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Scan Conversion in Computer Graphics

“When we represent regular objects in the form of discrete pixels, it is called Scan Conversion.” Every graphics system must transform the primitives into a collection of pixels. The scan conversion is also called “Rasterization.” Each pixel in the graphical system has two states either on or off.

“The Scan Converting rate is a technique that is used in video processing. In this technique, we can change the horizontal and vertical frequency for many different purposes.” We use a scan converter to perform scan conversions. We can define a line by its starting and ending points. On the other hand, we can define a circle by its radius, circle equation, and center point.

Methods of Scan Conversion

We can perform scan conversion by using two methods.

  • Analog Method
  • Digital Method
  • Analog Method: It is the best method for analog videos. A large number of delay cells perform the analog method. The Analog approach is also known as “Non-retentive, memory-less, or real-time method.”
  • Digital Method: Digital method is also known as a “retentive or buffered method.” In the digital method, there is a concept of n1and n2 speed. We can save (Store) the picture in line or frame buffer with n1 speed. The image can be read with n2 speed.    

Some Examples of scan converted objects

 We can apply the conversion to the following objects.

  • Line
  • Point
  • Polygon
  • Rectangle
  • Filled Region
  • Arc
  • Character
  • Sector
  • Ellipse

Pixel

“We can define a pixel as a rectangular dot centered at an integral position on an integral grid.” It is a real point that is addressable. The pixel is also called “picture element (Pel).”

A pixel includes its own:

  • Intensity – The intensity of a pixel defines the brightness of the image that appears on the screen.
  • Name or Address- The name or address of a pixel defines the position of the pixel.

We can define the size of any image with a total number of horizontal pixels and the total number of vertical pixels.

For Example- (512 x 512, 640 x 480, or 1024 x 768).

We can measure the ratio of an image’s width to its height in unit length or number of pixels, is known as the aspect ratio of the image.

For example- A Pixel having a coordinate (8,10).

Scan Conversion

Advantages of Scan Conversion

  1. The scan conversion technique is used for various purposes, such as videoProjectors,TV, HDTV, Video capture card, LCD monitor, etc.
  2. The Scan Conversion technique has wide applications.
  3. We can efficiently perform scan conversion using high speed integrated circuits.

Disadvantages of Scan Conversion

  1. We can only apply scan conversion with LSI and VLSI integrated circuit.
  2. Int the digital scan conversion, the analog video signal has changed into digital data.

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