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Re: [css-masking][css4-background][css-images] 9-part sliced images (was: [css4-background] 9-part slicing images in background-image)

From: Dirk Schulze <dschulze@adobe.com>
Date: Thu, 2 Jan 2014 06:40:02 +0000
To: Rik Cabanier <cabanier@gmail.com>
CC: Tab Atkins Jr. <jackalmage@gmail.com>, Jet Villegas W3C <w3c@junglecode.net>, Dean Jackson <dino@apple.com>, "liam@w3.org" <liam@w3.org>, Brad Kemper <brad.kemper@gmail.com>, www-style list <www-style@w3.org>, Simon Fraser <simon.fraser@apple.com>
Message-ID: <5C93D8CB-9CF3-4004-AEDA-2D574BB7AF70@adobe.com>
> 
> On Jan 2, 2014, at 6:15 AM, Rik Cabanier <cabanier@gmail.com> wrote:
> 
>> 
>> 
>> 
>> On Wed, Jan 1, 2014 at 7:51 AM, Dirk Schulze <dschulze@adobe.com> wrote:
>> Hi,
>> 
>> Starting to look at the image function again. IMO it makes sense to base the syntax and behavior of a sliced-image() on the ‘border-image’ shorthand[1]. (Type names shortened in this mail.)
>> 
>>         border-image: [ <image> | none ] ||  <image-slice> [ / <image-width>? [ / <image-outset>]? ]? || <image-repeat>
>> 
>> with:
>> 
>>         <image-slice> = [ <length> | <percentage> | <number> | auto ]{1,4}
>>         <image-width> = [ <length> | <percentage> | <number> | auto ]{1,4}
>>         <image-outset> = [ <length> | <number> ]{1,4}
>>         <image-repeat> = [ stretch | repeat | round | space ]{1,2}
>> 
>> The area for 'border-image' is determined by the border-box. The area can be extended with 'border-outset’. CSS Image already specifies an image area for a bunch of properties. Other properties like ‘background’ and ‘mask’ specify their own image area. I think the function shouldn’t try to mess up with these definitions and therefore I suggest to leaf <image-outset> and <image-width> out of the equation for now.
>> 
>>         sliced-image(
>>                 [ <image> | <string> ] ||  <image-slice> || <image-repeat>
>>         )
>> 
> Is there ever a reason to repeat a 9-slice image? It makes sense for border-image because it doesn't paint the center so you get repeating patterns on the outside.
> It will look funny since you'll get square patterns. Maybe this attribute could be dropped?

That is the key part of border-image and of this image function. Otherwise you can not do postage stamp effects with repeating perforations that are (nearly) independent of the element size. 

Greetings,
Dirk

>>  
>> 
>> If needed we can add  "[ / <image-width>? [ / <image-outset>]? ]?" later. The function would follow the definitions of 'border-image-*’ properties otherwise.
>> 
>> Greetings,
>> Dirk
>> 
>> [1] http://dev.w3.org/csswg/css-backgrounds-3/#border-image
>> 
>> On Dec 18, 2013, at 11:33 PM, Tab Atkins Jr. <jackalmage@gmail.com> wrote:
>> 
>> > On Wed, Dec 18, 2013 at 1:01 PM, Dirk Schulze <dschulze@adobe.com> wrote:
>> >> On Dec 18, 2013, at 9:44 PM, Tab Atkins Jr. <jackalmage@gmail.com> wrote:
>> >>> I believe that things like this should first be attempted as
>> >>> functions, and if they end up too complex (which it probably will), we
>> >>> just give up and try to add it to SVG instead.  The only problem there
>> >>> is that we don't have an easy way to embed SVG in CSS, which is a
>> >>> problem we can and should fix separately.
>> >>
>> >> I interpret your mail that you would like to see the image function before we introduce new properties (introduce in specifications since they are already there).
>> >
>> > Right.  The argument's simple; almost anything you might want to do
>> > with an image, you want to be able to do it to images everywhere.
>> > Limiting it to one context via properties (or spreading it piecemeal
>> > by adding N sets of properties one by one) is bad.
>> >
>> >> I am generally fine with that but fear that a mockup, the draft and the final implementation would take a lot longer than specifying the implementation we already have. I can be convinced though.
>> >>
>> >> We can start from what we have in 'border-image' and take a look what is needed to take over:
>> >>
>> >> * border-image-source: <image> | none
>> >>
>> >> This on is kind of obvious, we need to reference the <image>: sliced-image(<image> …)
>> >>
>> >> * border-image-slice: [<number> | <percentage>]{1,4} && fill?
>> >>
>> >> This is the important part that defines the regions to slice the image. ‘fill’ removes the middle part. I do not think that we need ‘fill’. sliced-image(<image> [<number> | <percentage>]{1,4} …)
>> >
>> > Right, removing the center is a very border-image specific thing.  If
>> > you really want to reproduce it yourself, just make the center of your
>> > image transparent.
>> >
>> >> * border-image-width
>> >>
>> >> This defines the regions in which we draw the 9 sliced image parts.
>> >>
>> >> * border-image-outset
>> >>
>> >> How much does the border image area extend the border box. Again, useful but not necessarily helpful within the image function.
>> >>
>> >> * border-image-repeat
>> >>
>> >> Shall a tile be repeated, stretched, repeated as long as it fits, repeated as long as it fits into the border image area but with equal space?
>> >>
>> >> I think it gets clear that we can represent the first two properties in the sliced-image() function. The last three are important for the actual visual output. Currently I am unsure how they can be represent in the image itself. It feels more like this needs to be done by the property using the sliced-image() function.
>> >
>> > Depends on how you're envisioning things.  Creating a 9-sliced image
>> > as an abstract thing, only the first two are necessary, and you apply
>> > the other three via some other function at time of use.  But you can
>> > also do the whole thing at once at time of use.  Depends on how much
>> > abstraction you want.  border-image suggests that you don't need to
>> > define the 9-slice as a separate thing, and it's okay to pull them all
>> > together.
>> >
>> > ~TJ
>> 
>> 
> 
Received on Thursday, 2 January 2014 06:41:04 UTC

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