Standardize coding style and clean up some branching logic#25

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lstomberg wants to merge 3 commits intosmallmuou:masterfrom

lstomberg:master

Commits on Dec 4, 2019

Standardize coding style, remove unused functions, clean up some branching logic
lstomber
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Add warning and resolution if source image has alpha channel
lstomber
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Commits on Dec 10, 2019

Support optional -n argument to specify generated filename
lstomber
committed