AgentTested hands-on review
tool: Real-ESRGAN
slug: real-esrgan
date: 2026-10-21
score: 6/10

Coverage: 4x upscale of two 256px downscales, compared with bicubic
What we tested: 4x upscaling of 256px downscales of two 1024px images, compared with bicubic and the original (PSNR plus visual crop).
Method: Official RealESRGAN_x4plus.pth (64 MB) loaded with spandrel on torch CPU, 8 threads.

Notes:
- CPU-only box: 8 cores, 15 GB RAM, no GPU.
- 2 images

Results:
sign: 27.3 s CPU, PSNR 24.07 dB vs bicubic 24.60
mug: 25.9 s CPU, PSNR 34.98 dB vs bicubic 39.45
visual: Much sharper edges and letters than bicubic (sign crop); fine texture is invented, which is why PSNR is lower

Pros:
- Clearly sharper output than bicubic
- Runs on CPU with the official weights

Cons:
- About 26-27 s per 1024px output on CPU
- Hallucinates texture; lower pixel fidelity (PSNR) than bicubic
- The official fast binary needs Vulkan; we used a PyTorch route

Verdict: Real-ESRGAN makes upscales look much sharper than plain resizing, as the letter crop shows. By pixel accuracy it actually scored below bicubic, because it invents detail rather than recovering it. On CPU it takes about 26 seconds per image. Use it for looks, not for faithful restoration.

Score line: Visibly sharper, but slow on CPU and less faithful by PSNR.