Waifu2x is an online photo enhancer and image upscaler tool that enlarges images without losing quality. Also, get image noise reduction technology.
Bigjpg - 使用人工智能深度卷积神经网络（CNN）智能无损免费放大图片，可放大4K级超高清分辨率（4000x4000）图片，最大32倍放大,效果秒杀PhotoZoom放大。
