• In zero memory operations, output image pixel value is obtained directly processing input image image pixel values. Output pixel value at (x, y)position depends on single input pixel at (x, y).

• For every input image pixel value, Transformation function gives corresponding output image pixel value, no memory location is required to store intermediate results.

  The various Zero Memory Point operations are:

  • Contrast Stretching Transformation
  • lipping and Thresholding
  • Digital Negative Transformation
  • Logarithmic Transformation
  • Power Law Transformation
  • Intensity Level Slicing Transformation and
  • Bit Level Slicing Transformation.

  Let r denotes input image pixel valueand S denotes output image pixel value

  Then S=T(r); where T is any Zero memory point operation Transformation function.

  Point processing Techniques:

1.Contrast Stretching Transform:

Contrast Stretching Tx function increases the dynamic range of modified image.

• It is defined as S=T(r)

  Where T is Contrast Stretching Tx function such that,

$$s=\begin{bmatrix}ar & & 0 \leq r \leq a \\ S1+ \beta (r-a) & & a \leq r\leq b \\ S2+ \gamma(r-b) & & b \lt r \leq L-1 \end{bmatrix}$$

2.Clipping and Thresholding Transformation:

• Clipping is extension of Contrast Stretching Tx function.

• Consider of Contrast Stretching Tx function:

  Case 1: When α=0 and γ=0

$$s=\begin{bmatrix}0 & & 0 \leq r \leq a \\ S1+ \beta (r-a) & & a \leq r\leq b \\ S2 & & b \lt r \leq L-1 \end{bmatrix}$$

Case 2: When α=0,γ=0 and S1=0

$$s=\begin{bmatrix}0 & & 0 \leq r \leq a \\ \beta (r-a) & & a \leq r\leq b \\ S2 & & b \lt r \leq L-1 \end{bmatrix}$$

• Thresholdng Transformation function is defined as S=T(r)

  Such that,

  S=

3.Digital Negative Transformation:

• Digital Negative reverses the gray scale of input image.

• It is defined as S=T(r)

  Where T is the Digital Negative Tx Function

Such that, S=(L-1)-r

• It is used to obtain Negative print of photograph and to display X-ray images.