It is simply not possible to enlarge a raster image 2, 3, 4 times its size or more and retain overall quality. In all cases there will be quality loss. The greater the enlargement, the more quality loss generally occurs.
What software you use for such an enlargement is typically irrelevant. The nature of the transformation is inherently bad based up how raster images (jpg, png) are constructed.
This is, admittedly, a generalization. However, pixel-based images by nature are not designed to retain quality if they are enlarged.
- Some software, such as Photoshop, may interpolate pixel data making minor enlargements acceptable.
- Some output methods don't require high-quality images (billboards, banners, etc).
- Small images with a high PPI (pixels per inch) setting can often be enlarged while lowering the PPI, creating acceptable results.
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