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CSE 473: Digital Image Processing CSE 473: Digital Image Processing and Pattern Recognitionand Pattern Recognition
Spring 2015Spring 2015
Course Teacher:Course Teacher:Md. Tarek HabibMd. Tarek Habib
Assistant ProfessorAssistant ProfessorDepartment of Computer Science and EngineeringDepartment of Computer Science and Engineering
Green University of BangladeshGreen University of Bangladesh
Topic – 2: Topic – 2: Image FundamentalsImage Fundamentals
BasicsBasics
Classification of ImagesClassification of Images
Image File FormatsImage File Formats
Topic ContentsTopic Contents
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BasicsBasicsAn image is an artifact that has a similar appearance
to some subject—usually a physical object or a person.
A digital image is a representation of a two-dimensional image as a finite set of digital values (0s and 1s). These digital values are called picture elements or pixels.
Pixels are the smallest individual element in an image, holding quantized values that represent the brightness of a given color at any specific point.
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BasicsBasics A digital image contains a fixed number of rows and
columns of pixels. Typically, the pixels are stored in computer memory
as a raster image or raster map, a two-dimensional array of small integers.
Vector images are resulted from mathematical geometry (vector). In mathematical terms, a vector consists of point that has both direction and length.
Raster image: Vector image:
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Classification of ImagesClassification of Images
Digital images can be classified in the following way:
Binary
Gray-scale
Color
False-color
Etc...
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Classification of ImagesClassification of ImagesColor depth, also known as bit depth, is either the
number of bits used to indicate the color of a single pixel in a bitmapped image or video frame buffer.
Color depth is the aspect of color representation, which expresses how finely levels of color can be expressed.
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Classification of Images: BinaryClassification of Images: Binary
The simplest type of image is black and white. It is a binary image since each pixel is either 0 or 1.
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Classification of Images:Classification of Images:GrayscaleGrayscale
The next, more complex type of image is gray scale, where each pixel takes on a value between zero and the number of gray scales or gray levels.
These images appear like common black and white photographs - they are black, white, and shades of gray.
Most gray scale images today have 256 shades of gray.
People can distinguish about 40 shades of gray, so a 256-shade image “looks like a photograph.”
This course concentrates on gray scale images.
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Classification of Images: ColorClassification of Images: Color
The most complex type of image dealt in this course is color.
Color images are similar to gray scale except that there are three bands, or channels, corresponding to the colors red, green, and blue.
Thus, each pixel has three values associated with it.
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Classification of Images:Classification of Images:False-ColorFalse-Color
A false-color image is an image that depicts an
object in colors that differ from those a
photograph (a true-color image) would show.
A false-color image sacrifices natural color rendition
(in contrast to a true-color image) in order to ease the
detection of features that are not readily discernible
otherwise – for example the use of near infrared for
the detection of vegetation in satellite images.
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Classification of Images:Classification of Images:False-ColorFalse-Color
A false-color image of the northern regions
of the moon in December 1992
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Classification of Images:Classification of Images:False-ColorFalse-Color
A true-color image showing the area in
actual colors, e.g., the vegetation
appears in green.
The same area as a false-color
image showing vegetation in a red
tone
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Image File FormatsImage File Formats
Image file formats are standardized means of organizing and storing digital images.
Some image file formats JPEG (Joint Photographic Experts Group) GIF (Graphics Interchange Format) TIFF (Tagged Image File Format) PNG (Portable Network Graphics)
