1. A method of imaging a biological tissue sample, the method comprising: acquiring image data from the biological tissue sample, the image data comprising a plurality of multi-spectral unprocessed pixels; performing a spectral unmixing of the plurality of multi-spectral unprocessed pixels, wherein performing the spectral unmixing comprises: selecting a first input pixel from the image data, processing the first input pixel with an unmixing algorithm to generate an unmixing result for the first input pixel, selecting, from the plurality of multi-spectral unprocessed pixels, a second pixel that meets a predefined similarity criterion with respect to the first input pixel, and reusing the unmixing result obtained for the first input pixel for unmixing the second pixel without processing the second input pixel with the unmixing algorithm; and outputting an output image of the biological tissue comprising a first unmixed pixel corresponding to the first input pixel and a second unmixed pixel corresponding to the second pixel.