c# convert image to byte array -

i loooking faster solution convert image byte array using regular method:

   public byte[] imagetobytearray(system.drawing.image imagein)  {   memorystream ms = new memorystream();   imagein.save(ms,system.drawing.imaging.imageformat.gif);   return  ms.toarray();  } 

so searched , found one

public static byte[] bitmaptobytearray(bitmap bitmap)     {          bitmapdata bmpdata = bitmap.lockbits(new rectangle(0, 0, bitmap.width, bitmap.height), imagelockmode.readonly, bitmap.pixelformat);         int numbytes = bmpdata.stride * bitmap.height;          numbytes = math.abs(numbytes);          byte[] bytedata = new byte[numbytes];         intptr ptr = bmpdata.scan0;          marshal.copy(ptr, bytedata, 0, numbytes);          bitmap.unlockbits(bmpdata);          return bytedata;      } 

this call:

 `   private void form1_load(object sender, eventargs e)     {         bitmap curr = getdesktopimage();          byte[] buff = bitmaptobytearray(curr);           } 

than got expcetion arithmetic operation resulted in overflow , discoverd numbofbytes negative couldn't make array used math.abs() got error on line marshal.copy(ptr, bytedata, 0, numbytes); , error : attempted read or write protected memory. indication other memory corrupt. why happening? getdesktopimage() method have uses gdi take screenshots according this , method actully (i tried display on picturebox) im facing weird errors when trying convert bytes..

this getdesktopimage()

 public static bitmap getdesktopimage()     {         //in size variable shall keep size of screen.         size size;          //variable keep handle bitmap.         intptr hbitmap;          intptr hdc = platforminvokeuser32.getdc(platforminvokeuser32.getdesktopwindow());          intptr hmemdc = platforminvokegdi32.createcompatibledc(hdc);          size.cx = platforminvokeuser32.getsystemmetrics(platforminvokeuser32.sm_cxscreen);          size.cy = platforminvokeuser32.getsystemmetrics(platforminvokeuser32.sm_cyscreen);          hbitmap = platforminvokegdi32.createcompatiblebitmap(hdc, size.cx, size.cy);          if (hbitmap != intptr.zero)         {              intptr hold = (intptr)platforminvokegdi32.selectobject(hmemdc, hbitmap);              platforminvokegdi32.bitblt(hmemdc, 0, 0, size.cx, size.cy, hdc, 0, 0, platforminvokegdi32.srccopy);              platforminvokegdi32.selectobject(hmemdc, hold);              platforminvokegdi32.deletedc(hmemdc);              platforminvokeuser32.releasedc(platforminvokeuser32.getdesktopwindow(), hdc);              bitmap bmp = system.drawing.image.fromhbitmap(hbitmap);              platforminvokegdi32.deleteobject(hbitmap);              gc.collect();              return bmp;         }           return null;     } 

for negative stride, msdn doc says:

the stride width of single row of pixels (a scan line), rounded four-byte boundary. if stride positive, bitmap top-down. if stride negative, bitmap bottom-up.

your bitmap bottom-up. have @ nice explanation here: https://msdn.microsoft.com/en-us/library/windows/desktop/aa473780(v=vs.85).aspx

to copy bytes, need calculate starting address in answer: https://stackoverflow.com/a/17116072/200443.

if want reverse bytes order, need copy 1 line @ time.