Guessing the width of an image

Interpreting a 1-D array of pixels is not possible by the human eye. And yet such data is available in several circumstances, like the dump of pixel arrays from RAM or disk, the availability of image files in RAW format (without the width) or when solving a Capture-The-Flag cybersecurity challenge with images.

array availability capture capture-the-flag challenge cybersecurity data disk files flag human image images pixel