip which provides an image block rotation assist function for rotation angles which are integer multiples of 90°. The output of this rotation assist function is a version of the input image which has been divided into individually rotated image blocks. Logic is implemented (in software or hardware) independent of the chip to place the rotated image blocks in a frame buffer to create a properly rotated image therein. The logic can be computationally intensive. The problem is further complicated if the frame buffer is larger than the output image (e.g., when placing multiple rotated images onto a single page).
Since the output bandwidth of these image processing chips is usually high, output data is typically handled by a hardware data moving device (e.g., a DMA controller). When the output of the image processing chip includes rotated image blocks, the required block placement creates an additional burden on the data moving device. A processor can used to read each output unit (e.g., byte, word) and properly place it in the frame buffer, however, use of the processor can substantially limit the rate at which image blocks are placed in the frame buffer. Hardware can be designed to determine and place the image blocks in memory, but such hardware is usually required to perform multiplication operations to generate the proper frame buffer address. Multiplication operations require a substantial number of digital logic components in the hardware and limit the rate at which image blocks are transferred into memory.
SUMMARY OF THE INVENTION
The present invention relates to a method and apparatus for proper placement of rotated image blocks in an image memory module which can be implemented in simple data moving hardware. A processor provides a set of information to a hardware data mover before an image is processed, and the data mover performs a simple set of operations quickly and without need for multiplication operations or further processor intervention. The processor performs a set of predetermined calculations to generate the set of information for the data mover. A set of simple operations which are independent of the rotation increment (i.e., 0°, 90°, 180° or 270°) are then performed by the data mover to generate single or multiple images within the image memory module. These operations place the rotated image blocks in the proper location in the memory module. Thus, a single process of reduced complexity can be implemented in hardware which requires no processor intervention.
In one aspect, the invention features a method for assisting in the rotation of a digital image. A set of precalculated values generated by a value processor is received. Rotated image blocks comprised of sub-blocks from an image processor are also received. A destination address for each sub-block is determined according to the precalculated values and each sub-block is stored at its destination address in an image memory module. The generation of the precalculated values can be based on a predetermined rotation angle, an image block size, horizontal and vertical dimensions of the digital image, and an image memory module dimension. In one embodiment, the precalculated values are generated prior to determining each destination address. In another embodiment, each destination address is determined using only addition and subtraction operations. In yet another embodiment, a digital image is received and the rotated image blocks are generated from the digital image.
In another aspect, the invention features an apparatus for assisting in the rotation of a digital image. The apparatus includes a rotation assist module electrically coupled to a memory module. The rotation assist module includes a value input for receiving precalculated values and a rotated block input for receiving a plurality of rotated image blocks comprising a plurality of sub-blocks. The memory module stores each sub-block at a corresponding destination address generated by the rotation assist module. In one embodiment, a processor for generation of the precalculated values is electrically coupled to the rotation assist module. In another embodiment, the apparatus includes an input module for receiving the digital image and an image processor for generating and rotating the plurality of image blocks.
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Busa Mark
Robey Joshua
Kassa Yosef
Mancuso Joseph
Oak Technology, Inc.
Testa Hurwitz & Thibeault LLP
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