ABSTRACT
This chapter reviews a number of general techniques that have been developed to facilitate computer-aided flow visualization. Computer-aided flow visualization is a rather broad category that refers to the use of digital computer processing in combination with various display devices to enhance ability to visually understand fluid flow behavior. Clearly, in order to perform any type of computer image enhancement or manipulation, the quality of the original image should be as good as possible. However, in many cases, the image-acquisition process is impaired by inadequate lighting, the wrong shutter speed or depth of focal field, lens irregularities, or poor film or image-detector resolution. Filtering is a general term implying a spatial or frequency transformation of the image intensities in order to enhance or deemphasize certain features of the image. This can be done to sharpen the intensity discontinuities between image regions or, conversely, to soften the discontinuities. Thresholding is probably the easiest of all image-enhancement processes to apply.
