[mythtv-theming] How would I create a vignette effect with fanart?

[David Asher]

On Sep 24, 2009, at 10:04 AM, Robert McNamara wrote:

> On Thu, Sep 24, 2009 at 4:48 AM, David Asher <asherml at gmail.com>  
> wrote:
>> I'm interested in creating a similar effect as the vignette version  
>> of the
>> fanart on thetvdb.com (e.g.
>> http://thetvdb.com/banners/fanart/vignette/73739-34.jpg).  It seems  
>> like the
>> best idea, however, is to download the full sized fanart and then  
>> use MythUI
>> to create the vignette.  That way the theme can decide whether and  
>> what type
>> of vignette to use.
>>
>> Could it be done just with a single imagetype using a mask file?   
>> Or is a
>> mask file only useful for cropping?  The mask attribute description  
>> is:
>>
>> mask allows a second image to be set to alpha-mask the original.  
>> This is a
>> black and transparent image of identical size to the imagetype  
>> area, where
>> black is visible and transparent will be masked. This allows for  
>> smooth
>> edges and exotic shapes to your image. Masks cannot be resized or  
>> scaled.
>>
>> The usage of "alpha-mask" implies I could get varying level of  
>> transparancy,
>> but the later portion of the description seems to imply only black  
>> and
>> transparent are relevant.
>
> Why not just try it?
>
> Yes, a mask will work fine for your purposes.

Because I like to overthink things...

I guess I also don't understand image transparency.  In my head black  
is a color, transparent is an alpha level.  I guess my real question  
is: what attribute in the mask image implies 50% transparency?  A 50%  
gray pixel?  Something else?  Does the wiki mean opaque is visible?