# Pixels: the small pieces of a picture

[Concepts explained](README.md)

A **pixel**, short for *picture element*, is one sample of color in a digital image. A small image is like a mosaic of colored tiles. Together the tiles make a picture.

The image's **resolution** describes its pixel dimensions. An image 32 pixels wide and 16 pixels high contains 512 pixel positions. That does not tell you its exact file size: the format, color data, and compression matter too.

## Image size and drawing size

A small image can be drawn larger on screen. Enlarging it does not create missing original detail. Depending on the renderer, the result may look blocky or smoothed.

Pliro's **logical coordinates** describe positions in its scene. They are not necessarily the same as physical screen pixels. A preview can scale a logical scene to fit a window or device. Mouse positions and drawing positions should use the same scene coordinate system.

## A paper experiment

Draw an eight-by-eight grid and color squares to make a turtle. Then draw each original square as a two-by-two group. Your enlarged picture has bigger squares but the same original pattern.

Images may also store **alpha**, information about transparency. Transparent parts can let the background show through. Transparency does not automatically decide whether game objects collide; collision rules use their own geometry.

[Coordinates](../guides/graphics.md) · [Colors](../guides/colors.md) · [Collisions](collision-detection.md)