Enhancement of Digital Image Compression Using Discrete Cosine Transform - 2 Dimension (DCT - 2D)

Digital image compression is a data compression application that aims to reduce the redundancy of data so that the image can be stored and transmitted efficiently. There are two techniques in compression, namely lossless compression and lossy compression. In this research uses a compression technique with lossy compression using discrete cosine transform - 2 dimension (DCT-2D) method on the digital image size is limitted to 512x512 piksel bitmap image. The do a comparison percentage of the size of the compressed image based on 2x2 compression block, 4x4 compression block, and 8x8 compression block. Based on the research, digital image compresion algoritm using DCT-2D based compression blocks produce the best compression results percent more efficient to store based the compression of the size on the 8x8 compression block is 60.55%, the the compression block 2x2 is 48.09%, and compression block 4x4 is 50.94%. The best image quality of image compression on 2x2 blocks, where the image is still looks good by the human visual, the the best PSNR value is indicated by 8x8 compression block is 11.1849 dB. It proves that the percentage size image compression best results, do not determine the quality of the compressed image is the best image quality.