How can I set my image for 300 PPI?
You can change an image’s PPI in most graphics packages.
If working with an image you think you’ll need to print, it’s a good idea to set your target print resolution before you resize it. That will help to ensure you don’t make it too small to print safely at your preferred size.
How to Change the PPI in Photoshop
To change an image’s PPI in Photoshop, go to Image > Image Size. Uncheck Resample Image, because this setting will upscale your image, which will make it lower quality.
Now, next to Resolution, type in your preferred resolution, set as Pixels/Inch. Notice how the Width and Height figures change, too. This shows you the size your image will print.
You can, of course, specify the width and height instead, in inches or centimeters. If you do this, just make sure your PPI doesn’t drop too low to degrade the quality. You should be able to set your images width and height and keep the PPI at 300.
How to Change the PPI In GIMP
To change the PPI of an image in GIMP, go to Image > Print Size. Enter your preferred DPI next to X Resolution, set in pixels/in. The Y Resolution should update automatically, too.
Like in Photoshop, you can set the physical width and height instead. Again, make sure the PPI doesn’t drop too low when you do this.
How to Change the PPI In PixInsight
For more information on this tool, please check the reference documentation at the pixinsight.xom website https://pixinsight.com/doc/tools/Resample/Resample.html