On 6 Aug., 18:07, John Tamplin <j...@google.com> wrote:
> When you say "good support", what exactly do you mean? I think it is not
> practical to support image bundles with transparency in the same manner as
> all the other browsers on IE6. Various approaches that I know of:
>
> 1. *bundling everything into one PNG keeping alpha*
> doesn't work in the general case due to memory requirements of the alpha
> filter, runtime cost of not using filter on IE7
> 2. *bundling everything into one GIF*
> doesn't work in the general case because you only have an 8-bit palette
> to share between all the images
> 3. *detect images with transparency and "bundle" them separately*
> works, but defeats the point of image bundles (though the user code is
> unchanged and works properly on other platforms), runtime cost for IE6/7
> permutation
> 4. *encode all transparency as single-bit alpha on IE6
> *lose antialiasing, keep extra image bundles just for IE, runtime cost
> for IE6/IE7 permutation
>
> We are currently at #1, without runtime detection of IE7. Fixing that is
> relatively easy. #2 seems a non-starter, though it could be useful for
> specific cases where palettes are small -- still since it isn't a general
> solution it doesn't seem worthwhile. #3 seems straightforward and will
> continue to work but loses the benefit of image bundles on IE6. #4,
> assuming I am remembering correctly that IE6 does support single-bit alpha
> in PNGs, seems the best compromise but the most work.
With good support I mean transparency support without consuming that
much of memory for each image.
Point 3 is what I thought of. If a user defines a GIF image as source,
we don’t bundle it for IE6/7. We just handle it as we are handling the
animated images. If the user however defines a PNG image or JPEG image
than he would have the real bundle and needs to add the filters (only
for PNG). The only change would be that if you have a GIF image it
would not be transformed and bundled for the ie6 deferred binding.
With this approach we don’t loose any quality of the original image.
We would use the real imagebundle for everything that is not a GIF
image. GIF images would be served as standalone image. But looking
into the gain you get from this (memory usage and application speed)
this is the way to go (in my opinion).
Sven Brunken
Ext GWT Core Developer
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