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Re: Async Image -> ImageData conversion

From: Boris Zbarsky <bzbarsky@mit.edu>
Date: Wed, 24 Jun 2015 11:12:22 -0700
Message-ID: <558AF306.2060804@mit.edu>
To: public-webapps@w3.org, Jeff Muizelaar <jrmuizel@mozilla.com>
On 6/19/15 5:43 AM, Ashley Gullen wrote:
> I've not done this before, so I've no idea if this is the right/useful
> approach, but I drafted a spec for it here:
> https://www.scirra.com/labs/specs/imagedata-blob-extensions.html


We at Mozilla were just discussing this proposal, and we have a concern.

With this proposal, going from an <img> to an ImageData requires 
conversion of an intermediate ImageBitmap.  Unfortunately, an 
ImageBitmap is specified to be paintable "without undue latency", which 
we interpret to mean it needs to have decoded image data, and the 
ImageData will end up needing to copy said data in practice (because it 
needs an editable copy).

That creates two copies of the decoded image data in memory, which seems 
fairly undesirable on memory-constrained devices.

Received on Wednesday, 24 June 2015 18:12:53 UTC

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