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From: Vinod on 2 Mar 2010 00:42
Hello Friends,

Can you please explain what is radial gradient? A normal gradient(horizontal/vertical) is the difference between a pixel and its preceding pixel. Does this hold true for the radial gradients as well?

If so , how can one know about the presence/absence of vignetting effect in images?
Please advice me on this.

Regards,
Vinod Karuvat.
From: Walter Roberson on 2 Mar 2010 01:09
Vinod wrote:

> Can you please explain what is radial gradient? A normal
> gradient(horizontal/vertical) is the difference between a pixel and its
> preceding pixel. Does this hold true for the radial gradients as well?

The normal gradient is the difference between samples divided by the
distance between the samples. For horizontal and vertical gradients for
square pixels, the distance between the samples is 1; for pixels at
other angles, you need to calculate the distance (which will, of course,
be sqrt(2) for the pixels at 45 degree angles.)
From: Vinod on 2 Mar 2010 01:22
Walter Roberson <roberson(a)hushmail.com> wrote in message <hmia3j$gms$1(a)canopus.cc.umanitoba.ca>...
> Vinod wrote:
>
> > Can you please explain what is radial gradient? A normal
> > gradient(horizontal/vertical) is the difference between a pixel and its
> > preceding pixel. Does this hold true for the radial gradients as well?
>
> The normal gradient is the difference between samples divided by the
> distance between the samples. For horizontal and vertical gradients for
> square pixels, the distance between the samples is 1; for pixels at
> other angles, you need to calculate the distance (which will, of course,
> be sqrt(2) for the pixels at 45 degree angles.)

Hello sir,

Thank you very much indeed.

regards,
Vinod.
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