Add a switch to reverse colours and invert palette

[qgib]

Author Name: Paolo Cavallini (@pcav)
Original Redmine Issue: 9303

Redmine category:symbology

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See http://www.bc-consult.com/free/bcccoltbl1.html#i001

[qgib]

Author Name: Etienne Tourigny (@etiennesky)

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It is possible to invert the gradient in rasters (before classifying), but not in vectors. It should be easy to add a "invert" checkbox next to the color ramp selector in the Categorized and Graduated modes.

Updating the various gradient dialogs to support inverted colors would be somewhat more involved.

IMHO inverting palette is not feasible with cpt-city gradients.

[qgib]

Author Name: Etienne Tourigny (@etiennesky)

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Added invert checkbox for vector layer classification (Categorized and Graduated) in 0a8c1cc .

I am not sure that "inverting palette" is so useful (and honestly difficult or impossible for cpt-city gradients), but it could be added to the standard gradient dialog.

Leaving this open for now.

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• done_ratio was changed from 0 to 50

[qgib]

Author Name: Etienne Tourigny (@etiennesky)

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Actually, implementing "invert palette" shouldn't be too hard.

The question is, where should this option appear? In the gradient dialog boxes, or in the raster/vector classification UIs (as is done for "invert colors")?

Another question is: is this really necessary?

Here is the relevant code in the 1-band raster colour table plugin (bcccoltbl), in file Palette.py, that does the inversions.

    # interfaces to export useful objects
    def getColPalette(self, bInvert = False, bReverse = False):
        """
        -- return the colour palette array
        """
        if bInvert:
            #invert the colour palette
            for i in range(self.nColo+1):
                self.arColo[i,0] = 255 - self.arColo[i,0]
                self.arColo[i,1] = 255 - self.arColo[i,1]
                self.arColo[i,2] = 255 - self.arColo[i,2]
        if bReverse:
            #reverse the colours order
            ar = np.zeros((self.nColo+1,4),int)
            n = self.nColo
            for i in range(self.nColo+1):
                ar[i,0] = self.arColo[n -i,0]
                ar[i,1] = self.arColo[n -i,1]
                ar[i,2] = self.arColo[n -i,2]
            self.arColo = ar
        return self.arColo

[qgib]

Author Name: Etienne Tourigny (@etiennesky)

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Added a few people to this ticket, would appreciate feddback on questions raised in last comment.

[qgib]

Author Name: Paolo Cavallini (@pcav)

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Not sure it is necessary. I'd put it besides the "invert colour" checkbox.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• easy_fix was configured as 0

[qgib]

Author Name: Paolo Cavallini (@pcav)

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Implemented

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• resolution was changed from to fixed/implemented
• status_id was changed from Open to Closed