Hi Agus ,
thx for your informations.
> Opening the raster layers very fast but getting a bad visualization
> would not be a major
> waste of time? This is what currently happens to me: the initial
> display is always useless.
>
I understand your point of view, but i guess is not a need for every
users. Same users can't wait the 4+ minutes need for the elaboration of
a raster.
Again because an user could open usually more than 20 rasters for every
session, I guess this elaboration should be absolutely optional to avoid
a really big lost of time.
> If your raster layers have similar statistics and or you want to
> display them with the same stretching so
> that grey levels or colors are comparable (which is often my case
> also, with time series of ndvi for example), a common style file would
> be the best solution.
Your solution seem good to me.
We have more set of rasters of ortophoto type colors and grey.
Eachset of colors photo is surely with comparable levels, instead I
don't know for the gray photo sets.
They are too older (1954 and so on).
Instead for raster cell (grid data) from Lidar:
Just now we begin to merge all our sets to have a full land-cover.
So we are merging 1x1, 2x2 and 3x3 meters cells.
I don't know if this could have some trouble with having a comparable
set of values, but guess of no.
Surely is not possible to find a unique style good for all the sets, but
is possible to establish a good style for each set.
>...Perhaps, in
> case a raster style is present, the by default procedure and
> calculations could be bypassed. Would this be a good solution
> in your case?
>
You mean a file raster-style in the same folder of the raster set or of
the catalog file ?
I guess this could be a good compromise to help the use in situation
like ours.
Andrea.
Il 22/04/2012 19:43, Agustin Lobo ha scritto:
Andrea,
Opening the raster layers very fast but getting a bad visualization
would not be a major
waste of time? This is what currently happens to me: the initial
display is always useless.
If your raster layers have similar statistics and or you want to
display them with the same stretching so
that grey levels or colors are comparable (which is often my case
also, with time series of ndvi for example), a common style file would
be the best solution. Perhaps, in
case a raster style is present, the by default procedure and
calculations could be bypassed. Would this be a good solution
in your case?
Agus
El día 20 de abril de 2012 15:10, Andrea Peri<aperi2...@gmail.com> escribió:
- on initial load of a raster, generate a quicklook that is the larger
of 1/4 screen resolution or 500x500 pixels by sampling every nth pixel
- generate a histogram from the quicklook
- calculate clipped 2% - 96% range min max for each band
- apply a histogram stretch based on the above
- the histogram could be used for generating the graph in raster
props, and the quicklook could be used to create thumbs and previews
etc
- ideally we should cache these quicklooks and only regenerate them if
the underlying dataset has changed
I believe if we do this we will have fast initial load and the images
(grayscale and rgb) will 'look right' when first loaded (i.e with good
contrast) and it would not be necessary to assign any color value to
grayscales by default.
Regards
Hi,
just my 2 ct.
I guess the more important capability with raster is to open they faster
possible.
I fear calculate all these values on first opened take more time than what
is waitable for the open of a raster.
Perhaps this action should be choosable by settings ?
Of course I see our situation.
Our situation is of more sets of raster (7-800 each set) where every raster
is grey level or true color of 3-400 Mbyte each.
And all these raster are accessible by a remote shared server to our users.
For a total, actually, of about 13.000 rasters.
I don't understand if this new feature could be really usable in a situation
like our.
--
-----------------
Andrea Peri
. . . . . . . . .
qwerty àèìòù
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