What is Pixel in Computer Graphics?

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What Does Pixel Mean


You might have seen small squares or dots when you zoom in the pictures. Those small dots are known as pixels. If you are curious to know about why those small dots in the image makes up the whole colored picture then you are at the right place. Images are stored in form of 0s and 1s and that are represented by a pixel. Image is broken down into tiny units called pixel and is stored into computer memory in form of binary digit.

In this article, you will learn everything about pixel.

What is a Pixel?

Pixel’s full form is “Picture Element”, which is also known as “PEL”. It is the smallest unit of any picture. You can think of an image, as the collection of pixels on a computer display, whether they are LCD or CRT monitors. A screen is made up of a grid of thousands or millions of pixels. A pixel is described with a dot or a square on a computer screen. Each pixel holds a unique value, or to be specific we can say a logical address. Pixel can have only one color at a time. Color of pixel in computer graphics depends upon the number of bits used to represent it.

Pixel cannot be seen as they are very small in size and it is the reason of high quality picture. Now, we are discussing about high quality picture, so let’s talk about what resolution is? Resolution of a computer screen depends upon size, color, and combination of pixels. More the resolution better your picture quality will be.

Another important concept in pixel resolution is aspect ratio. Have a look on aspect ratio too.

Aspect ratio

Aspect ratio is the ratio between width and height of the image grid. It is generally written as two numbers separated by colon (8:9). This ratio differs according to different images and screen sizes. The common aspect ratios are:

1.33:1, 1.37:1, 1.43:1, 1.50:1, 1.56:1, 1.66:1, 1.75:1, 1.78:1 etc .

Aspect ratio maintains the balance between the appearances of an image on the screen. Aspect ratio maintains the ratio between horizontal and vertical pixels. It does not let the image to get distorted when aspect ratio is increased.

How are pixels calculated?

The resolution of a computer screen indicates how many pixels are contained in a screen. So, a 1920*1080 display is a rectangular grid that’s just 1090 pixels tall and 1980 pixels wide. The number of pixels in a display is calculated by multiplying the height of grid by the width.

In the case of 1920*1080 display, there are a total of 2,073,600 pixels.

Screens with high-density pixel grids make it impossible to detect individual pixel with the naked eye, resulting in a sharp and crisp display.

Screens with lower densities produce weird and difficult-to-make-out images.

Types of pixels

There are many different types of pixels in computer graphics for example, subpixels, megapixels and pixels used for digital images. All of them are used for different things. Let’s talk about them in brief:

Subpixels – Subpixels is the subdivision of a pixel that is used to show amount of red, green or blue at a location.

Megapixels – A megapixel is equal to the 1 million regular pixels.

Digital Images- Digital Images are the electronic snapshots taken of a screen or scanned from documents.  The digital image is sampled and mapped as a grid of dots or picture elements (pixels). Each pixel is assigned a value (black, white, shades of gray or color), which is represented in binary digit (zeros and ones). The binary digits or bits for each pixel are stored in a sequence by a computer and often reduced to a mathematical code. The bits are then interpreted and read by the computer to produce an analog version for display or printing.     

A pixel is the collections of bits, and the number of bits defines the shade or color of the image. Let’s discuss about bits per pixel or bpp to know about the colors a screen can support.

Introduction to Bits Per Pixel (BPP)

 BPP or Bits per Pixel denotes the number of bits per pixel and the number depends on the depth of color or BPP. Bit is the binary digit (0 or 1) which is the smallest unit of data in the computer. Following are the number of different colors based on bits per pixel or bpp:

1 bpp = 2^1 colors, 2 bpp = 2^2 colors and soon.

Bits per pixel (bpp) Number of colors or shades
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
24 bpp 16777216 colors (16.7 million colors)

So, from the above table you can clearly notice number of colors = 2^bpp.

Image size depends on three things and they are as following:

  1. Number of rows
  2. Number of columns
  3. Number of bits per pixel

The formula for calculating the image size is:

 Size of image = rows * cols * bpp

For example:

Let rows be 3000 and cols be 1687, and bpp is 256.

Size of image = rows * cols * bpp

                     = 3000 * 1687 * 8

                     = 40488000 bits

Converting 40488000 bits into bytes = 40488000 / 8 = 5061000 bytes.

Converting 5061000 bytes into kilobytes (KB) = 5061000 / (2^10) = 4942 KB.

Converting 4942 KB into megabytes (MB) = 632625 / (2^10) = 4 MB.

Wrap Up

A screen is made up of a matrix of thousands or millions of pixels. Each pixel holds a unique value, or to be specific we can say a logical address. It can have only one color at a time. Color of pixel in computer graphics depends upon the number of bits used to represent it. Total number of pixel is the product of number of rows and number of columns of the grid. The number of dots or pixel per inch tells about the resolution. More the number of pixels at a position, more the resolution will be.

Resolution of a computer screen depends upon size, color, and combination of pixels. More the resolution better your picture quality will be. There are different types of pixels – subpixels and megapixels. Subpixels are the subdivision of a pixel, typically used to show amount of red, green or blue at a location. A megapixel is equal to one million regular pixels.

A pixel is the collections of bits, and the number of bits defines the shade or color of the image. Bits per Pixel denotes the number of bits per pixel and the number depends on the depth of color or BPP whereas, number of colors = 2^bpp.

If the bpp is 9 then how many colors does the computer supports? 

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