colorsys: RGB to YIQ transform matrix

[Edward C. Jones]

In colorsys.rgb_to _yiq, the matrix of the linear transformation used is

.30 .59 .11
.60 -.28 -.32
.21 -.52 .31

The places I checked on the Internet use

.299 .587 .114
.596 -.275 -.321
.2.1 -.523 .311

Why does colorsys use a 2 decimal place wersion of the array? What is
the actual definition of the RGB to YIQ transform?

[David Berry]

Re: colorsys: RGB to YIQ transform matrix

Edward C. Jones wrote:[color=blue]
> In colorsys.rgb_to _yiq, the matrix of the linear transformation used is
>
> .30 .59 .11
> .60 -.28 -.32
> .21 -.52 .31
>
> The places I checked on the Internet use
>
> .299 .587 .114
> .596 -.275 -.321
> .2.1 -.523 .311
>
> Why does colorsys use a 2 decimal place wersion of the array?[/color]

Pass
[color=blue]
> What is
> the actual definition of the RGB to YIQ transform?[/color]

A good place to start is here,

http://www.poynton.com/ColorFAQ.html

which used to contains details of RGB->YIQ and much much more on color
space transforms.

Dave

[A.M. Kuchling]

Re: colorsys: RGB to YIQ transform matrix

On Mon, 10 Nov 2003 22:53:58 -0500,
Edward C. Jones <edcjones@erols .com> wrote:[color=blue]
> Why does colorsys use a 2 decimal place wersion of the array? What is
> the actual definition of the RGB to YIQ transform?[/color]

I'll wager there's no technical reason. Maybe whoever wrote the module
used a reference that only quoted the matrix to two places. You could submit
a patch on SourceForge to correct this.

(Hm, looks like there's no test suite for the module. That would be worth
fixing.)

--amk