Science Fair Project Encyclopedia
Digital image
A digital image is a representation of a two-dimensional image as a finite set of digital values, called picture elements or pixels.
Typically, the pixels are stored in computer memory as a raster image or raster map, a two-dimensional array of small integers. These values are often transmitted or stored in a compressed form.
Digital images can be created by a variety of input devices and techniques, such as digital cameras, scanners, coordinate-measuring machines , seismographic profiling , airborne radar , and more. They can also be synthetized from arbitrary non-image data, such as mathematical functions or three-dimensional geometric models; the latter being a major sub-area of computer graphics. The field of digital image processing is the study of algorithms for their transformation.
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Image types
Each pixel of an image is typically associated to a specific 'position' in some 2D region, and has a value consisting of one or more quantities (samples) related to that position. Digital images can be classified according to the number and nature of those samples:
- binary (bilevel)
- grayscale
- color
- false-color
- multi-spectral
- thematic
The term digital image is also applied to data associated to points scattered over a three-dimensional region, such as produced by tomographic equipment. In that case, each datum is called a voxel.
Image viewing
The user can utilize different program to see the image. The GIF, JPG and PNG images can be seen simply using a web browser because they are the standard internet image formats. The SVG format is more and more used in the web and is a standard W3C format.
The more advanced programs offer a slideshow utility, to see the images in a certain forlder one after the other automatically.
Image calibration
Proper use of a digital image usually requires knowledge of the relationship between it and the underlying phenomenon, which implies geometric and photometric (or sensor ) calibration. One must also keep in mind the unavoidable errors that arise from the finite spatial resolution of the pixel array and the need to quantize each sample to a finite set of possible values.
See Also
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