[Qgis-developer] blur only alpha pixels

[Larry Shaffer]

Hi Larissa,

On Wed, Oct 30, 2013 at 3:21 AM, Larissa Junek <junek at gbd-consult.de> wrote:

> Hello,
> we want to describe the Shadow menu of the labels core application in
> the user manual.
> What effects can I achieve using 'Blur only alpha pixels'? What can I
> do with this option? Does 'alpha' have to do something with
> transparency?
>

Hmm. Something's wrong with that option. It is supposed to show only those
pixels that have a partial alpha component beyond the base opaque pixels of
the component being blurred. For example, if you set the shadow of some
text to be gray and turn on that option, it should still show a duplication
of the text, colored as per the shadow color option, but with any blurred
shadow that extends beyond its text. With the option off, in this example,
it will blur all pixels of the duplicated text.

This is useful for creating a shadow that increases legibility at smaller
output sizes, e.g. like duplicating text and offsetting it a bit in
illustration programs, while still showing a bit of shadow at larger sizes.
Apparently, there is an error with re-painting the opaque pixels back over
top of the shadow (depending upon the shadow's color), when that setting is
used.

So, not sure what to do about the user guide description, since it that
option is broken right now.

If you need any help with descriptions of anything new with labeling,
please let me know.


Regards,

Larry



> Kind regards,
> Larissa
>
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