Question About Co-Occurrence Grey Level Quantization

Prev Go to previous topic

Go to next topic

Last Post 22 Jul 2016 09:33 AM by anon

1 Replies

Sort:


You are not authorized to post a reply.

Author

Messages

anon

New Member

Posts:

22 Jul 2016 09:33 AM
Hi, I'm using ENVI 5.3 to run grey level co-occurrence texture analyses on a series of LiDAR-derived canopy height models. I have a question regarding the "Grey Level Quantization Levels" feature of the ENVI co-occurrence tool: Do the grey level quantization levels represent a limit in the number of values being considered by the matrix? I ask because I'm working with a collection of 8-bit rasters with values ranging from 0-63. With an 8-bit pixel depth, my data represents just 63 of 256 possible values, and so my co-occurrence matrices are filled with a large number of 0's which I've read can mess up the calculation. Limiting the data to 64 possible values would be perfect, but I'm not sure that this is what the quantization feature does. Any helps is HIGHLY appreciated! Best, Jamie Ervin

MariM

Veteran Member

Posts:2396
Veteran Member

25 Jul 2016 12:03 PM
Quantization is just constraining the range of values. From the help: G_LEVELS Use this keyword to set gray scale quantization levels, thereby reducing the number of shades of gray required to represent the image (which also reduces processing time). Set G_LEVELS to an integer scalar less than or equal to 256. This value must be a power of two. If you do not set G_LEVELS, then no gray scale quantization will be performed. So if you only have 64 actual values in your data, then a quantization would make sense and reduce the values down to those that fall within the min/max of the data range.

You are not authorized to post a reply.