[Qgis-developer] raster visualization

[Agustin Lobo]

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 <aperi2007 at 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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