Remote Sensing Image Fusion Using Discrete Wavelet Transform and IHS Transformation

This code implements remote sensing image fusion based on discrete wavelet transform (DWT) and IHS transformation, primarily designed for integrating multispectral and panchromatic images. The implementation follows a systematic approach where DWT provides multi-scale decomposition and reconstruction capabilities, extracting different frequency components from images through pyramid-structured filtering operations. The IHS transformation module handles color space conversion, effectively separating intensity, hue, and saturation components. The algorithm workflow begins with applying DWT to both input images, decomposing them into approximation and detail coefficients at multiple resolution levels. The IHS transform then processes the multispectral image to extract its color information while utilizing the panchromatic image's high-resolution intensity component. The core fusion mechanism involves replacing the intensity component of the multispectral image with the enhanced panchromatic image data while preserving the original spectral characteristics. Key functions include wavelet decomposition using filter banks (such as Daubechies or Haar wavelets), IHS color space conversion matrices, and fusion rules that optimally combine high-frequency details from the panchromatic image with color information from the multispectral image. The reconstruction phase involves inverse DWT operations and reverse IHS transformation to generate the final fused image that maintains high spatial resolution with rich spectral content. The implementation includes parameter optimization for wavelet levels and fusion weighting factors to achieve optimal visual quality and quantitative metrics.