Open your photo editing software.
Select "File," then "Open," from the program toolbar. Use the file browsing window to locate the image that you wish to retouch.
Select "Image," then "Resize," to open the resizing menu. Use this menu to select a slightly smaller image size, between 75 percent and 90 percent of the original. This will cause the image editing program to re-render the image, which will automatically smooth many jagged lines. This alone probably will not solve the problem entirely.
Add a new layer to your image by pressing "CTRL"+"D" at the same time. Right-click this layer and select "Add Alpha Mask." This will prime your image for a very subtle blur effect that should completely eliminate the anti-aliased edges.
Select "Filter," then "Blur," to display a list of the blur options available. Select "Gaussian" from the list of available filters, then enter "1.5" in the "Pixel" text box. This will add a very slight Gaussian blur to the entire image, which will naturally round rough edges at a pixel level. This should make the image look a lot cleaner.