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What is the term for this image processing?

  1. Jan 27, 2015 #1
    How do you call of the digital image processing that simplifies an image by reducing the amount of pixels?

    I thought of the word “thinning”. But according to ”Fundamentals of Digital Image Processing” by Anil K. Jain, “Thinning algorithm transforms an object to a set of simple digital arcs, which lie roughly along their medial axes” while the processing I am searching a term has nothing to do with medial axes. Instead, it eliminates pixels in a consistent balance (e.g,.one pixel in every three pixels).

    Any suggestion/ insight will be much appreciated.
    Also, are “simple digital arcs” in the quote equivalent to edges?

    Thank you in advance.
  2. jcsd
  3. Jan 27, 2015 #2
    A few terms come to mind: coarsening, rescaling, or interpolating. Don't quote me though.
  4. Jan 27, 2015 #3


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    How about "compression"?
  5. Jan 27, 2015 #4
    That was the first thing that came to my mind, but I think that has to do with storing the file on disk more efficiently. I think the process we are describing might be considered a type of compression, but not all compression is rescaling. For instance, some compression is lossless.
  6. Jan 27, 2015 #5
    How about "downsampling"? For an image, it would only take the Nth pixel in a group of pixels, but that seems not to be what you're after since it seems you're trying to simplify the semantic image, not just the raw number of pixels.
  7. Jan 27, 2015 #6


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    It is "resolution". if you reduce the number of pixels you reduce the resolution.

  8. Jan 27, 2015 #7


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    The catch all term for images in general (including vector images) is "scaling". For scaling bitmaps (raster) the process is called "resampling", going from low resolution to high resolution is "upsampling" while going from a high resolution to a low resolution is called "downsampling".
  9. Jan 27, 2015 #8
    Thank you everyone! I think "downsampling" is it. Just to understand further, interpolating is a method for upsampling, am I right?

    I was trying to simplify an image by reducing just the raw number of pixels.
  10. Jan 28, 2015 #9


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    Staff: Mentor

    Interpolation is also needed for downsampling. For example, consider downsampling an image from 1000 x 1000 pixels to 700 x 700. If the pixels are to remain evenly distributed, the centers of most of the new pixels cannot be at the same locations as the centers of the old pixels, so they have to be interpolated from the old pixels.
  11. Jan 28, 2015 #10
    The term is downsampling " Downsampling is the process by which a high-resolution image is transformed into a lower resolution image."
  12. Jan 28, 2015 #11
    I think it's rescaling the image to a smaller size that is to transform your image from one size to another. By this, the number of pixels gets reduced.
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