python set_source_rgb set_source_rgba values

arizonagroovejet · 07-04-2010, 01:41 PM

I've recently starting dabbling with python and gtk/cairo bindings. Can anyone point me to a quick and easy way to convert a colour value from hex (e.g. #FF8000) into the format required by the set_source_rgb function?

E.g. I have this:

Code:

        cr=area.window.cairo_create()
        cr.set_source_rgba(0.5,0.5,0,0.8)
        cr.rectangle(100,100, 100, 100)
        cr.fill()

but I want to specify the colour #FF8000. I can easily get an rgb value for that hex number using Gimp, but that's with values between 0 and 255 and set_source_rgba wants values between 0 and 1. So I have to bring up a calculator and divide the values Gimp gives me by something or other to get the values that set_source_rgba wants

Having to keep converting colours by such a method is very tedious. I'm thinking there must be a better way, but I've no idea what it is.

Sergei Steshenko · 07-04-2010, 02:41 PM

Quote:

Originally Posted by arizonagroovejet

...So I have to bring up a calculator and divide the values Gimp gives me by something or other to get the values that set_source_rgba wants ...

Huh ?

Python is a programming language, so why wouldn't you perform the division in it ?

arizonagroovejet · 07-05-2010, 02:18 PM

Quote:

Originally Posted by Sergei Steshenko

Python is a programming language, so why wouldn't you perform the division in it ?

Well yeah I could, obviously. But I was wondering whether there was any sort of online conversion tool or something around that would save me the (admittedly minor) effort of writing some code. Or maybe some way the functions accept hex values.

bgeddy · 07-05-2010, 03:55 PM

Here's a little module with a function named split_col that takes a 24bit colour value and returns a tuple of three values with the MSB first (highest first). So the hex value 0xFFFFFF would return (1.0,1.0,1.0). I've assumed the conversion works simply like this. Just import this and call it with your original hex string of #FF8000 like this:

Code:

rgb_col=split_col(0xff8800)

and a tuple of the three colours is returned. Here's the module:

Code:

def split_col(full):
    """  split_col(full=24 bit color value) return tuple of three colour values being 0-1.
         Assume 0xFFFFFF=White=(1,1,1) 0x000000=Black=(0,0,0) """
    return ((full >> 16)/255.0,(255 & (full >> 8))/255.0,(255 & full)/255.0)

Hope it's useful.