1. Pixel, Resolution, Image Size
Computer Graphics

2. Content Pixel Resolution File Size
Relationship among resolution, filesize

3. Pixel
A pixel is the smallest unit of a digital image or graphic that can be displayed and represented on a digital display device.
A pixel is also known as a picture element.

4. Pixel
A pixel is represented by a dot or square on a computer monitor display screen.
Depending on the graphics card and display monitor, the quantity, size and color combination of pixels varies and is measured in terms of the display resolution.
Each pixel has a unique logical address, a size of eight bits or more and, in most high-end display devices, the ability to project millions of different colors.
The pixel resolution spread also determines the quality of display; more pixels per inch of monitor screen yields better image results.

5. Resolution
It is the number of pixels  (individual points of color) contained on a display monitor.
It is expressed in terms of the number of pixels on the horizontal axis and the number on the vertical axis.
The same pixel resolution will be sharper on a smaller monitor and gradually lose sharpness on larger monitors because the same number of pixels are being spread out over a larger number of inches. 

6. Resolution

7. Resolution
Display resolution is not measured in dots per inch as it usually is with printers. 
The resolution and the physical monitor size together do let you determine the pixels per inch.

8. File Size
The file size of an image is the digital size of the image file, measured in kilobytes (K), megabytes (MB), or gigabytes (GB).
File size is proportional to the pixel dimensions of the image.
Images with more pixels may produce more detail at a given printed size, but they require more disk space to store and may be slower to edit and print. 
Image resolution thus becomes a compromise between image quality (capturing all the data you need) and file size.

9. File Size
Another factor that affects file size is file format. Because of the varying compression methods used by GIF, JPEG, PNG, and TIFF file formats, file sizes can vary considerably for the same pixel dimensions. 
Color bit-depth and the number of layers and channels in an image affect file size.

10. Relationship
The more pixels per inch, the greater the resolution. Generally, an image with a higher resolution produces a better printed image quality.

11. Relationship
A 620‑ by 400‑pixel image displayed on monitors of various sizes and resolutions.

12. Relationship Resolution File Size Output HIGH MORE GOOD LOW LESS POOR
File Size and Output
Resolution

13. Image File Format