RGB的白色不正确

Question

Check out the code

const CGFloat *c = CGColorGetComponents([[UIColor whiteColor] CGColor]); 
slider1.value = c[0];
slider2.value = c[1];
slider3.value = c[2];

c[2] is getting 0. For whiteColor all RGB values shld be 1.0. Why its not returning correct value for the blue component?

Any code snippet? for getting RGB values from white color?

Answer 1

Try CGColorGetColorSpace([[UIColor whiteColor] CGColor])

You will see it is not RGB. It has 2 components only: greyscale and alpha

Answer 2

Use this code: CGContextSetFillColorWithColor(ctx,[UIColor whiteColor].CGColor);

Works with colors and grayscale.

Answer 3

This snippet of code should work with both RGB and grayscale:

CGFloat *components = (CGFloat *) CGColorGetComponents(<UIColor instance>.CGColor);
if(CGColorGetNumberOfComponents(<UIColor instance>.CGColor) == 2)
{
  //assuming it is grayscale - copy the first value
  components[2] = components[1] = components[0];
}