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<br><br>> Date: Mon, 19 Jul 2010 14:33:01 -0700<br>> From: david@davidflanagan.com<br>> To: bzbarsky@MIT.EDU<br>> CC: whatwg@lists.whatwg.org<br>> Subject: Re: [whatwg] Canvas transform() and matrix element notation<br>> <br>> Boris Zbarsky wrote:<br>> > On 7/19/10 4:13 PM, David Flanagan wrote:<br>> >> The spec describes the transform() method as follows:<br>> >><br>> >>> The transform(m11, m12, m21, m22, dx, dy) method must multiply the<br>> >>> current transformation matrix with the matrix described by:<br>> >>><br>> >>> m11 m21 dx<br>> >>> m12 m22 dy<br>> >>> 0 0 1<br>> >><br>> >> The first number in these argument names is the column number and the<br>> >> second is the row number.<br>> > <br>> > I agree that this is somewhat weird at first glance, but it seems to be <br>> > not uncommon for graphics libraries. For example, for cairo the call<br>> > <br>> > cairo_matrix_init(m, a, b, c, d, e, f);<br>> > <br>> > creates a matrix which represents the affine transformation [1]:<br>> > <br>> > x_new = a*x + c*y + e;<br>> > y_new = b*x + d*y + f;<br>> > <br>> <br>> Thanks for checking this; it is nice to know that there is precedent for <br>> the argument order. Changing the argument names to remove the numbers <br>> from them would make the spec less confusing. Or at least changing the <br>> argument names so that they use (standard?) row,column indexing instead <br>> of column,row indexing.<br>> <br>> David<br><div><br></div><div>But I think the number can indicate the position of the value in the matrix,</div><div>if change them into "a,b,c..." like cairo, I think it will still confuse the beginner.</div> <br><hr>Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. <a href="https://signup.live.com/signup.aspx?id=60969">Sign up now.</a> <br /><hr />Hotmail: Free, trusted and rich email service. <a href='https://signup.live.com/signup.aspx?id=60969' target='_new'>Get it now.</a></body>
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