CssParameter for stroke-opacity ignored in PolygonSymbolizer

[mapserver-bot]

Reporter: myOpenLayersUName
Date: 2011/12/21 - 18:59
Trac URL: http://trac.osgeo.org/mapserver/ticket/4132
The following value is ignored in an SLD 's Stroke tag:[[BR]]
stroke-opacity

As far as I can tell, the reason is because mapogcsld.c's msSLDParseStroke method uses the following line to set this value in the style:

psStyle->color.alpha = (int)(atof(psCssParam->psChild->psNext->pszValue)*255);

While that line works for LineSymbolizer's it should be as follows for PolygonSymbolizer's:

psStyle->outlinecolor.alpha = (int)(atof(psCssParam->psChild->psNext->pszValue)*255);

Unfortunately, I don't know how I would know which Symbolizer I'm dealing with at that point in the code so I can't suggest a fix but I'm sure someone who knows this code would be able to come up with something fairly quickly.

[mapserver-bot]

Author: myOpenLayersUName
Date: 2011/12/22 - 19:02
Well, this probably isn't the proper way to do this, but I've simply put both lines of code into the block that sets the stroke-opacity in msSLDParseStroke and it works for both LineSymbolizer and PolygonSymbolizer now:

    :

    else if (strcasecmp(psStrkName, "stroke-opacity") == 0)
    {
        if(psCssParam->psChild &&  psCssParam->psChild->psNext &&
           psCssParam->psChild->psNext->pszValue)
        {
            psStyle->color.alpha =
                (int)(atof(psCssParam->psChild->psNext->pszValue)*255);
            psStyle->outlinecolor.alpha =
                (int)(atof(psCssParam->psChild->psNext->pszValue)*255);
        }
     }

     :

It's what we're going with unless I learn it's a bad idea through this venue at some point.

[mapserver-bot]

Author: dmorissette
Date: 2011/12/23 - 20:58
The title says 'stroke-opacity' is ignored, but then the rest of the comments relate to the alpha only.

Perhaps if you could include an example (SLD) that would help understand the issue?

[mapserver-bot]

Author: myOpenLayersUName
Date: 2011/12/24 - 04:47

<StyledLayerDescriptor xmlns="http://www.opengis.net/sld" version="1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/sld http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd">
    <NamedLayer>
        <Name>Polygon</Name>
        <UserStyle>
            <FeatureTypeStyle>
                <Rule>
                    <Name>Polygon</Name>
                    <Title>Drawing layer</Title>
                    <PolygonSymbolizer>
                        <Fill>
                            <CssParameter name="fill">#FF0000</CssParameter>
                            <CssParameter name="fill-opacity">0.4</CssParameter>
                        </Fill>
                        <Stroke>
                            <CssParameter name="stroke">#000000</CssParameter>
                            <CssParameter name="stroke-opacity">0.6</CssParameter>
                            <CssParameter name="stroke-width">10.0</CssParameter>
                            <CssParameter name="stroke-dasharray" />
                        </Stroke>
                    </PolygonSymbolizer>
                </Rule>
            </FeatureTypeStyle>
        </UserStyle>
    </NamedLayer>
</StyledLayerDescriptor>

This was the PolygonSymbolizer I was trying to use. Everything was rendered appropriately except the stroke-opacity. When I changed the lines as indicated above, it worked but I really have little idea whether it's correct or appropriate.

Additional background info can be found at: http://osgeo-org.1803224.n2.nabble.com/Some-PointSymbolizer-values-are-being-ignored-SLD-Syntax-problem-td7028772.html. The original message discusses stoke-opacity with PointSymbolizers (among other things), but the second and latter messages talk about stoke-opacity in the PolygonSymbolizer.

[myGitHubUName]

In direct response to dmorrisette's comment: "The title says 'stroke-opacity' is ignored, but then the rest of the comments relate to the alpha only.", the existing code seemed to look at the alpha to determine opacity elsewhere so I merely continued the practice in my code to be consistent. I thought it odd as well, but it seems to be the case throughout this particular class definition (mapogcsld).

Cheers,
jtm

[tbonfort]

msSLDParseStroke has a parameter to tell if we should use the style's color or outlinecolor. Untested fix committed, keeping fingers crossed :)