Set any white pixels to transparent in ImageMagick using a threshold?

Using ImageMagick, I want to find any pixels that are white and make them transparent. I'm thinking the key is -threshold but I can't work o开发者_JS百科ut how to change a white pixel to transparent using -threshold. Any suggestions most appreciated.

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convert input.png -fuzz 10% -transparent white output.png

Note that the order of the arguments is important - -fuzz must come before -transparent.

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Would something like this work?

convert input.jpg -fuzz 5% -fill to_color -opaque from_color output.jpg