缩放图像时的差异

我需要缩放图像，我有使用图形来做它的问题。我使用DrawImage，传递原始图像，新位置(0,0)和新尺寸。结果图像被缩放，但其上边缘和左边缘是透明的。有人知道为什么吗?我的代码:

Rectangle DstRec = new Rectangle(0, 0, (int) (CurrentImage.ImgBM.Width * Zoom), (int) (CurrentImage.ImgBM.Height * Zoom));
//ReducedBM = new Bitmap((int)(CurrentImage.ImgBM.Width * Zoom), (int)(CurrentImage.ImgBM.Height * Zoom));
ReducedBM = new Bitmap(CurrentImage.ImgBM, DstRec.Width, DstRec.Height);
Graphics g = Graphics.FromImage(ReducedBM);
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
//g.DrawImage(CurrentImage.ImgBM, 0, 0, (int)(CurrentImage.ImgBM.Width * Zoom), (int)(CurrentImage.ImgBM.Height * Zoom));
g.DrawImage(CurrentImage.ImgBM, DstRec);
g.Dispose();