Why a DICOM image can provide dimension of the image in mm and a JPEG image can only provide image dimension in number of rows and columns?

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  • 6 months ago

    DICOM images are produced by things like MRIs that take precise measurements at specific intervals and distances from known reference points. The purpose of JPEG is first and foremost to provide an attractive image, not scientific, medical, or engineering documentation where scale or distance is important.

    JPEG images do, of course, have an Exif data field where data about timing, aperture size, lens, GPS location, etc... can be stored, but it's up to the camera to provide that data.

    • 6 months agoReport

      Don't forget that JPEG always compresses (you cannot turn compression off) so it ALWAYS distorts the image.

  • 6 months ago

    JPEG does allow specifying a physical image size, indirectly through pixel density fields coded either as pixels per inch or pixels per cm. It's in the metadata, if an application wants to use it.

    It's really a non-issue for photographic image files, though, and that's what JPEG/JFIF was designed for. The physical size of an image rendered on phone is not the same as the same image on a stadium display. If you take a picture of Mt. Fuji, the camera has no way to capture the physical size of the mountain. And so on... The image is the image...a raster array of pixels, and how you scale it when rendering or interpret dimensions algorithmically in code are both application-dependent.

  • Anonymous
    6 months ago

    Because a jpeg is a very crappy image format that everyone agrees is useless while DICOM was SPECIFICALLY created for medical purposes and high fidelity images.

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