01What exactly is a pixel?
Pixel comes from “picture element”. In Chinese it is usually called 像素.
For a bitmap, a pixel is a record of the color at one position in an image.
One pixel
Records the color at one position
Many pixels
Arranged in rows and columns
02How do many pixels make an image?
A single pixel tells us almost nothing. But thousands of pixels arranged in a pattern can form a detailed scene.
Normal view
A complete little landscape
Zoomed in
You can see the individual squares
03What is inside one pixel?
The most important information in a pixel is its color. Many images use RGB: red, green and blue values combine to create a color.
This pixel
Is orange-red
When each channel uses 8 bits, the three RGB channels use 24 bits in total.
04How are resolution and pixels related?
Image resolution is often written as width × height. For example, 1920 × 1080 means 1,920 pixels across and 1,080 pixels down.
about 2.07 megapixels
A camera described as 12 MP has about 12 million pixels. MP means Megapixel.
05How large is one pixel?
This is easy to misunderstand: a pixel has no single physical size.
In a digital image, a pixel is a position in the image coordinates. It does not come with a fixed size such as 0.1 millimeters.
Image pixel
Only an image position
No fixed millimeter sizeScreen pixel
Has a physical size
Depends on screen size and pixel density06Are image pixels and screen pixels the same?
They are related, but they are not exactly the same idea.
Image pixel
One position in image data
Screen pixel
A real display unit
At 100% scale, one image pixel may roughly correspond to one screen pixel. When an image is enlarged, reduced or rotated, the graphics system recalculates the mapping.
One image pixel may be close to one screen pixel
One image pixel may cover more screen pixels
Several image pixels may influence one screen pixel
07Do more pixels always make a better image?
Not necessarily. More pixels can record more detail, but final image quality also depends on many other factors.
Pixel count
How many spatial samples the image records
Capture quality
The lens, sensor and shooting conditions
Compression
Heavy compression can lose detail
Color and bit depth
How much color information is recorded
What do you know now?
- A pixel is one image position in a bitmap and records color information.
- Photos and screenshots are made from many pixels arranged in rows and columns.
- A pixel commonly stores RGB information and may also include transparency.
- 1920 × 1080 is about 2.07 million pixels.
- MP means Megapixel; 12 MP is about 12 million pixels.
- Image pixels have no fixed millimeter size, while physical screen pixels do.
- Image pixels and screen pixels are different concepts connected by scaling.
- More pixels do not automatically mean better quality.
Next question: How can a computer use just red, green and blue numbers to create so many colors? Next: How computers use RGB to make colors.