FreeImage.cs

using FreeImageAPI;

const int size = 150;

using (var original = FreeImageBitmap.FromFile(path))
{
    int width, height;
    if (original.Width > original.Height)
    {
        width = size;
        height = original.Height * size / original.Width;
    }
    else
    {
        width = original.Width * size / original.Height;
        height = size;
    }
    var resized = new FreeImageBitmap(original, width, height);
    // JPEG_QUALITYGOOD is 75 JPEG.
    // JPEG_BASELINE strips metadata (EXIF, etc.)
    resized.Save(OutputPath(path, outputDirectory, FreeImage), FREE_IMAGE_FORMAT.FIF_JPEG,
        FREE_IMAGE_SAVE_FLAGS.JPEG_QUALITYGOOD |
        FREE_IMAGE_SAVE_FLAGS.JPEG_BASELINE);
}