[QGIS-Developer] QGIS Georeferencer improvements

[Frank Sokolic]

Hi Martin,

On 2020/04/01 11:48, Martin Dobias wrote:
> Hi Frank
>
> On Wed, Apr 1, 2020 at 8:47 AM Frank Sokolic <sokolic at worldonline.co.za> wrote:
>>> B. map coordinates - that is what ArcGIS does. The image is placed at
>>> some initial position in the map, picking of image coordinates and map
>>> coordinates for GCPs is done in the same map canvas. (i.e. two clicks
>>> in single map canvas)
>>>
>>> The option B has the advantage that it is quite easy/intuitive to have
>>> live preview of the image transformation as GCPs are being added. With
>>> option A the live preview of the transform is not really possible (we
>>> are still in image coordinates) - and the preview would need to be in
>>> a separate map canvas.
>> While I like the live preview of option B, I find this option difficult
>> to use when georeferencing the raw image against a raster dataset such
>> as an aerial photograph. The top raster in the drawing order, e.g. the
>> raw image, covers the bottom raster as the live image transformation
>> proceeds, requiring the top raster to be toggled on/off when identifying
>> GCPs. In this case I find the current dual window approach is better as
>> the images can be placed side-by-side for easier identification of GCPs.
> Yeah this case when georeferencing aerial imagery on top of other
> aerial imagery is a valid concern. This could be possibly addressed by
> having a switch (with a keyboard shortcut) that would toggle opacity
> of the georeferenced layer to 0% and 100% (or some other values).
>
> Another option would be to have an action to open a new map canvas
> dock widget containing just the georeferenced layer (with live warp as
> well) that could be either docked on the side of QGIS main window or
> even moved to a second display. Closing this map canvas dock widget
> would make the georeferenced layer appear again in the main map
> canvas...
>
> What do you think? In this way, with single canvas by default and with
> optional "pop out" georeferencing canvas we could probably address the
> issue nicely.

I like the option of a switch and keyboard shortcut. I think that 
programmatically it would be much easier to implement than having a dock 
widget. It is currently possible to assign shortcuts to the *Show 
Selected Layers* and *Hide Selected Layers* commands but these have to 
be different key combinations. It would be nice to have the same 
shortcut toggling the selected layer on/off.

> Regads
> Martin

Frank.