c# - Select an image from rectangle using writeablebitmap -

i have written application in silverlight, placing rectangle on image , want select part of image covered rectangle , show on image control on click of button.

i not @ handling ratios , image manipulation things, unable right way.

the code same goes below, , appreciate, if suggest me way or solution around this.

public void captureimage(object sender, routedeventargs e) {             bitmapimage bitmapimage = new bitmapimage();             //// bitmapimage.createoptions = bitmapcreateoptions.none;             bitmapimage = newimage;              ////calculate bounding box             int originalwidth = bitmapimage.pixelwidth;             int originalheight = bitmapimage.pixelheight;              int newsmallwidth = (int)squareblue.width;             int newsmallheight = (int)squareblue.height;              ////generate temporary control render image             image temporaryimage = new image { source = bitmapimage, width = newsmallwidth, height = newsmallheight };              ////create writeablebitmap             writeablebitmap wb = new writeablebitmap(newsmallwidth, newsmallheight);              translatetransform t = new translatetransform();             t.x = -5;             t.y = -5;              wb.render(temporaryimage, t);              wb.invalidate();              myimage.source = wb;    } 

whenever code gets executed, whole image gets snapped, instead of part selected rectangle. anyone, guide me doing wrong here.

i'd recommend use crop method writeablebitmapex library provides.