The transfer of selected image data to a computer using a conductive tablet

The processing and analysis of images in a computer often requires the selection of particular features of a complex image for more detailed study. Sometimes such decisions are empirical, in which case it would be extremely difficult to describe a rigorous algorithm for detecting these features automatically in a computer. In this situation graphic tablets can be very useful as they allow an operator to use experience in deciding which features are to be transferred into a computer. A tablet is described which uses a conductive glass plate and pencil probe. A number of subroutines are available in a general purpose program for conventional processing, calculation and displays to be effected by simple option selection on the tablet. For specific applications in cell growth, modelling and three dimensional reconstruction of serial sections, special programs were developed which could include appropriate subroutines. The categorisation of subsections by an operator was particularly useful in allowing different methods of analysis and display to be applied to each. For example they could be displayed separately or given different density levels by choosing the appropriate option in the program.