Every digital image is made up of many little dots that are actually color samples called pixels.You can find out the number of pixels in a graphic by right-clicking it. The term "pixel" means picture element. Resolution refers to the pixel dimensions of height and width on a computer screen. Higher resolution and sharper picture quality occurs when pixels per inch increase.
A pixel is the smallest unit of a graphic image on a CRT or LCD monitor, and looks like a microscopic one color dot. Thousands of pixels fill up a screen that displays colorful computer graphics. Typical digital photos are composed of 24-bit pixels with 8 bits for each of the three primary colors: red, blue and green. A pixel can be one of more than 16 million colors. The pixel size of a graphic image is not absolute and can be adjusted by the user.
A computer screen is a matrix of pixels with addresses defined by coordinates. Thousands of pixels come together to create the appearance of shapes, colors and blends. If you count all the pixels across and down the screen you get height and width dimensions that you can adjust. Setting the monitor to a low resolution such as 640 by 480 makes individual pixels visible. Lower resolution settings will enlarge the pixels whereas higher resolution such as 800 by 600 displays a greater number of smaller pixels.
Resolution can be expressed as pixel density, measured in pixels per inch. As LCD technology improves, resolution has been increasing even on smaller gadget screens. Calculating the pixel density of a screen can be done by adding the squares of the width and height then finding the square root of that number, resulting in the diagonal pixel resolution. Then divide the diagonal pixel resolution by the display size and that will tell you the PPI for that device. A 240-inch monitor typically has a pixel density of 94 PPI.
When a graphic image exists as a digital file displayed on a monitor it is measured in pixels per inch. But when the image is printed it is measured in dots per inch. PPI and DPI do not mean the same thing, although they are commonly used interchangeably. Confusiion has also persisted between display resolution, measured by PPI, and image resolution, measured by DPI. The word "pixel" has various uses and connotations due to being used in print, computers and digital cameras.
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