The invention relates to a method for processing an image displayed by a display device comprising at least one light source and one light valve. It comprises the following steps: applying a compression factor C to the grey levels of the image video signal that are higher than a threshold value NG1, the said threshold value being lower than the peak grey level value (NGmax) of the image video signal, adjusting the luminance of the light produced by the light source to the luminance value corresponding to the peak grey level (NGmax) of the image after compression, multiplying the video signal delivered to the light valve by an expansion factor D equal to the ratio of the peak grey level of the image before compression (NGmax) over the peak grey level of the image after compression (NGmax).