A computer implemented method uploads image data to a remote computer such as a server by: defining an area in a user interface adapted to receive an image; generating a thumbnail associated with the image when the image is associated with the area; and, uploading the image to the server. The described method of spectrum sharing, called On-Demand Spectrum Contention, integrates Dynamic Frequency Selection and Transmission Power Control with iterative on-demand spectrum contentions and provides fairness, adaptability, and efficiency of spectrum access for dynamic spectrum access systems using active inter-system coordination. The method can include a carrying procedure for passing the sheet between the rolls, then carrying the sheet along a peripheral face of one of the rolls, and then pulling out the sheet from the peripheral face.