Source Code for Module screenBitmap

 1  import ctypes 
 2  import winGDI 
 3   
 4  user32=ctypes.windll.user32 
 5  gdi32=ctypes.windll.gdi32 
 6   
 7 -class ScreenBitmap(object): 
 8          """Provides a way to capture a bitmap of any part of the screen. The object caches needed DCs and bitmaps therefore an instance of an object only handles one size of bitmap.""" 
 9   
10 -        def __init__(self,width,height): 
11                  """ 
12                  @param width: the width of the resulting bitmap in rgb pixels. 
13                  @param height: the height of the bitmap in rgb pixels. 
14                  """ 
15                  self.width=width 
16                  self.height=height 
17                  #Fetch the device context for the screen 
18                  self._screenDC=user32.GetDC(0) 
19                  #Create a memory device context with which we can copy screen content to on request. 
20                  self._memDC=gdi32.CreateCompatibleDC(self._screenDC) 
21                  #Create a new bitmap of the chosen size, and set this as the memory device context's bitmap, so that what is drawn is captured. 
22                  self._memBitmap=gdi32.CreateCompatibleBitmap(self._screenDC,width,height) 
23                  self._oldBitmap=gdi32.SelectObject(self._memDC,self._memBitmap) 
24                  #We always want standard RGB data 
25                  bmInfo=winGDI.BITMAPINFO() 
26                  bmInfo.bmiHeader.biSize=ctypes.sizeof(bmInfo) 
27                  bmInfo.bmiHeader.biWidth=width 
28                  bmInfo.bmiHeader.biHeight=height*-1 
29                  bmInfo.bmiHeader.biPlanes=1 
30                  bmInfo.bmiHeader.biBitCount=32 
31                  bmInfo.bmiHeader.biCompression=winGDI.BI_RGB 
32                  self._bmInfo=bmInfo 
33   
34 -        def __del__(self): 
35                  gdi32.SelectObject(self._memDC,self._oldBitmap) 
36                  gdi32.DeleteObject(self._memBitmap) 
37                  gdi32.DeleteDC(self._memDC) 
38                  user32.ReleaseDC(0,self._screenDC) 
39   
40 -        def captureImage(self,x,y,w,h): 
41                  """ 
42                  Captures the part of the screen starting at x,y and extends by w (width) and h (height), and stretches/shrinks it to fit in to the object's bitmap size. 
43                  """ 
44          #Copy the requested content from the screen in to our memory device context, stretching/shrinking its size to fit. 
45                  gdi32.StretchBlt(self._memDC,0,0,self.width,self.height,self._screenDC,x,y,w,h,winGDI.SRCCOPY) 
46                  #Fetch the pixels from our memory bitmap and store them in a buffer to be returned 
47                  buffer=(winGDI.RGBQUAD*w*h)() 
48                  gdi32.GetDIBits(self._memDC,self._memBitmap,0,self.height,buffer,ctypes.byref(self._bmInfo),winGDI.DIB_RGB_COLORS); 
49                  return buffer 
50   
51 -def rgbPixelBrightness(p): 
52          """Converts a RGBQUAD pixel in to  one grey-scale brightness value.""" 
53          return int((0.3*p.rgbBlue)+(0.59*p.rgbGreen)+(0.11*p.rgbRed)) 
54