DPI (dots per inch) determines the print resolution of an image. For professional printing, 300 DPI is the standard. For home printing, 150-200 DPI is often sufficient. For screen display, DPI is irrelevant since screens display images pixel-for-pixel.
Changing DPI without changing pixel dimensions only affects the metadata that tells printers how large to print the image. A 3000x2000 pixel image at 300 DPI prints at 10x6.67 inches. The same image at 150 DPI prints at 20x13.33 inches but with lower print quality.
To increase print quality, you need more pixels, not just higher DPI metadata. A 600x400 pixel image at 300 DPI can only print sharply at 2x1.33 inches.
With ImgTools, focus on getting the correct pixel dimensions for your print size. Calculate needed pixels: print size (inches) x 300 = pixels needed. Then resize to those dimensions.
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