A method of generating a simulated digital bright field IHC or ISH image from digital, monochromatic, fluorescence images (106.1-106.7) of a tissue sample, the tissue sample comprising one or more stained biomarkers, each of the stained biomarkers being stained by a respective fluorescence stain, the method being performed by an image processing system and comprising: - generating at least a first one of the fluorescence images and generating a second one of the fluorescence images for each of the stained biomarkers, the pixel intensities of the first image being generically indicative of the presence of biological matter, the pixel intensities of each second image being selectively indicative of fluorescence signals emitted by the fluorescence stain that selectively stains said biomarker, the generation of the first and second images comprising performing spectral unmixing of a multi-spectral digital image of the tissue sample, the generation further comprising: - receiving an autofluorescence reference spectrum of the tissue sample or of a similar tissue sample and using the autofluorescence reference spectrum in the spectral unmixing for the generation of the first image; or receiving a first fluorescence reference spectrum of the first stain which generically binds to biological matter of the tissue sample; and using said first received fluorescence reference spectrum in the spectral unmixing for the generation of the first image; and - receiving a second fluorescence reference spectrum of each of the fluorescence stains used for staining the one or more biomarkers; and using each of the received second fluorescence reference spectra for the generation of a respective one of the one or more monochromatic second image; - receiving the first fluorescence image of the tissue sample, - transforming the first image into a transformed first image having a first color; - for each of the stained biomarkers, receiving the respectively created second fluorescence image of the tissue sample, - transforming each of the second images into a respective transformed second image having a respective second color; - overlaying and combining the transformed first and one or more second images; - storing the combined image as the simulated digital bright field IHC or ISH image in a storage medium; and/or - displaying the combined image as the simulated digital bright field IHC or ISH image on a display device. - generating at least a first one of the fluorescence images and generating a second one of the fluorescence images for each of the stained biomarkers, the pixel intensities of the first image being generically indicative of the presence of biological matter, the pixel intensities of each second image being selectively indicative of fluorescence signals emitted by the fluorescence stain that selectively stains said biomarker, the generation of the first and second images comprising performing spectral unmixing of a multi-spectral digital image of the tissue sample, the generation further comprising: - receiving an autofluorescence reference spectrum of the tissue sample or of a similar tissue sample and using the autofluorescence reference spectrum in the spectral unmixing for the generation of the first image; or receiving a first fluorescence reference spectrum of the first stain which generically binds to biological matter of the tissue sample; and using said first received fluorescence reference spectrum in the spectral unmixing for the generation of the first image; and - receiving a second fluorescence reference spectrum of each of the fluorescence stains used for staining the one or more biomarkers; and using each of the received second fluorescence reference spectra for the generation of a respective one of the one or more monochromatic second image; - receiving an autofluorescence reference spectrum of the tissue sample or of a similar tissue sample and using the autofluorescence reference spectrum in the spectral unmixing for the generation of the first image; or receiving a first fluorescence reference spectrum of the first stain which generically binds to biological matter of the tissue sample; and using said first received fluorescence reference spectrum in the spectral unmixing for the generation of the first image; and - receiving a second fluorescence reference spectrum of each of the fluorescence stains used for staining the one or more biomarkers; and using each of the received second fluorescence reference spectra for the generation of a respective one of the one or more monochromatic second image; - receiving the first fluorescence image of the tissue sample, - transforming the first image into a transformed first image having a first color; - for each of the stained biomarkers, receiving the respectively created second fluorescence image of the tissue sample, - transforming each of the second images into a respective transformed second image having a respective second color; - overlaying and combining the transformed first and one or more second images; - storing the combined image as the simulated digital bright field IHC or ISH image in a storage medium; and/or - displaying the combined image as the simulated digital bright field IHC or ISH image on a display device.