Get Pixel Value from Layer Parameter and Arbitrary XY Coordinates

[Matt Tillman]

So this is driving me crazy. I've searched the forums and found a few promising leads, but nothing seems to work.

I am inside a float iterator for the current layer (suites.IterateFloatSuite1()->iterate_origin()).

I have passed my layer parameter into it, as a PF_LayerDef.

How do I get a pixel value from it?

What I want to do is something like this:

out =  getPixelValue(id->layer.data, xCoord, yCoord);

Am I simply approaching this in the wrong way?

Any help would be amazingly appreciated.

Thanks.

[shachar carmi]

you need to use PF_CHECKOUT_PARAM() or checkout_layer_pixels() to get an

PF_EffectWorld filled with pixels.

only then will your plug-in get the actual pixels of the layer.

now that you have it, you can use effectWorld->data as a pointer to the

first pixel and effectWorld->rowbytes to get to the address of the pixel

you want.

[Matt Tillman]

Thanks Shachar,

I've got the layer checked out, and have access to data and rowbytes. I'm just not certain of how to actually extract a pixel out of it.

Using "data"; how do I get a PF_PixelFloat out of a PF_PixelPtr? Also, what would the use in returning the first pixel?

And with regards to "rowbytes", what would an example of using that look like?

As an example, say I wanted the pixel at [10,10] in the layer?

I'm assuming it's not as simple as rowbytes[10,10] or rowbytes[width*10+10].

[françois leroy · Accepted solution]

Hi,

if you go the suites way, you can try PF_SAMPLINGSUITE and subpixel_sample.

The manual way would be:

PF_PixelFloat getPixel(PF_EffectWorld* inputP, const A_long x, const A_long y) {

  return = *((PF_PixelFloat *)((char*)inputP->data + (y * inputP->rowbytes) + x * sizeof(PF_PixelFloat )));

}

so with a pixel at [10,10], you'll get:

*((PF_PixelFloat *)((char*)inputP->data + (10 * inputP->rowbytes) + 10 * sizeof(PF_PixelFloat )));

}

Cheers,

François

[Matt Tillman]

Thanks so much for that Francois. That looks like exactly the explanation I was looking for.

[françois leroy]

Well, I got it from Toby 😉

[Matt Tillman]

Hey again.

I tried your function out, but replacing PF_EffectWorld with PF_LayerDef, as that is what my PF_CHECKOUT_PARAM() returns.

However in trying this:

PF_PixelFloat testPixel = getPixel(id->layer, 10, 10);

I get the following error:

No suitable conversion function from PF_LayerDef to PF_LayerDef* exists.

I tried removing the star from the function, but that throws more errors, saying that it needs to be a pointer type.

Sorry if this is a dumb question. I really don't know the fundamentals of C++ (I'll have to fix that). I've only ever really used C#, python and extendscript.

[françois leroy]

instead of removing the star* from the function, you should add & when you use it, like this:

PF_PixelFloat testPixel = getPixel(     &id->layer, 10, 10);

Cheers,

François

[Matt Tillman]

You're amazing! Thanks again.

It's working perfectly.

After I had a few crashes and realised I needed to check that the layer wasn't null, and that the coordinates were valid haha.

Studying up on pointers and references now