It is the plug-resynth-enlarge.py plugin ("Enlarge image and synthesize to sharpen.")
I can not really recommend it these days, it does date back to 2010, and there are better options for Gimp 2.10
I have in the past compared many of the 'convenience' options. The Gimp ML plugin, the ReShade program, various g'mic filters, ImageMagick, XnView. Not much difference between any of them and basic Gimp tools. Much depends on how horrible the source image is, but great if you are not bothered about how Gimp works.
Gimp resize using NoHalo interpolation is basically very good. Depending on how bad the original image is (for example, jpeg artifacts) a small median blur for smoothing, then upscale resize, then a sharpen with wavlet-decompose can give a decent result.
...but going back to the original question increase image size ... without reducing its quality? Whatever method used, is guessing pixels and there is some degradation.
edit: you can get the python-resynth plugins here: https://www.gimp-forum.net/attachment.php?aid=6497
I can not really recommend it these days, it does date back to 2010, and there are better options for Gimp 2.10
I have in the past compared many of the 'convenience' options. The Gimp ML plugin, the ReShade program, various g'mic filters, ImageMagick, XnView. Not much difference between any of them and basic Gimp tools. Much depends on how horrible the source image is, but great if you are not bothered about how Gimp works.
Gimp resize using NoHalo interpolation is basically very good. Depending on how bad the original image is (for example, jpeg artifacts) a small median blur for smoothing, then upscale resize, then a sharpen with wavlet-decompose can give a decent result.
...but going back to the original question increase image size ... without reducing its quality? Whatever method used, is guessing pixels and there is some degradation.
edit: you can get the python-resynth plugins here: https://www.gimp-forum.net/attachment.php?aid=6497