Resize Image But Wrong Border Color (Black 'Auto')

Question

    public Image resizeImage(int newWidth, int newHeight, string stPhotoPath)
    {
        Image imgPhoto = Image.FromFile(stPhotoPath);

        int sourceWidth = imgPhoto.Width;
        int sourceHeight = imgPhoto.Height;

        if (sourceWidth < sourceHeight)
        {
            int buff = newWidth;

            newWidth = newHeight;
            newHeight = buff;
        }

        int sourceX = 0, sourceY = 0, destX = 0, destY = 0;
        float nPercent = 0, nPercentW = 0, nPercentH = 0;

        nPercentW = ((float)newWidth / (float)sourceWidth);
        nPercentH = ((float)newHeight / (float)sourceHeight);
        if (nPercentH < nPercentW)
        {
            nPercent = nPercentH;
            destX = System.Convert.ToInt16((newWidth -
                      (sourceWidth * nPercent)) / 2);
        }
        else
        {
            nPercent = nPercentW;
            destY = System.Convert.ToInt16((newHeight -
                      (sourceHeight * nPercent)) / 2);
        }

        int destWidth = (int)(sourceWidth * nPercent);
        int destHeight = (int)(sourceHeight * nPercent);


        Bitmap bmPhoto = new Bitmap(newWidth, newHeight,
                      PixelFormat.Format24bppRgb);

        bmPhoto.SetResolution(imgPhoto.HorizontalResolution,
                     imgPhoto.VerticalResolution);

        Graphics grPhoto = Graphics.FromImage(bmPhoto);
        grPhoto.Clear(Color.Black);
        grPhoto.InterpolationMode =
            System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

        grPhoto.DrawImage(imgPhoto,
            new Rectangle(destX, destY, destWidth, destHeight),
            new Rectangle(sourceX, sourceY, sourceWidth, sourceHeight),
            GraphicsUnit.Pixel);

        grPhoto.Dispose();
        imgPhoto.Dispose();
        return bmPhoto;
    }

I use such a code to scale down images, but there is a problem that after the images are scaled down, the remaining spaces remain black. Something that should definitely not happen. What is the solution? The background color must be white.

Answer 1

public static  class ResizeImage
{
        /// <summary>
   /// Return new resized size to display the image
     /// </summary>
   /// <param name="srcrectanle">source rectangle of image or you can pass the 
    bitmap and set the size accrodingly</param>
/// <param name="initSize">initial size of the page to draw image</param>
/// <returns></returns>
public static SizeF getResizedRectangle(RectangleF srcrectanle, SizeF initSize)
{
    float sw = srcrectanle.Width;
    float sh = srcrectanle.Height;
    float dw = initSize.Width;
    float dh = initSize.Height;
    float finalHeight, finalWidth;
    float Sourceratio = sw / sh;

    if (Sourceratio >= 1)
    {
        finalWidth = (int)dw;
        float ratio = sw / dw;
        finalHeight = (sh / ratio);
    }
    else
    {
        finalHeight = (int)dh;
        float ratio = sh / dh;
        finalWidth = (sw / ratio);
    }
    return new SizeF(finalHeight, finalHeight);
}
}

Use this function to resize your image. Hope you have the knowledge of source rectangle and destination rectangle.