ImageResizer

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;

namespace Core.Drawing {

    public class ImageResizer {

        public static void ResizeImage(string originalFile,string newFile,Size size,bool resizeExactly = false) {
            ResizeImage(originalFile,newFile,size.Width,size.Height,resizeExactly: resizeExactly,onlyResizeIfWider:false);
        }
        public static void ResizeImage(string originalFile,string newFile,int newWidth,int maxHeight,bool resizeExactly, bool onlyResizeIfWider = false) {

            using(Image fullsizeImage = Image.FromFile(originalFile)) {

                // Prevent using images internal thumbnail
                fullsizeImage.RotateFlip(System.Drawing.RotateFlipType.Rotate180FlipNone);
                fullsizeImage.RotateFlip(System.Drawing.RotateFlipType.Rotate180FlipNone);
                int newHeight = maxHeight;

                if(resizeExactly == false) {
                    if(onlyResizeIfWider) {
                        if(fullsizeImage.Width <= newWidth) {
                            newWidth = fullsizeImage.Width;
                        }
                    }

                    newHeight = fullsizeImage.Height * newWidth / fullsizeImage.Width;
                    if(newHeight > maxHeight) {
                        // Resize with height instead
                        newWidth = fullsizeImage.Width * maxHeight / fullsizeImage.Height;
                        newHeight = maxHeight;
                    }
                }

                using(Image newImage = fullsizeImage.GetThumbnailImage(newWidth,newHeight,null,IntPtr.Zero)) {

                    // Clear handle to original file so that we can overwrite it if necessary
                    fullsizeImage.Dispose();

                    // Save resized picture
                    newImage.Save(newFile);
                }
            }
        }
    }
}