# Chapter 2: Concept of Pixel in Digital Image Process

## Concept of Pixel

#### Pixel

Pixel is the smallest element of an image. Each pixel correspond to any one value. In an 8-bit gray scale image, the value of the pixel between 0 and 255. The value of a pixel at any point correspond to the intensity of the light photons striking at that point. Each pixel store a value proportional to the light intensity at that particular location.

### PEL

• A pixel is also known as PEL. You can have more understanding of the pixel from the pictures given below.
• In the above picture, there may be thousands of pixels, that together make up this image. We will zoom that image to the extent that we are able to see some pixels division. It is shown in the image below.

figure 1

### Relationship with CCD array

• We have seen that how an image is formed in the CCD array. So a pixel can also be defined as
• The smallest division the CCD array is also known as pixel.
• Each division of CCD array contains the value against the intensity of the photon striking to it. This value can also be called as a pixel.

### Calculation of total number of pixels

• We have define an image as a two dimensional signal or matrix. Then in that case the number of PEL would be equal to the number of rows multiply with number of columns.
• This can be mathematically represented as below:
• Total number of pixels = number of rows XX number of columns
• Or we can say that the number of x,y coordinate pairs make up the total number of pixels.
• We will look in more detail in the tutorial of image types, that how do we calculate the pixels in a color image.

### Gray level

• The value of the pixel at any point denotes the intensity of image at that location, and that is also known as gray level.
• We will see in more detail about the value of the pixels in the image storage and bits per pixel tutorial, but for now we will just look at the concept of only one pixel value.

### Pixel value 0.0

• As it has already been define in the beginning of this tutorial, that each pixel can have only one value and each value denotes the intensity of light at that point of the image.
• We will now look at a very unique value 0. The value 0 means absence of light. It means that 0 denotes dark, and it further means that when ever a pixel has a value of 0, it means at that point, black color would be formed.
• Have a look at this image matrix
 0 0 0 0 0 0 0 0 0
• Now this image matrix has all filled up with 0. All the pixels have a value of 0. If we were to calculate the total number of pixels form this matrix, this is how we are going to do it.
• Total no of pixels = total no. of rows X total no. of columns  = 3 X 3        = 9.
• It means that an image would be formed with 9 pixels, and that image would have a dimension of 3 rows and 3 column and most importantly that image would be black.  The resulting image that would be made would be something like this
• Now why is this image all black. Because all the pixels in the image had a value of 0.

### Concept of Bits per pixel

Bpp or bits per pixel denotes the number of bits per pixel. The number of different colors in an image is depends on the depth of color or bits per pixel.

Bits in mathematics:

Its just like playing with binary bits.

How many numbers can be represented by one bit. 0,1

How many two bits combinations can be made.

00,01,10,11

If we devise a formula for the calculation of total number of combinations that can be made from bit, it would be like this.

2^bpp

Where bpp denotes bits per pixel. Put 1 in the formula you get 2, put 2 in the formula, you get 4. It grows exponentially.

### Number of different colors:

Now as we said it in the beginning, that the number of different colors depend on the number of bits per pixel.

The table for some of the bits and their color is given below.

 Bits per pixel Number of colors 1 bpp 2 colors 2 bpp 4 colors 3 bpp 8 colors 4 bpp 16 colors 5 bpp 32 colors 6 bpp 64 colors 7 bpp 128 colors 8 bpp 256 colors 10 bpp 1024 colors 16 bpp 65536 colors 24 bpp 16777216 colors 16.7millioncolors16.7millioncolors 32 bpp 4294967296 colors 4294millioncolors4294millioncolors

This table shows different bits per pixel and the amount of color they contain.

You can easily notice the pattern of the exponentional growth. The famous gray scale image is of 8 bpp , means it has 256 different colors in it or 256 shades.

Color images are usually of the 24 bpp format, or 16 bpp.

We will see more about other color formats and image types in the tutorial of image types.

Color values:

We have previously seen in the tutorial of concept of pixel, that 0 pixel value denotes black color.

Black color:

Remember, 0 pixel value always denotes black color. But there is no fixed value that denotes white color.

White color:

The value that denotes white color can be calculated as :

In case of 1 bpp, 0 denotes black, and 1 denotes white.

In case 8 bpp, 0 denotes black, and 255 denotes white.

Gray color:

When you calculate the black and white color value, then you can calculate the pixel value of gray color.

Gray color is actually the mid point of black and white. That said,

In case of 8bpp, the pixel value that denotes gray color is 127 or 128bpp ifyoucountfrom1,notfrom0ifyoucountfrom1,notfrom0.

### Image storage requirements

After the discussion of bits per pixel, now we have every thing that we need to calculate a size of an image.

### Image size

The size of an image depends upon three things.

• Number of rows
• Number of columns
• Number of bits per pixel

The formula for calculating the size is given below.

Size of an image = rows * cols * bpp

It means that if you have an image, lets say the above figure 1:

Assuming it has 1024 rows and it has 1024 columns. And since it is a gray scale image, it has 256 different shades of gray or it has bits per pixel. Then putting these values in the formula, we get

Size of an image = rows * cols * bpp

= 1024 * 1024 * 8

= 8388608 bits.

But since its not a standard answer that we recognize, so will convert it into our format.

Converting it into bytes = 8388608 / 8 = 1048576 bytes.

Converting into kilo bytes = 1048576 / 1024 = 1024kb.

Converting into Mega bytes = 1024 / 1024 = 1 Mb.

Thats how an image size is calculated and it is stored. Now in the formula, if you are given the size of image and the bits per pixel, you can also calculate the rows and columns of the image

## Frequency Word for IELTS Listening

Frequency Word for IELTS Listening School a. Library  WordSentence1. Shelf 2. Librarian 3. The stacks 4. Return 5. Fine 6. Magazine 7. Copier  8. Overdue  9. Reading room  10. Reference...

## Chapter 8: Gantt chart Project Development in SDLC

Gantt chart Project DevelopmentSchedule (project management) The project scheduleis the tool that communicates what work needs to be performed, which resources of the organization will perform the work and the timeframes in which that work needs to be performed....

## Chapter 7: Feasibility Analysis in Software Develoment Life Cycle.

Feasibility AnalysisWhat is Feasibility Analysis?? An analysisand evaluation of a proposed project to determine if it (1) is technically feasible, (2) is feasible within the estimated cost, and (3) will be profitable for Organization. Feasibility analysis guides the...

## Chapter 6: Data Flow Diagram in Software Development Life Cycle.

Data Flow Diagram What is DFD? A data flow diagram (DFD) is a graphical representation of the "flow" of data through an information system, modelling its process aspects.A DFD is often used as a preliminary step to create an overview of the system, which can later be...

## Chapter 5: System request on SDLC

System Request In most organizations, project initiation begins by preparing a  system request. A  system request is a document that describes the business reasons for building a system and the value that the system is expected to provide.The project sponsor...

## Chapter 4: SDLC design Phase

SDLC design Phase DFD (Design Analysis)Architectural DesignUI DesignDatabase DesignProgram DesignArchitectural design (logical)Network designClient –server designClient designServer designCloud ComputingDatabase designER diagramRelational diagramDDL (not...

# You may find interest following article

## Frequency Word for IELTS Listening

Frequency Word for IELTS Listening School a. Library  WordSentence1. Shelf 2. Librarian 3. The stacks 4. Return 5. Fine 6. Magazine 7. Copier  8. Overdue  9. Reading room  10. Reference room  11. Periodical room  12. Study lounge  13. Catalogue  14....

## Chapter 8: Gantt chart Project Development in SDLC

Gantt chart Project DevelopmentSchedule (project management) The project scheduleis the tool that communicates what work needs to be performed, which resources of the organization will perform the work and the timeframes in which that work needs to be performed. The project scheduleshould reflect all of the work associated with delivering the project on time....

## Chapter 7: Feasibility Analysis in Software Develoment Life Cycle.

Feasibility AnalysisWhat is Feasibility Analysis?? An analysisand evaluation of a proposed project to determine if it (1) is technically feasible, (2) is feasible within the estimated cost, and (3) will be profitable for Organization. Feasibility analysis guides the organization in determining whether to proceed with the project. Feasibility analysis also identifies...

## Chapter 6: Data Flow Diagram in Software Development Life Cycle.

Data Flow Diagram What is DFD? A data flow diagram (DFD) is a graphical representation of the "flow" of data through an information system, modelling its process aspects.A DFD is often used as a preliminary step to create an overview of the system, which can later be elaborated.Show users how data moves between different processes in a system. Figure 1: DFD Symbols...

## Chapter 5: System request on SDLC

System Request In most organizations, project initiation begins by preparing a  system request. A  system request is a document that describes the business reasons for building a system and the value that the system is expected to provide.The project sponsor usually completes this form as part of a formal system project selection process within the...

## Chapter 4: SDLC design Phase

SDLC design Phase DFD (Design Analysis)Architectural DesignUI DesignDatabase DesignProgram DesignArchitectural design (logical)Network designClient –server designClient designServer designCloud ComputingDatabase designER diagramRelational diagramDDL (not now..!!)Program design (physical)Investigating the hardware/software platformPhysical DFDData storageData...

## Chapter 3: SDLC and its Life cycle Phases.

What is SDLC? The systems development life cycle (SDLC), also referred to as the application development life-cycle, is a term used in systems engineering, information systems and software engineering to describe a process for planning, creating, testing, and deploying an information system. Career Paths for System Developers Systems Development Life Cycle Building...

## Chapter 2: SDLC Key Features For SYSTEMS ANALYST.

Once upon a time, software development consisted of a programmer writing code to solve a problem or automate a procedure. Nowadays, systems are so big and complex that teams of architects, analysts, programmers, testers and users must work together to create the millions of lines of custom-written code that drive our enterprises.To manage this, a number of system...

## Chapter 1: System analysis and Design Overview.

System analysis, a method of studying a system by examining its component parts and their interactions. •It provides a framework in which judgments of the experts in different fields can be combined to determine what must be done, and what is the best way to accomplish it in light of current and future needs.  •The system analyst (usually a software engineer or...

## Chapter 4: Concept Of Sampling, Quantization And Resolutions

Concept Of Sampling, Quantization And Resolutions Conversion of analog signal to digital signal: The output of most of the image sensors is an analog signal, and we can not apply digital processing on it because we can not store it. We can not store it because it requires infinite memory to store a signal that can have infinite values. So we have to convert an...

## Chapter 3: Images and Conversions in Digital Image Process

Images And Conversions There are many type of images, and we will look in detail about different types of images, and the color distribution in them. The binary image The binary image as it name states, contain only two pixel values. 0 and 1. In our previous tutorial of bits per pixel, we have explained this in detail about the representation of pixel values to...

Vocabulary to show the sequence: You must write a summary of at least 150 words in response to a specific graph (bar, line, or pie graph), table, chart, or procedure in Writing Task 1 of the IELTS Academic test (how something works, how something is done). This job assesses your ability to choose and report the most important aspects, describe and compare data,...

## Part 5: IELTS Academic Writing Task 1 Formal and Informal expressions.

Formal and Informal expressions and words: You must write a summary of at least 150 words in response to a specific graph (bar, line, or pie graph), table, chart, or procedure on the IELTS Academic test (how something works, how something is done). Few more informal expressions with their formal versions are given below. Since IELTS is a formal test, your writing...

## Part 4: IELTS Academic Writing Task 1 For Graph Comparison Vocabulary

Vocabulary to represent comparison in graphs: Type Word(s) should be used Similar about / almost / nearly / roughly / approximately / around / just about / very nearly / Just over just above / just over / just bigger / just beyond / just across Just short just below / just beneath / just sort / just under / just a little Much more well above / well above / well...

## Part 3: IELTS Academic Writing Task 1 For Vocabulary Date month etc.

IELTS Academic Writing Task 1 For Vocabulary Date month From 1990 to 2000, Commencing from 1980, Between 1995 and 2005, After 2012. By 1995, In 1998, In February, Over the period, During the period, During 2011. In the first half of the year, For the first quarter, The last quarter of the year, During the first decade. In the 80s, In the 1980s, During the next 6...

The structure of the IELTS Academic Writing Task 1 (Report Writing): Introduction: Introduction (never copy word for word from the question) + Overview/ General trend (what the diagrams indicate at a first glance). Reporting Details: Main features in the Details + Comparison and Contrast of the data. (Do not give all the figures.) + Most striking features of the...

## Part 1: IELTS Writing Task 1 For Vocabulary

Vocabulary For Academic IELTS Writing Task 1 (part 1)  Academic IELTS Writing Task 1 question requires you to use several vocabularies to present the data given in a pie/ bar/ line/ mixed graph or to describe a process or a flow chart. Being able to use appropriate vocabularies, presenting the main trend, comparing & contrasting data and presenting thei logical...

## Chapter 1: Introduction To Digital Image Processing (DIP)

Introduction to DIP Signal processing is a discipline in electrical engineering and in mathematics that deals with analysis and processing of analog and digital signals , and deals with storing , filtering , and other operations on signals. These signals include transmission signals , sound or voice signals , image signals , and other signals etc. Out of all these...

## Part 10: DC – Network Addressing and Network Layer Routing

DC - Network Addressing Layer 3 network addressing is one of the major tasks of Network Layer. Network Addresses are always logical i.e. these are software based addresses which can be changed by appropriate configurations. A network address always points to host / node / server or it can represent a whole network. Network address is always configured on network...

## Part 9: Error Detection and Correction in Communication

DC - Error Detection & Correction There are many reasons such as noise, cross-talk etc., which may help data to get corrupted during transmission. The upper layers work on some generalized view of network architecture and are not aware of actual hardware data processing. Hence, the upper layers expect error-free transmission between the systems. Most of the...