How the digital images are formed?

Images for Computers are nothing but bunch of 2D and 3D arrays. These arrays are stored as pixels (Picture Elements). Just a close look at any picture reveals that the picture is made up of very tiny elements (pixels).

Here is a picture depicting the pixels of an image

Now the question is how these images are formed?

The typical digital cameras have sensors in them that sense the objects. Light that falls upon objects is sensed by them and provide as a voltage form to the inner part of the camera. How that stuff is done? well that is beyond the scope of this article. Following image shows this scenario.

After sensing next phase is of managing image by its pixels. every sensor of the camera provides one pixel of image and hence the image is formed. These pixels are counted as Mega Pixels. 5 mega pixel camera, for example, has 5 million pixels in a single image.
Here we face a problem. the objects that we see with our eyes have large diversified number of colors and pixels. Due to the limitations of digital cameras it is impossible to catch every single pixel of object. To over come this problem there are few techniques that are helpful. two of them are defined as

• Sampling
• Quantization 

Lets understand these one at a time.
So far we know that the pixels of real object are impossible for digital cameras to sense. That's why a small distance is kept for object's pixel calculation lets say every 5th or 10th pixel of object is sensed and rest of them are ignored hence an image is obtained with fewer pixels than the original one had this process is known as Sampling.

  That was sampling the next techniques is of quantization. This techniques is for the limitation of colors sensors can have. there are a lots of color variations between blue and lighter blue. Even the human eye can not differentiate between them so does can't the sensors. that's why the sensors are program to show one color for different verities of blue to light blue this process is called quantization. 

This is how images are formed in digital cameras. In short continuous image is made discrete.