Aliasing:
- In computer graphics, the process by which smooth curves and other lines become jagged because the resolution of the graphics device is not high enough to represent a smooth curve.
- Antialiasing techniques can reduce the effect of aliasing.
Antialiasing:
- Aliasing is the visual stair-stepping of edges that occurs in an image when the resolution is too low.
- Anti-alising is the smoothing of jagged edges in digital images by averaging the colors of the pixels at a boundary.
- The letter on the left is aliased. The letter on the right has had anti-aliasing applied to make the edges appear smoother.
- To remove this effect we use antialiasing methods i.e,
1. Super Sampling / Post Filtering
2. Area Sampling / Pre Filtering
2. Area Sampling / Pre Filtering
1. Super Sampling / Post Filtering:
- In this method, we can divide each pixel into a no.of sub pixels and count the no.of sub pixels that overlap the line path. The intensity of each pixel is set to a value proportional to this sub pixel count.
- This process means calculating a virtual image at a higher spatial resolution than the frame store resolution and then averiging down to the final resolution. It is called postfiltering as the filtering is carried out after sampling.
2. Area Sampling / Pre Filtering:
- In this method,each pixel is given an intensity depending on the area of overlap of the pixel and the line. So, due to the blurring effect along the line edges, the effect of antialiasing is not very prominent, although it still exists.
- Pre Filtering thus amounts to sampling the shape of the object very densely within a pixel region. For shapes other than polygons, this can be very computationally intensive.
Real Time Applications of Super Sampling:
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| Used in Magnifying Glass |
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| Used in Spectacles |
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| Used in Google Maps |
Real Time Applications of Area Sampling:
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| Used in Photoshop |
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| Used in Mobile Phones |
- By using this we can get smooth images and text.
- Reduces the visual defects.
- Improves the appearance.
Disadvantages of Antialiasing:
- When you are upsampling (enlarging) images in a graphic program, that you will never actually get more resolution out of a digital enlargement.