I've been trying to do this for a few days now and have not gotten the results I need. I'm not sure I'm using the correct terminology in the title, if not, please feel free to correct me, and I'll update it.
I want to go from this:
to this (i've sampled an area of the transparency to show the k value in case that helps). Notice the shadows/highlights are there, but nothing else:
This allows me to place a layer filled with a solid color below the transparent image. The result is a different color shirt, and shadows/highlights are seen:
layer filled with blue placed below the transparent shirt layer
layer filled with black placed below the transparent shirt layer
Does anyone have any ideas on how I might be able to accomplish this? I've been able to get close to the result, but my transparency is either not enough or too much. I lose much of the shadow/highlight detail. The starting image is of filetype JPG.
I need the final result to be a PNG like this one:
This PNG looks like it has a white background but taking it into Photoshop or GIMP you'll see the shirt is transparent. I need to reverse engineer how this was done so it can be done to other pieces of clothing.
What is interesting about the above PNG is the Shadows, Highlights, and Midtones in the transparent part of the image can all be selected individually. Photoshop: Select->Color Range->Shadows, Highlights or Midtones. Image below to show what I mean: