Point Operation

• Point operations perform a mapping of the pixel values without changing the size, geometry, or local structure of the image
• The function $f(.)$ is independent of the coordinates, Such operation is called “homogeneous”

• A nonhomogeneous point operation $g()$ would also take into account the current image coordinate $(u,v)$

Adjustment

• Changing contrast and brightness

• Limiting Results by Clamping

• Inverting Images

Thresholding

Posterization

• A point operation that reduces the number of intensity or color levels in an image, mapping continuous tones into a few discrete bands.
• It produces a flat, layered “poster-like” look by replacing smooth gradients with abrupt transitions between limited tone regions.

Automatic contrast adjustment

• Auto-contrast: a point operation that modifies the pixels such that the available range of values is fully covered.