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Re: [css-shapes] shape-image-threshold should be clearer about >= vs >

From: Alan Stearns <stearns@adobe.com>
Date: Thu, 12 Sep 2013 08:17:51 -0700
To: Brad Kemper <brad.kemper@gmail.com>
CC: "L. David Baron" <dbaron@dbaron.org>, "www-style@w3.org" <www-style@w3.org>
Message-ID: <CE57A4BA.3E57E%stearns@adobe.com>
On 9/12/13 4:45 PM, "Brad Kemper" <brad.kemper@gmail.com> wrote:

>On Sep 11, 2013, at 2:23 PM, Alan Stearns <stearns@adobe.com> wrote:
>
>>snip
>
>> I still believe that > 0.0 is the correct
>> initial value.
>
>Well, from my perspective, >0.0 is almost always going to be wrong, and
>either require an authored value or just be off (acceptably worse, for
>many). I can't really think of many situations where >0.5 (or >=0.5)
>would not be visually better.

I'd like to get a few more people's opinions. I'm not yet convinced.

> 
>
>For high contrast image shapes, the theoretical shape edge is right in
>the middle of the anti-aliasing. Granted, that's only going to be a
>difference of maybe a pixel, but still. THAT is the real edge of the
>shape. If you rendered a vector image in a raster paint app, that is
>where the edge would be, and your >0.0 edge would be further out than the
>vector's edge. 

But that further edge ensures that the content wrapping around the image
does not collide with any of the image's rendered pixels. In most cases
you'd want even more distance than that, and would add some shape-margin
to get a bit more white space involved. I don't see the point of pulling
the content into the anti-aliased pixels.

>If the image is an SVG, don't you use the middle of the vector paths to
>determine the shape, or do you render it first and then get a shape that
>is completely outside those paths?

For a shape-outside URL that points to an SVG image, It would be the
rendering that determines the shape.

>
>For a fuzzier edge image (say, a picture of a smoke puff), I would most
>likely want my wrapping text to overlap some of the more translucent
>pixels, not being so far away that the wrapping area isn't even
>recognizable as being the same general shape. For shape-inside, I'd want
>a usable amount of space for the text. A 0.5 default would be much more
>likely to be useful in both cases.

I disagree - I think that content should by default avoid any rendered
pixels of the image. If you do want to move the content in to overlap some
of the translucent pixels, that's what the threshold property is for.

Thanks,

Alan

> 
Received on Thursday, 12 September 2013 15:18:21 UTC

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