Very much so. PNGは8ビットアルファチャネルと16ビットのオプション深さを持つ無損失DEFLATEで、再保存時に劣化しませんが、写真コンテンツでは大きくなります。. That determines both the headroom available and whether the saving costs you anything in fidelity.
透明度の決定は，透明度の変更を行う段階である。 That is the step most people actually came for, and doing it after PNG を圧縮 rather than before it means the conversion works from the file you finally settled on.
