Image Pixel Reader

A pixel (short for picture element) is the smallest element of a raster image to which a color can be assigned.

A digital image is composed of a grid of pixels arranged in rows and columns. Each pixel contains information that allows it to represent a color.

Pixels exist only in raster images (JPG, PNG, GIF, BMP, etc.). Vector images use mathematical shapes (lines, curves, polygons) and are therefore not composed of pixels.

The image must be decoded into a readable raster format (JPG, PNG, GIF, BMP, etc.) in order to access its pixels, its width (number of columns) and its height (number of rows).

The pixel reading is usually a number, it can be associated with a table of contents (if the colors are indexed) or with an N-bit value (usually 24 bits).

This number can then be translated into 3 components: Red, Green and Blue.

Extracting pixels from an image involves reading each pixel one by one in order to retrieve its color and position.

To extract all the pixels having a given color, read all the values of each pixel and note their coordinates (rows, columns).

Some images use an alpha channel to manage transparency.

In this case, a pixel no longer contains only the Red, Green, and Blue components, but also a fourth component: Alpha.

The Alpha value indicates the level of transparency: 0 for completely transparent, and 255 for completely opaque.

Even when a pixel is invisible on the screen (alpha at 0), its RGB components can still contain a usable color during image processing.

In computing, arrays and memory locations generally start at index 0 rather than 1.

This convention simplifies memory address calculations and makes it easier to locate the position of elements within a data array.

Most software will then note the first pixel (ie. reading the top left pixel) with coordinates (x = 0, y = 0).