Some experiments in compressing angiocardiographic images according to the Peano-Hilbert scan path

We defined and implemented three new irreversible compression techniques for digital angiocardiographic static images: brightness error limitation (BEL), pseudo-gradient adaptive brightness error limitation (PABEL), pseudo-gradient adaptive brightness and contrast error limitation (PABCEL). To scan digital images we implemented an algorithm based on the Peano-Hilbert plane filling curve. We applied our compression techniques to 168 static images selected from angiocardiographic 35-mm films. We achieved best compression results applying the PABCEL method, obtaining a mean compression ratio of about 8:1. Consulted cardiologists did not find significant diagnostic differences between original images and reconstructed ones.