IntegerScaler is a free utility for pixel-perfect integer-ratio scaling (integer scaling) of games with no blur. For example, at the Full HD (1920×1080) resolution on a 4K monitor (3840×2160), each logical pixel is displayed as a square group of four (2×2) physical pixels of the same color.
Marat-Tanalin/integer-scaler
Free app for Windows 7+ for GPU-independent pixel-perfect (integer) scaling