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pixel

 in full picture element

Smallest resolved unit of a video image that has specific luminescence and colour. Its proportions are determined by the number of lines making up the scanning raster (the pattern of dots that form the image) and the resolution along each line. In the most common form of computer graphics, the thousands of tiny pixels that make up an individual image are projected onto a display screen as illuminated dots that from a distance appear as a continuous image. An electron beam creates the grid of pixels by tracing each horizontal line from left to right, one pixel at a time, from the top line to the bottom line. A pixel may also be the smallest element of a light-sensitive device, such as cameras that use charge-coupled devices (see CCD).

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(PIX [picture] ELement) Generally, the smallest addressable unit on a display screen or bitmapped image. Screens are rated by their number of horizontal and vertical pixels; for example, 1024x768 means 1024 pixels are displayed in each row, and there are 768 rows (lines). Likewise, bitmapped images are sized in pixels: a 350x250 image has 350 pixels across and 250 down.

With color systems, each pixel contains red, green and blue subpixels, and the subpixel is actually the smallest addressable unit. The monitor's circuits address subpixels, and the software may also. When referring to hardware at the lowest level, the term "pixel" often really refers to "subpixel." See dead pixel.

Pixel Structures
In storage, pixels are made up of one or more bits. The greater this "bit depth," the more shades or colors can be represented. The most economical system is monochrome, which uses one bit per pixel (on/off). Gray scale and color typically use 4 to 24 bits per pixel, providing 16 to 16 million colors. See bit depth.

Displaying the Pixel
On a display screen, pixels are either phosphor or liquid crystal elements. For monochrome, the element is either energized fully or not. For gray scale, the pixel is energized with different intensities, creating a range from light to dark. For color displays, the red, green and blue subpixels are each energized to a particular intensity, and the combination of the three color intensities creates the perceived color to the eye. See resolution and vertex shader.

A Monochrome Bitmap

The simplest pixel representation is a black and white monochrome image in which one bit represents one pixel. Monochrome CRTs use white, green or amber phosphors as a single color over a gray/black screen background.

Pixel Resolutions

These are the primary resolutions displayed on a PC. With more pixels on screen, more of the document is visible, but the text and images will appear smaller.

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pixel - picture element