Help understanding Refine Edge using Select and Mask

[Azzam Masood]

So, below is before and after refinement using Color Aware/Object Aware (Do not know which one it is, since I'm backtracking through scriptlistener). Radius of 4 px is selected in Edge Detection, and Smart Radius, Decontamination are off.

I need to understand what exactly happened. I do not understand edge refinement at all, or how my left pixelized binary image turned into the non-binary image on the right. Help, please?

[@mj]

Hi @Azzam Masood ,

Your original image (left) looks like a 1-bit image.

Can you help us understand what your trying to do?

Are you trying to select all the black pixels for example?

Best

mj

[Azzam Masood]

Hello. I'm trying to select all white pixels, and then refine the edges is what I think is happening in the right image.

[Trevor.Dennis]

Can you show us what you are trying to select?

And explain in more detail what we are looking at in your screen shots above?

I have no more idea than mj what is going on here.

[Azzam Masood]

The image on the left is a mask. The white pixels represent the pixels where my original color will later be present. However, the binary mask on the left has to be converted into the grayscale mask on right.

[@mj]

Hi,

So the way I understand this is you've taken a mask and applied a refine edge to it?

I'm trying to work out why you'd do that. Can you help us understand?

Select and Mask is for perfecting selections.

Also, what do you mean by binary mask?

This resource might help. https://helpx.adobe.com/photoshop/using/select-mask.html

Best

mj

[D Fosse]

The principles are pretty simple, but more easily illustrated than explained.

This starts with a binary mask, either black or white.

The refine edge brush, when painted over the mask edges, maps the mask values according to the main pixel image values, giving a much more natural-looking mask. This requires a clear tonal contrast in the original image.

The others are pretty self-explaining:

Finally, you can output to a new selection, or to a layer mask.

[Azzam Masood]

So what I gather from this is that, my pixelized image on the right has all white pixels selected and refine-brushed. How does refine brush work exactly? Does it dilate the image?

[D Fosse]

I don't know how it works, but I can see what it does. It uses the image itself as basis for rebuilding the mask edge.

I honestly think the best thing you can do is play with it a bit, just to get a feel for what it does - and most importantly, where it's effective and where it's just in the way.

It doesn't always work, it's only effective on high-contrast edges. It does work with strong color contrast, but better on high tonal contrast. With poor contrast, you mainly get smearing.

Even without the refine edge brush, you still have feather, smooth, and expand/contract in the same place, with a live preview. That's way more than we had some years ago.

[Azzam Masood]

Uses the image itself for building the mask edge? Where can I go to understand this underlying algorithm? Thanks in advance.