With the rapid development of the Internet of Things (IoT), the secure transmission and storage of image data in resource-constrained devices has become an urgent challenge. Traditional cryptographic algorithms are often computationally intensive and unsuitable for IoT devices that require lightweight and efficient security solutions. To address this issue, this paper proposes a lightweight image encryption algorithm based on a two-dimensional cosine-coupled chaotic map (2D-CCM). By constructing a high-complexity chaotic system and generating pseudo-random sequences, the algorithm performs pixel-level scrambling and multi-round diffusion to enhance encryption strength and resistance to attacks. Experimental results demonstrate that the proposed method exhibits strong robustness against cropping and noise interference, while significantly reducing encryption and decryption time compared to existing methods. These features make it well-suited for secure image processing in IoT applications such as smart sensing and edge computing.