Concept of Pixel
The full form of the pixel is "Picture Element." It is also known as "PEL." Pixel is the smallest element of an image on a computer display, whether they are LCD or CRT monitors. A screen is made up of a matrix of thousands or millions of pixels. A pixel is represented with a dot or a square on a computer screen.
The good thing is that a pixel cannot be seen as they are very small which result in a smooth and clear image rather than "pixelated." Each pixel has a value, or we can say a unique logical address. It can have only one color at a time. Colour of a pixel is determined by the number of bits which is used to represent it. A resolution of a computer screen depends upon graphics card and display monitor, the quantity, size and color combination of pixels.
As we know that an image is build up of thousands and millions of pixels. In the above images, if we zoom in the image, we will be able to see some of the pixels.
Relationship with CCD array
When an image has zoomed in, the surface of CCD will look like filled dots.These dots are light receptor called photodiode.
CCD sizes are described using Terms like 2 million pixels (megapixel) and 4 million pixels (megapixel). The more the count of pixel, more detailed image is generated. To get a clear and image smooth, CCD and image size is increased.
Calculation of the total number of pixels
Below is the formula to calculate the total number of pixel in an image.
For example: let rows=300 & columns=200
The value of the minimum gray level is 0. The gray level depends on the depth of the image.
For example: In an 8-bit image, gray level is 255. For a binary image, a pixel can only take value 0 or 255. In color image, it can choose values between 0 and 255.
The formula for calculating gray level in a color image is as shown below:
As we know that each pixel has a unique value. 0 is a unique value that means the absence of light. It means that 0 is used to denote dark.
We have a matrix of 3X3 of an image, and each pixel is of value as shown below:
It means the image formed is of 9 pixels which are black.
The image would be something as below: