On Oct 4, 2008, at 2:53 PM, Maciej Stachowiak wrote:
setFillColor avoid the need for allocation entirely in all cases.
We could also consider letting fillStyle take a number to be
interpreted as a 32-bit RGBA value, since modern JS engines can do
math and masking faster than string operations or array allocation.
But the broken out setFillStyle version seems like it might still be
more of a perf win in many cases.
It's worth recalling that existing content (and i imagine most complex
canvas code in general) that uses any single data structure for colour
uses arrays so that there isn't any additional allocation. The reason
you see
fillStyle = "rgba("+r+","...
is because it is much easier to work with colours when keeping the
channels as float values in [0..1], so these have to be converted to
[0..255] values for the string which is cleaner when done over
multiple lines -- eg
r = Math.round(colour[0] * 255);
g = Math.round(colour[1] * 255);
b = Math.round(colour[2] * 255);
fillStyle = "rgba("+r+","+g+","+b+","+colour[3]+")" // I have actually
seen people do "rgba("+[r,g,b,colour[3]].join()+")"; because even that
is more concise
setFillColor requires
setFillColor(color[0], color[1], color[2], color[3]);
which is still more verbose then
fillStyle = color
On Oct 4, 2008, at 8:02 AM, Kristof Zelechovski wrote:
Instead of an array, we could also use a generic, "duck-typed"
javascript object:
fillStyle = {r:0, g:0.3, b: 0.6, a:1.0};
This would seem a little clearer semantically, I think, since arrays
are after all supposed to represent a list of semantically identical
values.
The issue with this is that it doesn't make things much better than
they currently are -- you end up having to convert from arrays to an
object with named properties. While this is nice on a conceptual
level, it is far easier to work with colours if you just treat them as
vectors -- by giving each channel a separately named property you
can't trivially iterate through the channels which means you end up
having to repeat code, and also make it impossible to just do all
computation cleanly with "vectors", as you will eventually have to
convert to the object form for assignment.
--Oliver
