Alongside JPEG (or JPG), PNG is one of the most common image formats on the Internet. All Windows 7 and 8 computers include two programs that can open Portable Network Graphics files. Windows Photo Viewer is best for looking at a picture or printing a copy. To edit an image or save it in another image format, use Paint.
Double-click a PNG image to open it in the default image viewing or editing program.
Out of the box, Windows 7 and 8 use Windows Photo Viewer as the default. Even if you change the default program later, you can always open a PNG in Windows Photo Viewer by right-clicking the image and selecting Preview.
Use the buttons along the bottom of Windows Photo Viewer to work with the image.
The left two buttons adjust the zoom. The middle panel moves back and forth through images in the same folder, and the center button starts a slideshow. On the right, the circular arrows rotate the image and the "X" icon deletes the image.
Other than rotating the image, Windows Photo Viewer can't permanently edit an image -- zooming in and out does not actually shrink or expand the image file.
Use the menu at the top for file operations, such as to make a copy of the image, print it, email it, burn it to a disc or open it in another program.
Open a PNG directly in an image editing program from Windows by right-clicking the image and choosing Open With. Unless you have another editor installed, pick Paint to open the image editor included with Windows.
To change the default editor for PNG files, click Choose Default Program and choose a program. The program you pick opens instead of Windows Photo Viewer when you double-click any PNG.
Work with the image in Paint, resizing, cropping and editing as needed. When you're done, open the File menu (a menu icon on Windows 7) and choose Save. To change to another image format, point to Save As and pick the new format. When you use Save As, you create a new copy of the file with your changes, leaving the original untouched.
Unlike Windows Photo Viewer in older versions of Windows, the program in Windows 7 and 8 does not display scroll bars when you open large images. To scroll an image, click and drag anywhere on the picture.
In Windows Photo Viewer, the left and right arrow keys move between images in the current folder. The mouse wheel zooms in and out.
You can edit and save a PNG as many times as you want without losing image quality, but saving a file as a JPEG causes compression artifacts, lowering quality. PNG files also support transparent backgrounds, unlike JPEG files, so if you change to JPEG, any transparent backgrounds turn solid white.