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Thanks for clarifying. We always have to answer claims such as: "...but Arc* does like this...". We noticed the problem when compositing Landsat tiles in an area with very uniform landscape. The slight shift in RGB values with the default level=32 led to many adjacent pixels getting the same color value, and the result looked very "blocky". On 30-Jan-15 2:33 PM, Glynn Clements
wrote:
Markus Metz wrote:On Wed, Jan 28, 2015 at 10:34 PM, Micha Silver <[email protected]> wrote:When I use r.composite to create, i.e., a false_color composite from three Landsat bands, the RGB values in the composite are slightly different than the values in the original bands. Why is that?Because the number of levels to be used for each component is by default 32, not 256 [0].You can use levels=256 if you want 256 levels. But the resulting map will have a very large colour table (65536 rules), which will negatively affect the performance of anything which reads the colour table. Which is why the default is 32 levels rather than 256. -- Moshav Idan D.N. Arava, 86840 cell: 0523-665918 http://www.surfaces.co.il |
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