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Robert H. Eikelboom, Kanagasingam Yogesan, Chris J. Barry, Ian J. Constable, Mei–Ling Tay–Kearney, Ludmila Jitskaia, Philip H. House; Methods and Limits of Digital Image Compression of Retinal Images for Telemedicine. Invest. Ophthalmol. Vis. Sci. 2000;41(7):1916-1924.
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purpose. To investigate image compression of digital retinal images and the
effect of various levels of compression on the quality of the images.
methods. JPEG (Joint Photographic Experts Group) and Wavelet image compression
techniques were applied in five different levels to 11 eyes with subtle
retinal abnormalities and to 4 normal eyes. Image quality was assessed
by four different methods: calculation of the root mean square (RMS)
error between the original and compressed image, determining the level
of arteriole branching, identification of retinal abnormalities by
experienced observers, and a subjective assessment of overall image
quality. To verify the techniques used and findings, a second set of
retinal images was assessed by calculation of RMS error and overall
results. Plots and tabulations of the data as a function of the final image size
showed that when the original image size of 1.5 MB was reduced to 29 KB
using JPEG compression, there was no serious degradation in quality.
The smallest Wavelet compressed images in this study (15 KB) were
generally still of acceptable quality.
conclusions. For situations where digital image transmission time and costs should
be minimized, Wavelet image compression to 15 KB is recommended,
although there is a slight cost of computational time. Where
computational time should be minimized, and to remain compatible with
other imaging systems, the use of JPEG compression to 29 KB is an
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