If you’re trying to print a PNG file, you may need to know the DPI or dots-per-inch of the image. A printer uses millions of dots of ink to compile your print. The DPI tells the printer how many dots need to go in a given square inch, so if you have a 300dpi—there will be 300 dots of ink per square inch. Not all image files have the same properties, so do PNG files have a DPI?
PNG files do have DPI, and there are several ways you can find the DPI of a PNG file. You can use a program, which depends on your computer system. You can also find your answer in the image metadata, but it requires some conversion.
Depending on the resolution and size you want, the dpi may need to change. For instructions on finding the dpi of your PNG file and how to change it, keep reading.
Getting into the logistics of the dpi of a PNG image can be confusing when correlating that to the size and resolution you need for your print. Before you can change anything, you need a base number to start. Then you can see how changing these variables will affect the overall print, referring to size and image quality. There are several ways to find the dpi of your PNG file.
1. Open Your PNG File in a Photo Viewer
Depending on the computer system you are operating on, you will either use Paint for Windows or Preview for Mac. Open your image in either of these programs and navigate to the image properties or dimensions.
In Preview, you will go to Tools>Adjust Size. A dialogue box will appear to show you several bits of information about the image, including the “Resolution.” The resolution is shown in pixels/inch— that is your dpi. In Paint, you will go to File>Properties, and a dialogue box will appear, and the dpi will be shown under File Attributes>Resolution.
1. Open Your PNG File in a Design Program
If you would rather use a design program to view the dpi of your PNG file, in case you want to change it, you can use a design program like Photoshop. Once you’ve opened your image in Photoshop, go to Image>Image Size, and you will see your dpi under “Resolution.”
If you want to change the dpi of your PNG file, you will need to uncheck “Resample “Image” as it will attempt to upscale your image, affecting the quality. When you change the resolution, you will notice that the height and width will change. You can always opt to change these dimensions in inches and centimeters instead. If you do, just keep an eye on the dpi. You don’t want it to drop too low; otherwise, the quality will be adversely affected.
1. Look at the Metadata of Your PNG File
Locating the metadata of your PNG file may be the most obscure of the suggestions, but when all else fails, you have a backup option. In the PNG file, two 4-byte numbers give the height and width of the image in pixels/meter. In order to convert this to dpi, you will need to multiply those numbers by 0.0254 meters/inch.
There has already been one suggestion on changing the dpi of your PNG file in this article via Photoshop. The same action can be done in Paint (Windows) and Preview (Mac). If you need more options, there are some alternatives. You can use an image editor to change the dpi, like GIMP, a cross-platform free software for editing images. In GIMP, you would go to Image>Print Size and make your adjustments.
You can also use an online converter for free. It will allow you to select the dpi you want; typical dpi choices are 72, 150, 200, 300, up to 600+. After selecting, you’ll upload your image, and the converter will do the rest.
No matter the image, there is a way to get just the right harmony between print size and resolution, so you’re getting the print you want without sacrificing the quality. It may be a delicate balance, but it’s one worth playing around with to see what works best for you.