The preprocessing is the common name for operations with images at a lowest level of abstraction both input and output of the intensity images. Preprocessing is a method mainly given the enhanced output of the input image. The development of the image is done by preprocessing method without the distortions. In this step is performed to minimize noise and resizing the original image. Also, the image gets smoothed after this process. Preprocessing which includes many steps for an example noise removal, converting into a gray scale image, normalization, localization and etc. Image preprocessing methods uses to considerably redundancy in images reduces the noise and improve (or) increase number of the pixels of the dataset.
In this paper the preprocessing includes the converting into grayscale image from the raw image and noise removal of the input image.
Converting into gray scale image
In real time the iris images consist of primary colors it is very difficult to get the result and it has complex computational process as well. Because primary colors have its own property and if we concentrate on that, the process goes too big and difficult and it takes much time. To overcome, this issue the gray scale images has been uses in the preprocessing method. Fig.1 shows converting an real image into a gray image, it gives the range of shades of gray without apparent color. This method is very much important in the preprocessing because the computational step of the gray scale image is simple and easy to use for further process in image processing. After the conversion the image consists only two colors (Black and white). Where it may represent in the form of binary (0 and 1) and decimal (0 to 255) values.
The gray scale image is depending on the amount of primary colors involving in the input image. And output of gray image is equal to the input of the primary image. so, there is no more information is loss in this method. Only the image is converted into a gray scale image.
The black color is represented in the gray scale is the darkest possible shade, which is the total absence of transmitted or reflected light and the white color is defined in form of the light possible shade, which is total presence of transmitted or reflected light.
Comparing with primary colors the black and white is represented by R=G=B = 0 or R=G=B =00000000 and R=G=B =1 or R=G=B =11111111 for a 8bit gray scale image. This method is also known as black and white image.
The three main parameters are defined in the gray scale image that is saturation, hue, brightness. In each pixel the saturation and hue are equal to 0 but the brightness is only the parameter can vary from min of 0(black) to max of 1(white).