- 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.