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Fwd: transparent png images

From: Wilhelm Joys Andersen <wilhelmja@opera.com>
Date: Wed, 09 Apr 2008 13:49:41 +0200
To: public-mwts@w3.org
Message-ID: <op.t9cdr7nim3w6te@kugalskapet>


I have also added a proposed new transparent PNG test:

------- Forwarded message -------
From: Tarquin (Mark) Wilton-Jones
Subject: transparent png images

Attached drop-in replacements for the images used in the transparent PNG

As well as testing the same thing as the originals in the top half of the
images, in the bottom half, they also make sure the browser uses real
alpha transparency, not simulating it by treating alpha as binary
transparency based on a certain threshold (netfront is an example, even
though it would pass the original).

They do this by layering rgb(0,1,0) with rgba(0,255,0,0.5) to produce

I tried to preserve the important PNG data chunks to make sure it still
picks up bugs in IE 6, for example. Depending on the browser's
implementation, it could show a variety of different colours:

* almost black (threshold of < 50% treated as binary transparent)
* lime (threshold of > 50% treated as binary opaque)
* blood red (bKGD chunk showing through - IE 6)
* perfect 128 green (correct support)

Unfortunately, since the passing colour is pure green, I can't make any
funny mixes, so you're stuck with lime being failure - this contradicts
normal testcases, but since the other squares are are all a very different
shade of green, it should be an obvious fail.

Wilhelm Joys Andersen
Core QA, Opera Software
Received on Wednesday, 9 April 2008 11:50:50 UTC

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