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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