Question

This is the code I cam up with to generate square thumbnail in C#

I havent’t code this type of thing before.
Since this code will be used heavily, I am checking with you before I put this in production.

Do you see anything bad or can be improved further?

Basically I have a set of thumbnails sitting in some folder.
Those thumbnails are not square and I need to make all of them square.
This will be called in a loop for each file in the folder.

This is how I call it:

SaveSquareThumb(75, "C:\storage\images\temp\thumbs", "C:\storage\images\thumbs");

public static void SaveSquareThumb(int squareSize, string sourcePath, string savePath)
        {
            using (Bitmap srcImage = new Bitmap(sourcePath))
            {
                int width = srcImage.Width;
                int height = srcImage.Height;

                int x = 0;
                int y = 0;

                //Determine dimensions of resized version of the image 
                if (width > height)
                {
                    width = (int)Decimal.Round(Convert.ToDecimal((decimal)squareSize * ((decimal)width / (decimal)height)), 0);

                    height = squareSize;
                    // moves cursor so that crop is more centered 
                    x = Convert.ToInt32(Math.Ceiling(((decimal)(width - height) / 2M)));
                }
                else if (height > width)
                {
                    height = (int)Decimal.Round(Convert.ToDecimal((decimal)squareSize * ((decimal)height / (decimal)width)), 0);
                    width = squareSize;
                    // moves cursor so that crop is more centered 
                    y = Convert.ToInt32(Math.Ceiling(((decimal)(height - width) / 2M)));
                }
                else
                {
                    width = squareSize;
                    height = squareSize;
                }

                // required in case thumbnail creation fails?
                Image.GetThumbnailImageAbort dummyCallback = new Image.GetThumbnailImageAbort(ThumbnailCallback);

                EncoderParameter qualityParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);
                ImageCodecInfo codecInfo = GetEncoderInfo("image/jpeg");
                EncoderParameters encoderParams = new EncoderParameters(1);
                encoderParams.Param[0] = qualityParam;

                //get thumbnail from source image
                using (Image thumb = srcImage.GetThumbnailImage(width, height, null, System.IntPtr.Zero))
                {
                    //Create a Crop Frame to apply to the Resized Image 
                    using (Bitmap myBitmapCropped = new Bitmap(squareSize, squareSize))
                    {
                        using (Graphics myGraphic = Graphics.FromImage(myBitmapCropped))
                        {
                            //Apply the Crop to the Resized Image 
                            myGraphic.DrawImage(thumb, new Rectangle(0, 0, width, height), x, y, width, height, GraphicsUnit.Pixel);

                            //Save the Croped and Resized image as a new square thumnail 
                            myBitmapCropped.Save(savePath, codecInfo, encoderParams);
                        }
                    }
                }
            }
        }

Answer 1

First two items are most important, third and fourth are all about code readability:

1. Add input parameters validation
2. Consider how method should behave if any of path parameters is not found
3. You have multiple casts of ((decimal)squareSize), ((decimal)width) consider single cast and store it in the new method level variables
4. You canset at the beginning of method default values for width and height to be equals to squareSize and then remove following code block:

   else
   {
      width = squareSize;
      height = squareSize;
   }