  The two-dimensional discrete cosine transform (DCT) can be found in the heart
of many image compression algorithms. Specifically, the JPEG format uses a
lossy form of compression based on that transform. Since the standardization of
the JPEG, many other transforms become practical in lossy data compression.
This article aims to analyze the use of these transforms as the DCT replacement
in the JPEG compression chain. Each transform is examined for different image
datasets and subsequently compared to other transforms using the peak
signal-to-noise ratio (PSNR). Our experiments show that an overlapping
variation of the DCT, the local cosine transform (LCT), overcame the original
block-wise transform at low bitrates. At high bitrates, the discrete wavelet
transform employing the Cohen-Daubechies-Feauveau 9/7 wavelet offers about the
same compression performance as the DCT.
