[Bug 12089] New: Under 4.8.11.1.2, Transformations, the specification reads: The transformations must be performed in reverse order. For instance, if a scale transformation that doubles the width is applied, followed by a rotation transformation that rotates drawing opera

http://www.w3.org/Bugs/Public/show_bug.cgi?id=12089

           Summary: Under 4.8.11.1.2, Transformations, the specification
                    reads: The transformations must be performed in
                    reverse order. For instance, if a scale transformation
                    that doubles the width is applied, followed by a
                    rotation transformation that rotates drawing opera
           Product: HTML WG
           Version: unspecified
          Platform: Other
               URL: http://www.whatwg.org/specs/web-apps/current-work/#tra
                    nsformations
        OS/Version: other
            Status: NEW
          Severity: normal
          Priority: P3
         Component: HTML Canvas 2D Context (editor: Ian Hickson)
        AssignedTo: ian@hixie.ch
        ReportedBy: contributor@whatwg.org
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-wg-issue-tracking@w3.org,
                    public-html@w3.org


Specification:
http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html
Section:
http://www.whatwg.org/specs/web-apps/current-work/complete.html#transformations

Comment:
Under 4.8.11.1.2, Transformations, the specification reads: The
transformations must be performed in reverse order. For instance, if a scale
transformation that doubles the width is applied, followed by a rotation
transformation that rotates drawing operations by a quarter turn, and a
rectangle twice as wide as it is tall is then drawn on the canvas, the actual
result will be a square. ...  This is incorrect. Rotation and scaling are
commutative. When a rectangle is rotated a quarter turn by changing the
coordinate space, the x-axis is vertical, and scaling up the x direction will
not compress the rectangle into a square. Instead, it will make it 4x as tall
as it is wide, just as it does if you scale first, then rotate.

Posted from: 67.116.239.5

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Received on Tuesday, 15 February 2011 17:57:35 UTC