Could you please explain the bold と and に? Do both of them indicate "become"?
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As for the と, it's probably "と for resultant form". So yes, the idea is that the snow made the 町並み turn into 影. Outside of set phrases such as 露と消える and 無用の長物と化す, this type of と is rare and highly stilted. I had to read this several times before I became almost certain about the role of this と.
As for the に, it's a destination marker (to or into in English) in a broad sense, but here it marks the resultant state (己の色 = 雪の純白) rather than a place. 純白に侵食する can be understood as something similar to 純白に染める or 純白に変える, but に in ～に浸食する usually marks a place.