Real-time feature extraction from video stream data for stream ...

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Real-time feature extraction from video stream data for stream ...

6. Feature Extraction

[Rafael C Gonzalez and Woods, 2008], or applying other filters, that sharpen images.

Image Sharpening Whenever edges, line structures or other details in an image are

important, image sharpening filters are used to enhance these structures. These

filters try to detect edges and increase the intensity of the detected edges in the

resulting image. For further information about edge detection please see chapter

6.2.1. The big challenge is to enhance edges without increasing noise at the same

time. Although there are existing approaches (i.g. [Alvarez et al., 1992]), the problem

is still an open field for further research.

IMMI offers miscellaneous filters. All of them are available over the Image Filters package.

Border detection

The detection of borders (also called ”edge detection”) in an image might be a useful

method in order to get abstract information about the image. The border detection

algorithm implemented in IMMI operates on color images. These color images are first

of all transformed into a color-space containing 64 colors. This is done by uniformly

quantizing each of the RGB color channels into four quantiles. Afterwards each pixel,

having all four neighbors (top, bottom, left, and right) the same quantized color, is

classified as an interior pixel. All other pixels are classified as border pixels. The outcome

is a black and white image, where all border pixels are black and all interior pixels are

white. Figure 6.5 shows an example for this. The correspondent operator is called Border

/ Interior Classification (short: BIC) operator.

(a) Original image

(b) Transformed Image

Figure 6.5.: Example for border detection on a color image.

Difference images

As RapidMiner offers no functionality to operate on video data, there is no way to benefit

from any features that can be gained from the MPEG compression. Unfortunately some

of the presented approaches for shot boundary detection base on these features, especially

the difference image of two frames. Therefore I ”emulated” the MPEG compression in

RapidMiner by reproducing the difference image of two frames and extracting features

on these difference images. The corresponding process is shown in figure 6.6.

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