This is a very versatile small program, which I find very handy and provided many features to edit and enhance image files.
You can also just download the portable version and take the program with you in a pen drive, without installing in the computer you need to use for editing your images.
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Under the 'Edit' pull down menu you can find many options to choose for enhacing the images. Although the available options are not as extensive as some other tools but I find that they are quite sufficient for normal use.
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There is a 'draw board' feature, which will take you to a screen where many drawing options you can add such as callouts, lines, ellipse, rectangle or even to add watermark image.
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This is a freeware program where you can download it from:
http://www.faststone.org/index.htm