Image and Video Processing Libraries in Ptolemy II by ... - CiteSeerX

Chapter 2
Image Processing Platform
2.1 Images in JAI
The RenderedOp is the data structure from JAI that is used in this platform.
Images inside this data structure are not rendered until they need to be (for
instance if the width or height of the image is required, or if the images themselves
need to be rendered to display).
Images are a collection of points called pixels, and typically are thought of
as having a band for each salient feature. For instance in an RGB (Red, Green,
Blue) image, all of the red pixels form a band, all of the green pixels form a
band, and all of the blue ones form a band.
However, bands do not necessarily contain intensity data. When a Discrete
Fourier Transform (see section 3.5.1 on page 39) is performed on an image,
the image will be represented as frequency data. This data, mathematically, is
typically complex, so a color in the spatial domain will be represented as two
bands in the frequency domain (one for each part of a complex number).
2.1.1 Origin
The origin of an image is typically the top left corner. Almost all the actors
preserve the location of the origin. The origin can be moved however, by using
the JAITranslate (see section 3.2.8 on page 33) actor. This does not change how
the image is displayed or saved, but it will effect the output of some actors that
involve two or more images (for instance, when two images are added together,
only the intersection of the two images are used).
2.1.2 Data Types
When stored or loaded, image data is in one of the many non-floating point data
types. However what goes on within a model may change the internal data type
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