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Usually, when we say scale-space , we do not mean a pyramid, we mean a varying blur. in .NET Encoding 3 of 9 barcode in .NET Usually, when we say scale-space , we do not mean a pyramid, we mean a varying blur.




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Usually, when we say scale-space , we do not mean a pyramid, we mean a varying blur. use .net vs 2010 39 barcode integration torender barcode 3 of 9 on .net Platform SDK Fig. 5.9.

A pyra .net vs 2010 Code 39 Full ASCII mid is a data structure which is a series of images, in which each pixel is the average of four pixels at the next lower level..

Fig. 5.10.

A Gau ssian pyramid, constructed by blurring each level with a Gaussian and then 2 : 1 subsampling.. Linear operators and kernels Fig. 5.11. This Laplacian pyramid is actually computed by a difference of Gaussians. Quad trees A quad tree [5.2 1] is a data structure in which images are recursively broken into four blocks, corresponding to nodes in a tree. The four blocks are designated NW (north west), NE, SW, and SE.

The correspondence between the nodes in the tree and the image are best illustrated by an example (see Fig. 5.12).

In encoding binary images, it is straightforward to come up with a scheme for generating the quad tree for an image: If the quadrant is homogeneous (either solid black or solid white), then make it a leaf, otherwise divide it into four quadrants and add another layer to the tree. Repeat recursively until the blocks either reach pixel size or are homogeneous. It is easy to make a quad tree representation into a pyramid.

It is only necessary to keep, at each node, the average of the values of its children. Then, all the information in a pyramid is stored in the quad tree. If an image has large homogeneous regions, a quad tree would seem to be an ef cient way to store and transmit an image.

However, experiments with a variety of images, even images which were the difference between two frames in a video. 310 312 33 32 2. 30 310. 32 311 312 313. Fig. 5.12.

An im age is divided into four blocks. Each inhomogeneous block is further divided. This partitioning may be represented by a tree.

. 5.9 Scale space sequence, have s hown that this is not true. Since the difference image is only nonzero where things are moving, it seems obvious that this, mostly zero, image would be ef ciently stored in a quad tree. Not so.

Even in that case, the overhead of managing the tree overwhelms the storage gains. So, surprisingly, the quad tree is not an ef cient image compression technique. When used as a means for representing a pyramid, it does, however, have advantages as a way of representing scale space.

Another disadvantage of using quad trees is that a slight movement of an object can result in radically different tree representations, that is, the tree representation is not rotation or translation invariant. In fact, it is not even robust. Here, robust means a small translation of an object results in a correspondingly small change in the representation.

One can get around this problem, to some extent, by not representing the entire image, but instead, representing each object subimage with a quad tree. The generalization of the quad tree to three dimensions is called an octree. The same principles apply.

. A good way to re .NET barcode code39 member large and small scale is that at large scale, only large objects may be distinguished..

Gaussian scale structures We know how to b .NET Code-39 lur an image. Here is a gedankenexperiment for you: Take an image, blur it with a Gaussian kernel of standard deviation 1.

You get a new image. Call that image 1. Now, blur the original image with a Gaussian kernel of standard deviation 2.

Call that image 2. Continue until you have a set of images which you can think of as stacked, and the top image is almost blurred away. We say the top image is a representation of the image at large scale.

This stack of images is referred to as a scale space representation. Clearly, we are not required to use integer values of the standard deviation, so we can create scale space representations with as much resolution in scale as desired. The essential premise of scale space representations is that certain features can be tracked over scale, and how those features vary with scale tells something about the image.

A scale space has been formally de ned [5.25, 5.26] as having the following properties.

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