How can I convert a low-quality image to high-quality without watermark?

What if you want to convert low-quality images into high-quality ones, but don’t want to upload the files to some unknown cloud service? You can use Waifu2x-ncnn-vulkan, a reliable tool that runs locally and utilises artificial intelligence to enlarge images whilst reducing noise. It is particularly well-suited to photos with noticeable compression artefacts or blurring, and supports batch processing.

To get started, download the latest Windows version from the GitHub releases page (search "waifu2x-ncnn-vulkan" on GitHub). Extract the zip file to a folder, then open Command Prompt in that folder and run:

waifu2x-ncnn-vulkan -i input.jpg -o output.png -s 2

This command upscales the image by 2x. You can change -s 2 to -s 4 for 4x scaling, and add -n 2 to apply noise reduction if the original image is grainy. The tool supports batch processing and GPU acceleration for faster results.

If you’re looking to convert low-quality images into high-quality ones, Waifu2x-ncnn-vulkan can do the job without the need for additional software or uploading. Whilst it isn’t the most beginner-friendly tool, once the commands are set up, it gets the job done quickly. Please note that the results depend on the quality of the original image—some photos may reveal the tool’s limitations, but in most cases it delivers a noticeable improvement.