Sample (graphics) facts for kids
In computer graphics, a sample is like a tiny piece of information that helps make up a pixel on your screen. Think of a pixel as a tiny square, and a sample is a specific part of that square that holds details about one color, like red, green, or blue.
The picture below shows a 24-bit pixel. This means it uses 24 tiny pieces of digital information (called bits) to store its color. In this example, the pixel has three samples: one for Red, one for Green, and one for Blue.
In this specific example, the Red sample uses 9 bits, the Green sample uses 7 bits, and the Blue sample uses 8 bits. If you add them up (9 + 7 + 8), you get 24 bits in total for that one pixel! It's important to know that these samples don't always have to be the same size, and sometimes a pixel might not even have all three color samples.
Also, some pixels can have more than three samples. For example, the RGBA color space uses four samples: Red, Green, Blue, and an extra one called Alpha. The Alpha sample controls how transparent or see-through a pixel is.
A sample is very similar to a subpixel you might find on a physical display, like your TV or phone screen.
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What is a Digital Image Sample?
A digital image is made up of many tiny squares called pixels. Each pixel needs to know what color it should be. That's where samples come in! A sample is a specific part of a pixel that holds information about one of its color channels.
Imagine you're mixing paint. You might have a separate container for red, blue, and yellow. In digital images, these "containers" for color information are called channels. For example, a common way to store color is using Red, Green, and Blue (RGB) channels. Each of these channels has its own sample within a pixel.
Pixels and Their Building Blocks
A pixel is the smallest building block of a digital image or display. The word "pixel" comes from "picture element." If you look very closely at a TV or computer screen, you might see these tiny squares. Millions of pixels work together to create the images you see.
But a pixel isn't just one solid block of color. It's actually made up of smaller pieces of information, and these pieces are what we call samples. Each sample tells the pixel how much of a certain color it should display.
Color Channels: The Recipe for Color
To create all the different colors you see on a screen, digital images use color channels. The most common channels are Red, Green, and Blue (RGB). These are the primary colors of light. By mixing different amounts of red, green, and blue light, a pixel can create almost any color.
- Red Channel: This sample tells the pixel how much red light to show.
- Green Channel: This sample tells the pixel how much green light to show.
- Blue Channel: This sample tells the pixel how much blue light to show.
When you combine the information from the Red, Green, and Blue samples, the pixel knows exactly what color to display. For example, if all three samples are at their highest level, the pixel will be white. If all are at their lowest, it will be black.
What About the Alpha Channel?
Sometimes, you'll hear about a fourth channel called the Alpha channel. This channel doesn't deal with color directly. Instead, it controls the transparency or opaqueness of a pixel.
- If a pixel's Alpha sample is set to full, the pixel is completely solid (not see-through).
- If the Alpha sample is set to zero, the pixel is completely transparent (you can see right through it).
- Values in between make the pixel partly transparent, like frosted glass.
This is super useful for things like images with clear backgrounds, like logos or special effects in games, where you want to see what's behind the image.
How Bits Store Sample Information
You might have heard of "bits" when talking about computers. A bit is the smallest piece of information a computer can understand, either a 0 or a 1. Samples use bits to store their color or transparency information.
The more bits a sample has, the more different shades or levels of that color it can represent. For example:
- If a sample uses 8 bits, it can represent 256 different levels for that color (from 0 to 255). This means 256 shades of red, 256 shades of green, and 256 shades of blue.
- When you combine 8 bits for Red, 8 for Green, and 8 for Blue, you get a total of 24 bits per pixel. This is very common and allows for over 16 million different colors (256 x 256 x 256)! That's why images often look so smooth and realistic.
Sometimes, samples don't use the same number of bits. As seen in the example picture, the Red sample used 9 bits, Green used 7, and Blue used 8. This is less common but shows that the sizes can be flexible depending on how the image is stored.
Samples and Subpixels on Your Screen
When you look at a physical screen, like on your phone or computer, each pixel is actually made up of tiny lights called subpixels. Usually, there's a red subpixel, a green subpixel, and a blue subpixel for each pixel.
The samples in the digital image tell these physical subpixels how brightly to light up. So, the Red sample's value tells the red subpixel how much red light to emit, and so on. This is how the digital information from the samples gets turned into the colors you actually see on your screen!
