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I like also the gvsig way, that uses for outlines a darker color of the same tone used for fill the polygon. This gives better results than using the black outlines. See attached image.

A workaround that meets my original desire of matching color is to eliminate the border before classifying the items. By editing the symbol and setting the border style to no pen prior to classifying will achieve this result. This does not do what lutra described.

@Médéric

Before you spend too much time coding this, can you please file a QEP over at https://github.com/qgis/QGIS-Enhancement-Proposals/issues describing your proposed approach? There's some usability issues which may result from this which I think warrant further discussion (eg, I think before implementing this we would need a way of "locking" the outline color, for cases where users do NOT want the outline colour modified. Currently there's a method for locking the fill colour for symbol layers, but not additional colours such as the outline colour. I think this needs to be addressed as a prerequisite/companion to this work).

In answer to the question though:

Médéric RIBREUX wrote:

For the moment, this feature is used only when you open a new polygon layer and when you have no default style (or no default project style). Once the layer is loaded, you can change the renderer (categories or graduated) but when you use a color ramp, only the fill color will change, not the outline color (which will be the initial random color for the simple fill renderer but darker, not black anymore).

Should I go further and try to implement automatic outline color ramps or something like that (probably much more difficult) or should the above behavior be considered sufficient to close this feature request ?

No, that wouldn't address the feature request at all.

Nyall Dawson wrote:

@Médéric

Before you spend too much time coding this, can you please file a QEP over at https://github.com/qgis/QGIS-Enhancement-Proposals/issues describing your proposed approach? There's some usability issues which may result from this which I think warrant further discussion (eg, I think before implementing this we would need a way of "locking" the outline color, for cases where users do NOT want the outline colour modified. Currently there's a method for locking the fill colour for symbol layers, but not additional colours such as the outline colour. I think this needs to be addressed as a prerequisite/companion to this work).

Hello,

I am sorry but I don't have the strength to make a QEP for this (and not enough knowledge in QGIS base code and "administrative procedure"). But I can share what I've found so far...

In file src/core/symbology-ng/qgssymbolv2.cpp:

• The default random style is in method QgsSymbolV2::defaultSymbol.
• Random color is chosen like this: QColor::fromHsv( qrand() % 360, 64 + qrand() % 192, 128 + qrand() % 128 ).
• This random color is not too bright (64 min of saturation) and not too dark (128 minimum of value).
• For polygons layers, the color is set on a QgsFillSymbolV2 which means that the color is set at the upper level of the symbol. It only affects the FillColor, not the outline one.
• To define a darker outline color, I've found that you need to add a little bit of saturation (about 50 on a scale of 0 to 254) in order to have a brighter color and to remove a greater amount of value (about 77 on a scale of 0 to 254) in order to have something darker. This is a very simple method to define the outline color but perhaps something better exists (perhaps more complex).
• The defined above Outline color needs to be applied on the first layer of the QgsFillSymbolV2 with the setOutlineColor method.