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Re: [whatwg] Adding features needed for WebGL to ImageBitmap

From: Mark Callow <callow.mark@artspark.co.jp>
Date: Thu, 18 Jul 2013 18:45:49 +0900
Message-ID: <51E7B94D.4040704@artspark.co.jp>
To: "K. Gadd" <kg@luminance.org>
Cc: whatwg@whatwg.org
On 2013/07/18 16:34, K. Gadd wrote:
>
> I understand the rationale behind gregg's suggestion for flipY, but
> ultimately don't know if that one makes any sense in a HTML5 context. It
> basically only exists because of the annoying disagreement between APIs
> like OpenGL and other APIs like HTML5 Canvas or Direct3D, specifically
> about which direction the Y axis goes. 
It exists because of the annoying disagreement between the orientation
of the data in most image file formats and the default orientation for
textures images in OpenGL. There are a some image file formats that have
a bottom left orientation and there is one, extremely common, format,
EXIF, that includes metadata giving the visual orientation of the image.
The flipY item in the proposed dictionary could be handily extended to
an enum. E.g.,

  * "none" - leave orientation alone
  * "flipY" - ignore the EXIF orientation, just flip in Y
  * "topLeftEXIF" - identify visual orientation from EXIF data and
    re-order data so top-down, left-to-right processing for display
    results in correct visual orientation
  * "bottomRightEXIF" - as above but ordered for bottom-up,
    left-to-right processing

Regards

    -Mark

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Received on Thursday, 18 July 2013 09:46:17 UTC

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