DPI vs resolution

These get used interchangeably and they are not the same thing at all. One is the image; the other is a note about how to print it.

Resolution is the image

Pixel dimensions — 3000 × 2000, say. That is all the detail that exists. Nothing you do to a metadata field adds any.

DPI is an instruction for a printer

Dots per inch tells a printer how large to render those pixels on paper. A 3000 × 2000 image at 300 DPI prints at 10 × 6.7 inches. The same file at 150 DPI prints at 20 × 13.3 inches — bigger and coarser. The pixels never changed; only the instruction did.

What "300 DPI" usually means when someone asks

They almost always mean "big enough to print well at the size we are printing it". Translate the request into pixels: multiply the print size in inches by 300.

If your image already has those pixels, it will print well regardless of what the DPI field says — the print software works out the rest.

What Dexta does

Dexta has no DPI control. Resize Image changes pixel dimensions, which is the thing that actually determines print quality, and the tools do not write a DPI tag. For screen use that is exactly right. If a print shop insists on a specific DPI value in the file, you will need software that edits that metadata — but check first whether they simply want a larger image.

Mistakes worth avoiding

• Changing the DPI field and expecting a sharper image. It changes the intended print size and nothing else.
• Upscaling to reach a pixel count for print. Interpolated pixels do not print as detail.
• Worrying about DPI for anything that will only be viewed on a screen.