i.fusion.hpf is an implementation of the High Pass Filter Additive (HPFA) Fusion Technique. It combines 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. Optionally, a linear histogram matching technique is performed in a way that matches the resulting Pan-Sharpened image to the statistical mean and standard deviation of the original multi-spectral image.


  1. Computing ratio of low (Multi-Spectral) to high (Panchromatic) resolutions
  2. High Pass Filtering the Panchromatic Image
  3. Resampling MSX image to the higher resolution
  4. Adding weighted High-Pass-Filetred image to the upsampled MSX image
  5. Optionally, matching histogram of Pansharpened image to the one of the original MSX image
+                                                                            +
| Pan Img ->  High Pass Filter  ->  HP Img                                   |
|                                      |                                     |
|                                      v                                     |
| MSx Img ->  Weighting Factors ->  Weighted HP Img                          |
|       |                              |                                     |
|       |                              v                                     |
|       +------------------------>  Addition to MSx Img  =>  Fused MSx Image |

Source: Gangkofner, 2008



The module is fairly easy to use. Arbitrary examples: Pansharpening of one band:
i.fusion.hpf pan=Panchromatic msx=Red

Pansharpening of multiple bands:

i.fusion.hpf pan=Panchromatic msx=Red,Green,Blue,NIR

Various illustrated examples detailed in the document i.fusion.hpf, implementation of the High Pass Filter Additive (HPFA) Image Fusion Technique (PDF)






Nikos Alexandris
Panagiotis Mavrogiorgos

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