Thumbnails are small images, pictograms or reduced images from the pages of a document.
The guessed object number of this image can be used as thumbnail. Secondly I do not want to guess any object numbers. The user produces from his TeX source a PDF file. The program 'thumbpdf.tex' looks for files with names 'thumb000.png' to 'thumb999.png' and additional ones specified in 'thumbopt.tex'. Then the above generated pdf file is parsed to get the object representation of the thumbnails.