Occasionally, images may appear horizontally or vertically stretched in Windows Photo Viewer.1 One possible explanation for this is that somewhere along the way the images’ metadata for their x and y-resolutions became corrupted. In order to correct this, you need to edit the images’ metadata. ExifTool is one of the best programs for editing metadata.
How to Edit Image Metadata with ExifTool
1. Download ExifTool. If you don’t know Perl (a programming language), I recommend downloading the stand-alone Windows executable, or the Mac OS X package if you’re a Mac user. ExifTool is lightweight (3.5 MB) and portable, so you don’t need to worry about it cluttering up your system.
2. Unzip the executable file.
3. Read your image’s metadata. You can read your image’s metadata by dragging and dropping your image into the exiftool(-k).exe icon or opening it with exiftool(-k).exe (Open with > Choose program > Browse > exiftool(-k).exe). Check your x and y-resolution values.
You can also read your images’ metadata with this online Exif viewer: http://regex.info/exif.cgi
4. Edit your image’s metadata. If you’re comfortable with using the command line, rename the executable file “exiftool.exe” and use the command line. If, like me, you’re not, you can run operations by renaming the executable file. Rename the executable file “exiftool(-Xresolution=100 -Yresolution=100 -overwrite_original).exe”. Then drag and drop the image into the renamed executable file or open the image with the renamed executable file. After you follow these steps, the image’s x-resolution metadata will be rewritten to 100 and the y-resolution to 100. The image should now appear with the correct dimensions in Windows Photo Viewer.
1 I recommend using Irfanview as your default image viewer.