Line art breaks normal resizing
Anime and manga are built from hard ink edges and flat fills. Ordinary interpolation — bilinear or bicubic — averages neighbouring pixels, which turns crisp black lines into soft grey ramps and makes flat areas blotchy [1][2]. Nearest-neighbour keeps edges hard but turns every curve into a staircase [1].
waifu2x: the first popular anime upscaler
Real-ESRGAN's anime model
Real-ESRGAN (2021) is trained on synthetic real-world damage — blur, noise, resizing and JPEG — so it handles screenshots and reposts that have been compressed several times [6]. Its authors also publish RealESRGAN_x4plus_anime_6B, a smaller model optimised for anime images [7]. Kenerate's default engine is Real-ESRGAN, which is why line art stays dark and clean.
Keep characters on-model
Generative upscalers can add texture that was never drawn — great for paintings, wrong for cel-shaded characters. The perception–distortion trade-off means more invented detail always costs some faithfulness [8]. For character art, stay with Real-ESRGAN or Image Upscaler and download PNG.
