About DPI Converter
Some print services and submission forms reject images that report a low DPI (like the 72 DPI that's typical of images saved for the web), even if the actual pixel dimensions are perfectly fine for printing. This tool edits that DPI metadata tag directly — for JPEG files it edits the JFIF density fields, and for PNG files it edits the pHYs chunk — without re-encoding or resampling the image in any way. The compressed pixel data inside the file is left completely untouched, byte for byte, so there is no quality loss whatsoever from using this tool.
Both JPEG and PNG are supported. If a file doesn't already have a DPI marker, one is added; if it already has one, it's updated in place.
DPI vs. Resolution: Why Changing DPI Alone Doesn't Improve Print Quality
DPI (dots per inch) is just a label telling a printer how large to print the existing pixels — it is not a measure of how much detail an image actually contains. An image that is 600×450 pixels contains exactly 600×450 pixels of real information whether its DPI tag says 72 or 300; changing the tag from 72 to 300 doesn't add a single new pixel of detail, it just tells the printer "print each inch of paper using more of these existing pixels," which makes the printed image physically smaller, not sharper.
What actually determines print quality is the pixel dimensions relative to the physical print size you want. As a rule of thumb, for good print quality you generally want the image's pixel dimensions to be about 300 times the intended print size in inches — for example, roughly 1800×1200 pixels for a good-quality 6×4 inch print. If your image doesn't have enough pixels for the print size you need, changing the DPI tag with this tool (or any tool) won't fix that — the image would need to be a higher resolution to begin with. This tool is genuinely useful when a print submission system is rejecting your file purely because of its DPI metadata, and your image already has enough real pixel detail for the print size you need.
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