Pixel

What is a Pixel?

A pixel is the smallest unit of a digital image or graphic that can be displayed and represented on a digital display. They serve as the building blocks of digital images, used to display everything from text to intricate graphics and photos.

Techopedia Explains the Pixel Meaning

A pixel, meaning a dot or square on a display screen, usually maintains a square shape with equal vertical and horizontal sampling pitches. However, in formats like anamorphic widescreen format, pixels may appear rectangular.

Each pixel has a unique logical address and is usually composed of eight bits or more. In most high-end devices, pixels can display millions of different colors, achieved by blending the three main components of the RGB color spectrum.

The amount of bytes allocated for each color component of a pixel varies depending on the color system used.

For example:

In 8-bit color systems, one byte per pixel is allocated, limiting the palette to 256 colors.
In 24-bit color systems, three bytes are allocated – one for each RGB color – allowing for 16,777,216 color variations.
A 30-bit deep color system allocates 10 bits per RGB color, yielding 1.073 billion color variations.

Despite these high color variations, the human eye can distinguish up to 10 million colors. Exceeding this range may not enhance detail and could lead to color banding issues.

History of Pixel

The pixel definition takes its meaning from a combination of two words: “picture” and “element.” It describes the smallest controllable element of a digital image on a display device. Over time, “picture element” was shortened to “pixel” (pix = picture, el = element) for convenience and has become the standard term in digital imaging and computer graphics.

How Pixel Works

Depending on the graphics card and display monitor, the quantity, size and color combination of pixels vary, and is measured in terms of display resolution. For example, a display resolution of 1280 x 768 will produce a maximum of 983,040 pixels on a screen.

The pixel resolution spread also determines the quality of the display; more pixels per inch of the display screen yields better images. For example, a 2.1 megapixel picture contains 2,073,600 pixels since it has a resolution of 1920 x 1080. A megapixel refers to one million pixels, indicating the resolution of digital images captured by cameras or displayed on screens.

The physical size of a pixel varies, depending on the display resolution. At maximum resolution, it matches the dot pitch size but increases at lower resolutions as each pixel covers more dots. This can make pixels visible, leading to a “pixelated” image. Additionally, within each pixel, subpixels – smaller units within a pixel that represent specific colors – enhance color accuracy and the overall quality of the image.

Difference Between PPI and DPI

Pixels Per Inch (PPI)

Used in digital screens.
Measures the density of pixels on a digital display.
The higher the PPI, the more detailed the image appears.

Dots Per Inch (DPI)

Associated with printers.
The number of individual dots of ink a printer can produce within a one-inch space.
A higher DPI indicates more detail in the printed output.

Pixels in Computer Graphics

In computer graphics, pixels are essential for determining both image clarity and detail – their arrangement and color composition define the visual quality displayed. Several key factors shape the quality and performance of these graphics.

For example:

Color depth

More colors per pixel enhance realism.

Hardware capabilities

Processing power is necessary for pixel manipulation.

Image compression

Can degrade pixel quality.

Pixel density (PPI)

Higher density improves clarity.

Rendering techniques

Influences texture and light interaction.

Subpixel arrangement

Affects color accuracy and sharpness.

Screen resolution

Higher resolutions offer finer details.

Examples of Pixels

Pixel Art: A form of digital art that employs a limited number of pixels to create stylized, nostalgic images reminiscent of early video games.

Smartphone Screens: Modern smartphone displays utilize millions of pixels to produce sharp, detailed images and videos.

Television Screens: TVs display images using pixels, and 4K models feature a horizontal resolution of approximately 4,000 pixels for high-definition clarity.

Examples of Pixels

Challenges of Scaling Pixels

Pixel scaling involves techniques to adjust digital images for various display resolutions, ensuring consistent quality across devices, from small smartphones to large televisions. However, improper scaling can lead to blurry, pixelated, or distorted images.

Methods used for image scaling include:

Interpolation-Based ScalingNon-Interpolation-Based Scaling

This method recalculates pixel values in a resized image using surrounding pixel data, ensuring a smooth transition of colors and details. Techniques include bilinear interpolation, bicubic interpolation, and Lanczos resampling.

This method either replicates existing pixels or uses simple operations to remove them. It is faster than interpolation methods but may result in more pixelated images when upscaling. Techniques include nearest neighbor, max pooling, and min pooling.

Tips on Using Pixels

Appropriate scaling

Choose a scaling method that meets the quality requirements of the project.

Device testing

Verify images on different devices to ensure consistent quality.

Manage color depth

Opt for higher color for precise color reproduction.

Select the right resolution

Choose a resolution suited to the intended use of the image.

The Bottom Line

Pixels, the smallest unit of an image or graphic displayed on digital screens, are key in digital imaging. They determine the clarity and detail of images, with their arrangement and colors defining visual quality. Techniques such as bilinear and bicubic interpolation effectively scale images. For optimal results, choose the appropriate resolution and test images on various devices.