MxNx3

MxNx3 is a notation for a three-dimensional array commonly used to represent color images. In this scheme, M is the image height and N is the width, while the final dimension of size 3 stores the color channels for each pixel.

The most common channel order is RGB, meaning that for a pixel at position (i, j) the array value is [R, G, B]. Some libraries use a different order, such as BGR, especially in OpenCV, so care is needed when exchanging data between tools. MxNx3 arrays are typically stored with 8-bit unsigned integers (0–255) per channel, but floating-point representations (0.0–1.0) are also common in image processing pipelines. The data layout is usually interleaved by pixel in the last dimension, i.e., the 3-channel vector belongs to each pixel, though some formats store separate planes for each channel.

MxNx3 is widely used for color images and for color frames in video processing, texture data in graphics, and synthetic datasets. Operations such as channel-wise normalization, color space conversion, and per-channel weighting assume the 3-channel structure. In contrast, grayscale images use MxN, and images with alpha channels use MxNx4. The term MxNx3 is a common building block in computer vision and image analysis tasks, reflecting the standard way color information is stored and manipulated in many software environments.