A method for compressingrestoring image data free from degradation of image quality caused by compressiondecompression, a method for compressing image data at high compression ratio, and its restoring method are disclosed. The main keyboard includes a first edge, first keys, and a first housing on the first edge. The third layer includes a polymeric material and a filler. A rivet of the rivet assembly is inserted into at least one object. The start point, the thickness, and line slope are utilized for estimating and mapping four corner points of the rectangular perimeter with respect to the orthogonal pel array.