如何选择ImageGrab.grab（）在多显示器设置中抓取哪个屏幕？

Question

就像标题所说，我很好奇是否有办法配置ImageGrab.grab（）模块来抓取，例如，在多显示器设置中，而不是左边的屏幕。

Answer 1

Unfortunately it isn't possible, due to the manner in which the PIL obtains the dimensions of the display device. When it obtains the Device Context, it does obtain one for all attached monitors:

screen = CreateDC("DISPLAY", NULL, NULL, NULL); 

( display.c , line 296, version 1.1.7)

However, to get the display dimensions, it uses this code:

width = GetDeviceCaps(screen, HORZRES);
height = GetDeviceCaps(screen, VERTRES);

( display.c , lines 299-300, version 1.1.7)

Which only returns the dimensions of the primary, active monitor. All subsequent operations are done with these width and height values, resulting in a final image that is only the size of the primary display.

---

In order to receive a screengrab of all attached monitors, those two lines would need to be replaced with something like:

width = GetSystemMetrics(SM_CXVIRTUALSCREEN);
height = GetSystemMetrics(SM_CYVIRTUALSCREEN);

After which you'd need to recompile PIL. This would provide you with the dimensions of the virtual screen, which is "... the bounding rectangle of all display monitors." [ MSDN ]

A more correct implementation would be using EnumDisplayMonitors to obtain device contexts for the individual monitors, along with altering ImageGrab.grab()'s interface (or adding a new function) to allow for the selection of a specific monitor, of whose device context would be used for the remaining operations.