Today I am doing a tutorial on changing a photo's resolution using the software called Fotosizer which you can download here: http://www.fotosizer.com/Download.aspx
Once you have downloaded it then you should open it and install it, after that run it and it should look like this.
Now select the image you want to increase the resolution of and then change the resolution as you see fit by increasing the height and width. There is one thing I should mention the photo can become lighter or darker when you increase or decrease the resolution but you can fix this using the brightness settings. when you are done it will save it as a new image.
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