John’s Image Converter

John’s Image Converter is a resourceful utility that enables you to convert graphic files between various formats in bulk. It offers support for JPG, GIF, BMP, PNG, TIFF and WMF, and has other advanced features, such as image resizing and rotating.

The setup procedure doesn't take long and the only notable aspect about it is that you must have .NET Framework installed.

Regarding the GUI, John’s Image Converter opts for a normal-looking window with a neatly organized structure. It's split into three panes for converting one image and a folder, as well as for putting together a montage.

Apart from the fact that you can pick the preferred output image format and saving directory, it's possible to set the new filename, height and weight (pixels or percent), constrain proportions, as well as rotate the photos by 90 degrees to the left or right. However, these options are available only for single file conversion.

When it comes to batch processing mode, you can choose the source and destination folders, set a new size for all pics, enter a string of characters to append to the filenames, as well as ask the tool to auto-rotate the pictures when there's EXIF orientation information preset (JPEGs) and to overwrite any existing files without confirmation.

Lastly, the montage mode gives you the possibility to create a photo pile of polaroids or postcards, a four-picture photo montage, or a mosaic image. You can set the dimensions of the whole montage and individual snapshots, use a random background picture, and suppress captions on individual snapshots.

It finished conversion, resizing and rotation tasks swiftly while remaining light on system resources consumption. Thanks to its advanced, yet approachable options, John’s Image Converter should meet the requirements of many users. Plus, it's free.