"Mike Russell" wrote in message
"Des" wrote in message
Hello
Does anyone know of an algorithm which will accurately convert an acv
file
to a look-up-table?
Reading an acv file is no problem - it's just a sequence of 2D points
for
each curve.
But I'm having big problems converting the points to the same curve as PhotoShop. I can get close - but not spot on.
Many thanks for any input or pointers.
Curve a gradient and save it as a raw file. Create an action to do this
if
you have multiple curves to convert.
Splines should do a good job of duplicating the curve mathematically.
What
function are you using, and what is the nature of the errors you are encountering?
--
Thanks for the response.
The PS curve is defined entirely by the input points (ie the points written to or read from the acv file).
In addition the curve is not changed if you add another point that is already on the curve - which is intuitively expected.
Taken together this means that the curve must maximise/minimise some global property.
I've initially assumed that the curve is a minimum curvature curve.
I tried fitting a cubic bezier spline to the points with the control points set to minimise curvature (which is equivalent to ensuring curvature continuity for a cubic spline - ie a b-spline).
My results look good in terms of curvature, but are different from the curve PS generates. The PS curve looks too loose to me. I was wondering if anyone knew what sort of curve is being fitted - maybe they use a higher order spline?
Thanks again
Des