QML can load files specified with encoded characters (for example, "file:/tmp/test%23123/test.png", where the '#' character is percent-encoded), but not when the directory separators are encoded.

For example, encoding the entire path as done here:

source: "file:" + encodeURIComponent("/tmp/test#123/test.png")

results in the error:

file://<$PWD>%2Ftmp%2Ftest%23123%2Ftest.png: File not found

(where <$PWD> is the working directory at invocation)

This can be worked around via a helper function:

function encodeURIComponents(uri) {
    return uri.split('/').map(encodeURIComponent).join('/')
}

source: "file:" + encodeURIComponents("/tmp/test#123/test.png")