24-bit PNG - troubles adding an alpha

[rkwright]

OK - I feel like I'm missing something. I have a 24-bit PNG that has a background value of 254,254,254 that needs to be made transparent.

I haven't had luck with any combination of the flags below (using nconvert 5.60):L

-ctype rgba
-add_alpha "value" (what is "value" supposed to represent? Can't find info in docs)
-merge_alpha
-transpcolor 254 254 254

Any thoughts on how to make an RGB png into an RGBA, with 254,254,254 having an alpha of 0?

I'd appreciate it.

[xnview]

-add_alpha "value" (what is "value" supposed to represent? Can't find info in docs)

value is the alpha that you want to add

[krawhitham]

-add_alpha "value" (what is "value" supposed to represent? Can't find info in docs)

value is the alpha that you want to add

Code: Select all

nconvert.exe -out tga -add_alpha alpha.tga -overwrite main.tga

produces a 100% black alpha channel in main.tga

I'm I using the wrong command?

[xnview]

no -add_alpha 255