This document discusses digital image processing for remote sensing. It begins by defining a digital image as a discretized representation of the real world with light energy quantized to finite levels. It then describes the digitization process which involves sampling, quantization, and encoding. Sampling involves dividing the image area into a grid of cells called pixels. Quantization converts light energy to digital signals using an analog-to-digital converter (ADC) that assigns numeric values. Encoding represents the quantized values in binary. Digital image processing is useful for remote sensing as it allows flexibility, standardization, handling large data volumes, and removing distortions compared to human analysis.