Fwd: ISO 12647-7
Fwd: ISO 12647-7
- Subject: Fwd: ISO 12647-7
- From: Lee Badham <email@hidden>
- Date: Mon, 21 May 2007 17:55:52 +0100
Hi,
I agree that this is the way of calculating ∆H normally, but how
could this work when measuring grey scales?
For instance,
Target Lab 50 0 0.1
Measured 50 0 -0.1
This gives a ∆H of 180 even though the 2 colours are very close
Using the ab ∆E method it gives a ∆E of 0.28. I think this is the
method used within ISO 12647-7.
On 21 May 2007, at 16:22, Fleisher, Ken wrote:
I should add the following notes (From Brude Lindbloom's site):
Implementation Notes:
1. H is in degrees, not radians.
2. If H < 0°, add 360° to it.
3. If H ≥ 360°, subtract 360° from it.
4. In computing H, be careful with the inverse tangent since a
could be
zero. Instead, use special math functions to do this. In both the
Standard C
library and Java, this function is called atan2. In Microsoft
Excel, it is
called ATAN2. These special functions will compute the proper inverse
tangents without needing to worry about "divide by zero" conditions.
Lee Badham
Bodoni Systems Ltd
www.bodoni.co.uk
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden