If I rasterize a vector, then make it a vector again, will quality be lost?

Yes But Predictive AI Helps

A vector is a mathematical formula that is resolution independent. No matter what scale it is, it always has infinite quality.

A raster, however, is resolution dependent and is made up of pixels and pixels aren’t infinite.

So by its very definition, a raster image is always less quality than a vector. Whether or not that is noticeable or not is a different matter.

A good quality raster will look identical to a vector if the raster perfectly matches the pixel definition of the screen it’s displayed on, but if it is resized or displayed on a screen with a higher pixel definition, it will have less quality than it’s vector counterpart.

If you try to make it a vector again (tracing), the vector will only match the raster pixels, therefore it will be less quality than the original.

Predictive AI

However, new algorithms are emerging that use predictive AI to make images higher quality when vectorising and resing as rasters.

This means that you can make your image higher quality than it was when it was a raster, but probably not as good as it was when it was its original vector.

Two artificial intelligence systems built by Google are able to
transform a heavily pixellated, low quality, image into a clear photo
or a person or object.

Computer scientists from Google Brain, the central Google AI team,
have shown it’s not only possible to enhance a picture’s resolution,
they can fill in missing details in the process. In a paper – Pixel
Recursive Super Resolution – three researchers from the Silicon Valley
firm trained their system on small 8×8 pixel images of celebrity faces
and photos of bedrooms.

Further reading: Deep Learning/AI

Magenta Machine Learning

Magenta is a research project exploring the role of machine learning
in the process of creating art and music. Primarily this involves
developing new deep learning and reinforcement learning algorithms for
generating songs, images, drawings, and other materials.

Machine Learning to Enhance Your Low-Res Photos

We’ve recently seen a number of interesting approaches to improving
low-resolution images using machine learning, including ones from
researchers at Google, and at the Max Planck Institute for Intelligent
Systems. Now, you can try an AI-powered enhancing tool for yourself
with just a couple of clicks.