Re: Core Image in FxPlug example
Re: Core Image in FxPlug example
- Subject: Re: Core Image in FxPlug example
- From: Patrick Sheffield <email@hidden>
- Date: Tue, 28 Apr 2009 09:53:59 -0700
So - it requires 4 pixels to determine which direction to shift each
pixel? How can that work? Does it scan starting at the upper left and
take the pixel and its right most and then the two pixels below it to
determine where to move the first pixel? and how could I even build
such a buffer, since the value that was subtracted to determine the
first pixel's displacement is being subtracted FROM to determine the
second pixel. And what happens at the right/bottom edges?
Seems FRIGHTFULLY inefficient... why not use the RGBA values for this?
I am confused,
Patrick
On Apr 28, 2009, at 9:01 AM, Darrin Cardani wrote:
Glad it helps! It looks to me like Displacement Distortion is using
the magnitude and direction of edges in the map image to offset
pixels in the source image. I believe it first converts the map
image to grayscale, then finds the difference of each pixel with its
neighbors in the x and y directions. It multiplies the x and y
differences by the scale parameter and uses the resulting vector as
an offset from the current pixel in the source image.
So let's say the grayscale version of your map image looked like this:
0.75 0.89
0.23 0.52
It takes (0.75 - 0.89) = -0.14 as the x offset
It takes (0.75 - 0.23) = .52 as the y offset
It then multiplies those values by the scale parameter. Let's say
it's set to 25, so it comes up with an offset of (-3.5, 13). It adds
that to the current (x,y) coordinate and samples the input image at
(x - 3.5, y + 13).
Does that make sense?
Darrin
On Apr 27, 2009, at 5:53 PM, Patrick Sheffield wrote:
Thank you Darrin - this helps a lot.
I wonder if you could shed some light on a specific CoreImage
filter - specifically DisplacementDistortion...
In Shake and in FxScript, the X-Displacement is governed by one
channel in the displace image and the Y-Displacement by another. I
can't find any documentation on the CI filter as to how it handles
this.
Thanks,
Patrick
--
Darrin Cardani
email@hidden
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