Techniques of image processing are now accessible with personal computers. The initial phase of the processing is the digitalization of images. It can be achieved by the capture of a video signal, with a scanner or with a photographic CD. Digital images can undergo various processings (modifications of the pixels, filters, false color, superposition of images) whose purpose is to improve the quality of the documents or to show some details. It is fundamental for scientific documents to avoid the modification or the loss of the information during the processing. Techniques of image processing are going to know many applications in the exploitation of biological photographic documents.