How a screen builds pictures from pixels
A digital image is arranged as a grid of pixels, each carrying colour information. Many colour displays produce a pixel's appearance using red, green and blue subpixels at different intensities. From a normal viewing distance, your eyes combine their light into the colours and shapes of the larger picture.
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A grid of controlled light
A raster image stores colour information for positions in a rectangular grid. Each position is a pixel. The display uses that information to produce a pattern of light.
Many screens use red, green and blue subpixels. Adjusting their intensities creates different colour mixtures. Bright red and green light together can appear yellow, even though the display may not have a dedicated yellow subpixel there.
An image pixel and a physical screen pixel are not always matched one to one. Scaling can spread one image pixel across several display pixels or combine information from several image pixels.
- Image dimensions describe the stored grid.
- Screen dimensions describe the display's available grid.
- Scaling determines how one maps onto the other.
Enlarging a small image does not automatically reveal detail that its original grid never recorded.