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 for progressive coding
From The Free On-line Dictionary of Computing (30 December 2018) :

  progressive coding
  interlaced image
      (Or "interlacing") An
     aspect of a graphics storage format or transmission
     algorithm that treats bitmap image data non-sequentially
     in such a way that later data adds progressively greater
     resolution to an already full-size image.  This contrasts
     with sequential coding.
     Progressive coding is useful when an image is being sent
     across a slow communications channel, such as the Internet,
     as the low-resolution image may be sufficient to allow the
     user to decide not to wait for the rest of the file to be
     In an interlaced GIF89 image, the pixels in a row are
     stored sequentially but the rows are stored in interlaced
     order, e.g. 0, 8, 4, 12, 2, 6, 8, 10, 14, 1, 3, 5, 7, 9, 11,
     13, 15.  Each vertical scan adds rows in the middle of the
     gaps left by the previous one.
     PNG interlaces both horizontally and vertically using the
     "{Adam7" method, a seven pass process named after Adam
     M. Costello.
     Interlacing is also supported by other formats.  JPEG
     supports a functionally similar concept known as Progressive
     JPEG.  [How does the algorithm differ?]
     JBIG uses progressive coding.
     See also progressive/sequential coding.
     ["Progressive Bi-level Image Compression, Revision 4.1",
     ISO/IEC JTC1/SC2/WG9, CD 11544, 1991-09-16].

Contact=webmaster@dict.org Specification=RFC 2229