c# - A generic error occurred in GDI+, Getting this exception in my code when i try to save optimized image on server -

here code below using redraw , save image.

bitmap bitmap = new bitmap(httpcontext.current.server.mappath(     filepath + path.getfilename(filename)));  int newwidth = 100; int newheight = 100;  int iwidth = bitmap.width; int iheight = bitmap.height;  if (iwidth <= 100)     newwidth = iwidth;  if (iheight <= 100)     newheight = iheight;  bitmap.dispose();  // once got information, we'll process it.  // create image object using original width , height. // define pixel format (for rich rgb color).  system.drawing.image objoptimage = new system.drawing.bitmap(newwidth, newheight,      system.drawing.imaging.pixelformat.format16bpprgb555);  // original image. using (system.drawing.image objimg =     system.drawing.image.fromfile(httpcontext.current.server.mappath(filepath + filename))) {      // re-draw image using newly obtained pixel format.     using (system.drawing.graphics ographic = system.drawing.graphics.fromimage(objoptimage))     {         var _1 = ographic;         system.drawing.rectangle orectangle = new system.drawing.rectangle(0, 0, newwidth, newheight);          _1.drawimage(objimg, orectangle);     }  // on below lines of code getting error while try execute  // code after uploading image. if image size around 10 kb  // not throw error if exceeds 10 kb will.                //save optimized image     objoptimage.save(httpcontext.current.server.mappath(filepath + "tempsubimages/" + filename),         system.drawing.imaging.imageformat.png);**      objimg.dispose(); }  objoptimage.dispose();  // show optimized image details size. bitmap bitmap_opt = new bitmap(httpcontext.current.server.mappath(filepath + "tempsubimages/" + path.getfilename(filename))); byte[] bytes = system.io.file.readallbytes(httpcontext.current.server.mappath(filepath + "tempsubimages/" + path.getfilename(filename)));  ui.basepage.temporaryfile = bytes; string[] arrcontenttype = new string[] { postedfile.contenttype, filename }; ui.basepage.temporarystrings = arrcontenttype;  int iwidth_opt = bitmap_opt.width; int iheight_opt = bitmap_opt.height; bitmap_opt.dispose();