Digital images are composed of pixels arranged in a grid, with each pixel represented by values for red, green, and blue light. The resolution of an image refers to the number of pixels per inch, which impacts the level of detail visible. Image size is measured by the number of pixels, while resolution impacts the physical size at which the image can be printed clearly. The appropriate resolution depends on the intended use of the image, such as printing, viewing on screen, or sharing online.

1. Resizing Digital Images By John Munno

3. On the left the full image, on the right the area in the red square magnified to show individual pixels

11. Image Sizing dialogue box

18. Save for web dialogue box

23. Image Sizing dialogue box