An image comparing system acquires a pixel value of each pixel in two images, and obtains two groups of relative values corresponding to the two images respectively. A general video decoding device includes a second processor that generates a first portion of a decoded video signal from the first EDC data and that further generates a second portion of the decoded video signal from the second EDC data. The WPT sequentially parses a test condition to identify a PTM, a power coupling linkage between the WPT and the WPR, and a WPP of the WPR. The display device further includes a controller that generates a virtual keyboard image including a plurality of virtual keys for display on the display surface.