# ToDo # HPF Resolution Merge --- Attempt to replicate in GRASS GIS # Function to combine high-resolution panchromatic data with lower resolution # multispectral data, resulting in an output with both excellent detail and # a realistic representation of original multispectral scene colors. # The process involves a convolution using a High Pass Filter (HPF) on the # high resolution data, then combining this with the lower resolution # multispectral data. Read the description of the Algorithm below. # Source: "Optimizing the High-Pass Filter Addition Technique for Image Fusion" # Ute G. Gangkofner, Pushkar S. Pradhan, and Derrold W. Holcomb (2008) # The general algorithm is: # 1. Read pixel sizes from Image files and calculate R, the ratio of # multispectral cell size to high-resolution cell size # 2. Apply the High-pass filter to the high spatial resolution image. # 3. Resample the Multi-Spectral image to the pixel size of the high-pass image. # Note, bilinear resampling required (4 nearest neighbours)! # 4. Add the HPF image weighted relative to the global standard deviation of # the Multi-Spectral band. # 5. Optionally, stretch linearly the new HPF-Sharpened image to match the mean and # standard deviation of the input Multi-Sectral image.