Automatically determining the dimensions of digitally stored images

Michael G. Evanoff; William J. Dallas; Melissa J. Bjelland

doi:10.1117/12.274081

25 April 1997 Automatically determining the dimensions of digitally stored images

Michael G. Evanoff, William J. Dallas, Melissa J. Bjelland

Proceedings Volume 3034, Medical Imaging 1997: Image Processing; (1997) https://doi.org/10.1117/12.274081
Event: Medical Imaging 1997, 1997, Newport Beach, CA, United States

Abstract

We frequently encounter digitally stored images whose formatting information, the number of lines and pixels, has been lost. Without the formatting information the image becomes practically inaccessible. Formatting loss can be caused by: (1) Legacy images - they come somewhere from the dim past; (2) Image acquisition devices that do not store the dimensions; (3) The proliferation of storage standards using headers that require software for new formats. In order to use the image, the dimensions must be recovered. We developed a robust method that determines the width and height of images stored in lexicographic order. We constructed an approximately periodic function from contiguous image data. Similar to a periodic function, the auto-correlation function of the contiguous data exhibits peaks spaced with a period that is equal to the width of the images. The height is determined by dividing the file's size by the width. We tested the algorithm on 42 medical images and one aerial photo. We created a larger test base by cropping regions of different sizes from the images and sub- sampling the images into several sizes. The algorithm found the correct dimensions in all cases except one - when the region consisted of periodic data. In this case, the auto- correlation function has peaks due to the periodicity of the data that cannot be discerned form the periodicity of the line lengths since all the peaks of the auto-correlation function are equal. The algorithm cannot discern the correct width among the ambiguous peaks. In practice, periodicity will never happen in real medical images.

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Michael G. Evanoff, William J. Dallas, and Melissa J. Bjelland "Automatically determining the dimensions of digitally stored images", Proc. SPIE 3034, Medical Imaging 1997: Image Processing, (25 April 1997); https://doi.org/10.1117/12.274081

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KEYWORDS

Medical imaging

Fourier transforms

Linear filtering

Algorithm development

Chest imaging

Image acquisition

Analog electronics

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