Background: Optical imaging in underwater environment to monitor marine objects is now a hot topic of research which can be used for environmental healthcare systems through the underwater ecosystem. Among different areas of research, image coding techniques are widely applied to compress data for reliable communications such that we know one of the most challenges in underwater communications is to have a low bit rate in acoustic links particularly while doing imaging in deep waters (in this condition, light needed for imaging is provided by a battery).
Methods: Two dimensional Discrete Cosine Transform (2D-DCT) is the main technique that we use for image compression here, on which we test two different patch sizes in 2D-DCT to study of the patch size effect on quality of compression, execution time and preservation ability of high-frequency information in edges.
Results: The results clearly show results that a larger patch size can always be better in terms of computational complexity, quality of coded images and also edge preservation when we use DCT for the compression process.
Discussion: Although this research approves the approach of JPEG codec once again for using the largest sub-image block in image compression (in terms of similarity and complexity), however use of an edge preservation factor is a new finding for our research. On the other hand, using the biggest patch size is not a general approach for all image processing applications, because some researches have shown that smaller patch may be more effective for some other applications.