I'm attempting to convert the cover art I created for my latest novel from 96 DPI to 300 DPI. The original image looks fine for Kindle purposes but the current DPI only allows it to take up about 70% of the paperback's cover. Amazon recommends 300 DPI so I assume this will allow me to size the image properly for the paperback. As with the initial creation, my tools are MS Paint and Irfanview.
As you might imagine, simply upscaling the image in Irfanview from 96 DPI to 300 DPI degrades the quality too much, but that didn't come as a surprise. So I went back to the original B&W template and tried upscaling that. It looks fine at first glance, with very little aliasing. However, when I tried to add color and paste it into the background image, I discovered remnants or artifacts from the upscaling that turned my supposedly white background into a barely perceptible pastiche of off-white and dull gray. So, right now my options are to start from scratch with a blank 300 DPI image, or go in like a surgeon and try to remove the artifacts. Both choices are time consuming.
Any tips or tricks I'm missing, or am I pretty much stuck going back to the drawing board?