[Qgis-user] Vector area calculation

[Fred Lali]

Members, I need help or guidance on how to calculate the polygon area, may be  I'm doing is a wrong way.

I toggle edit tab i.e the pencil icon and i use vectors geometry tools to export/add geometry columns. But it gives me area as a decimal 



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-----Original Message-----
From: "Benoît Laurent" <blaurent at heurisis.eu>
Sent: ‎23/‎06/‎2015 12:05
To: "qgis-user at lists.osgeo.org" <qgis-user at lists.osgeo.org>
Subject: Re: [Qgis-user] Transparency for vector symbol layers

Hello Andreas,

Thank you very much for your complete answer.

Actually, I reached my goal using rule based renderers.

Regards,

Benoît


Hi Benoit, 

It depends. Yes - you can mix transparent and opaque features. For each color you can also set the opacity/transparency value. 

However, if two features overlap and you use transparency on the feature level, you can see the features shine through - whereas when the transparency would be on the symbol level (which isn't implemented yet in QGIS) you would first composite all elements in a symbol level and then apply the opacity on the whole group. See http://www.w3.org/TR/2011/REC-SVG11-20110816/masking.html#ObjectAndGroupOpacityProperties for the difference. In http://www.w3.org/TR/2011/REC-SVG11-20110816/images/masking/opacity01.png - if you look at the bottom row of circles - the second pair of circles has the opacity on the group of two circles, whereas the third pair has opacity on every single element. I hope you can see the difference. 

It would be very cool if QGIS could have a more fine-grained opacity - new opacity on symbol level and new opacity on a whole group of layers. It would make the cartographic options even better ;-) 

Andreas 

On 19.06.2015 16:40, Benoît Laurent wrote: 

Hello, 

I noticed this feature request : https://hub.qgis.org/issues/3438. 

Is it possible to have semi-transparent and opaque features within the same layer ? 

Best regards, 

Benoît 

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