| Specifications | The method of wavelet thresholding for removing noise, or denoising, has been researched extensively \ due to its effectiveness and simplicity Amjed Al-Fahoum |
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| Specifications | The method of wavelet thresholding for removing noise, or denoising, has been researched extensively \ due to its effectiveness and simplicity Amjed Al-Fahoum |
| Business section |
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| Specifications | The method of wavelet thresholding for removing noise, or denoising, has been researched extensively \ due to its effectiveness and simplicity Amjed Al-Fahoum |
| Outline | 1. Introduction 2. 1-D Resampling 3. 2-D Image Resizing 4. 2-D Image Rotation FPGA Implementation Conclusion References |
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| Content | Real Time Image Rotation and Resizing, Algorithms and Implementations Robert D. Turney and Chris H. Dick CORE SOLUTIONS GROUP, XILINX, INC. 2100 LOGIC DRIVE SAN JOSE, CA 95124-3450 ABSTRACT Recent growth in the area of digital communications has been fueled by new and exciting communications algorithms to satisfy the ever increasing bandwidth needs. While the majority of the bandwidth requirements are driven by multi-channel voice or data needs, video and imaging communications is becoming both realizable and practical. Additional progress in the area of video and imaging compression has reduced the bandwidth requirements for video communications thus enabling video conferencing, video broadcast, and video wireless applications. With the continued growth in the video communication industry different size and orientation of image data sets is a noteworthy problem to address. In this work we will explore implementation of image rotation and resizing for both low and high quality imaging systems. Implementations are proposed for real time processing using field programmable gate arrays (FPGAs). 1. Introduction When addressing the problem of image resizing one needs to satisfy the two dimensional sampling theorem [1]. Aliasing and “imaging” found in one dimensional signal processing are extended to two dimensional processing with spatial distribution rather than time dependency. In a majority of one dimensional multi-rate systems integer decimation or interpolation resampling are often the case. Image resizing typically involves fractional resampling and can lead to prohibitively large implementations resulting in comprimises in range and resolution. Additional requirements due the the human visual system (HVS), such as constant aspect ratio, edge sensitivity, and noise uniformity add constraints to the image resize algorithm. In addition, frequently one must also deal with interlaced video data as an input to the imaging system. In this work we will discuss traditional bilinear and bicubic interpolation methods from an algorithm and real time implementation perspective. The problem of image rotation is becoming more prevalent due to the emergence of flat panel and CCD acquisition devices. While commercial applications for rotation may be of a limited nature, medical, military and industrial uses for image rotation abound. Similar to image resizing, interpolation algorithms must be utilized to achieve image quality acceptable for the particular application. Since, in general, image rotation involves a rectangular shaped image, image cropping and padding needs to be incorporated into the algorithm. One of the more challenging problems in image resizing and rotation is dealing with edge preservation in the presence of noise with a real time implementation. In this work we deal with the computational aspects of implementing image resize and rotation by efficient co-design of algorithmic aspects and implementation aspects so that memory bandwidth and frame latency considerations are included. 2. 1-D Resampling Resampling by decimation of digital data requires one to pay attention to the Nyquist rate to eliminate aliasing. For example if a 512 pixel line is decimated by 4 to produce 128 pixels a quarter-band filter would be employed to eliminate the high frequecy from folding into the low frequecy terms. This structure is usually implemented as a polyphase decimator |
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