[Qgis-developer] Feedback for contrast enhancement ... enhancements ?

[Andrew]

One note I would add is that the  2-click option does not work with a
singleband pseudocolor renderer(neither does the raster toolbar which
offers a 1-click stretch).  So I think updating the right-click>"Stretch
using current extent" to work with singleband pseudocolor would be
excellent to include. Also, I agree that min/max would be good as a
default, for singleband at least.  Beyond that I like the sound of solution
and I would love to see this functionality in QGIS.

a

On Fri, Sep 2, 2016 at 3:38 AM, Even Rouault <even.rouault at spatialys.com>
wrote:

> Hi,
>
> There has been interest expressed to improve the usability of the contrast
> enhancement function. Basically there are workflows where you want the
> min/max
> values used by contrast enhancement to be updated each time you pan or zoom
> the canvas. From what I've seen, here's what currently exists:
> - a long method (6 clicks): through the Style tab of the layer properties
> - a faster method (2 clicks): through the "Strech using current extent" of
> the
> contextual menu of the layer panel.
>
> When you have several rasters loaded, even the 2-click method is
> inconvenient,
> so there's a need for a 0-click solution (once the layers have been
> configured)
>
> Another shortcoming in the current implementation is that the settings of
> the
> "Load min/max values" foldable group are not persistant, which requires re-
> setting them if you're not happy with the default Cumlative count cut
> method.
> And if you use the "Strech using current extent" menu item, the genuine
> min/max values are used (not the 2-98% cumulative count cut)
>
> So I was thinking to something along the following lines:
> - make the min/max settings persistant
> - remove the "Load" button and "Clip extent to canvas" checkbox, and
> replace
> them by 3 radio buttons to determine the scope of statistics : "Whole
> raster",
> "Current canvas" and "Updated canvas". See the attached
> proposal_min_max.png.
> The function of the Load button would be replaced by the general Apply / OK
> buttons.
> - when the user manually enters the min/max values, the 2 groups of radio
> buttons (method to compute min/max and scope of statistics) would be
> unchecked
> so that is is clear that they don't come from computed statistics. I also
> think that when you select "Current canvas", once the Apply/OK buttons have
> been pushed, the checked state of Current canvas shouldn't be saved. This
> way
> when you display the layer properties you have a good idea of where the
> current min/max values come from.
> - make the "Strech using current extent" method honour the way min/max are
> computed in the min/max settings instead of using systematically the
> min/max.
> So when "Updated canvas" would be selected, it would have no (extra)
> effect as
> expected.
>
> Any opinions ?
>
> Even
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
>
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