巧用win32print来控制windows系统打印机并推送打印任务

　　小爬最近的一个需求是：将windows系统下的打印任务批量有序给到网络打印机。

用户先从公司的OA(B/S模式)系统下 打印指定内容的表单以及表单中的附件内容。这个问题可以这样分解：

1、抓包，得到OA对应的任务接口，然后利用python requests模拟post请求，获取所有的表单的URL并进行必要的去重处理；

2、打印OA表单的过程，需要浏览器在前台，这个时候可以结合selenium的driver.get(url)方法，打开每一个表单，同时解析网页内容，拿到所有附件的相关信息（名称、后缀、下载地址），利用requests再度保存这些附件至本地；

3、打开表单后，利用 win32api.keybd_event，模拟键盘快捷键“Ctrl + Shift + P”调出系统的打印窗口；

4、选中“PDF打印机”，需要电脑中有“Microsoft Print to Pdf”或者“Foxit Reader PDF Printer”等；

5、利用pywin32中的相关方法，驱动打印过程，将每个OA表单（网页）打印成PDF文件并格式化命名＆存储，与前面的附件内容存储到同一个文件夹；

６、附件文件和OA生成的PDF文件均格式化存储，用OA单号作为文件名的一部分，将两者关联起来；

７、将本地对应文件夹的所有内容有序推送给打印机，指定打印机为某一台网络打印机。同时要确保打印过程中，不乱序；

针对步骤3，可以自定义函数来实现：

#键盘按下
def key_down(keyname):
    win32api.keybd_event(vk_code[keyname],0,0,0)

#键盘抬起
def key_up(key_name):
    win32api.keybd_event(vk_code[key_name],0,win32con.KEYEVENTF_KEYUP,0)

#按键组合操作
def simulate_three_key(firstkey,sencondkey,lastkey):
    key_down(firstkey)
    key_down(sencondkey)
    key_down(lastkey)
    key_up(lastkey)
    key_up(sencondkey)
    key_up(firstkey)
#按键组合操作
def simulate_two_key(firstkey,sencondkey):
    key_down(firstkey)
    key_down(sencondkey)
    key_up(sencondkey)
    key_up(firstkey)

然后利用　simulate_three_key('ctrl',"shift",'p') 即可呼出系统的默认打印窗口：

　　那么步骤４，也就是上图的打印窗口，如何选中某一个打印机呢？直接利用win32gui.SendMessage

来选中某个打印机是非常困难的。一种可行的方法是，利用pywin32下的win32print模块，也就是本文的重点。

比如，用下面的代码可以遍历并获取到当前计算机的所有打印机信息：

for it in win32print.EnumPrinters(6):
    print(it[1])

我们甚至可以知道某台打印机的当前状态，假定某台打印机名为printerName，则可以这样获取打印机状态：

hPrinter = win32print.OpenPrinter (printerName)
dic = hex(win32print.GetPrinter(hPrinter,2)['Status'])
if dic[-2]=="8":
    print("The printer is offline.")
if dic[-5]=="4":
   print("The printer is out of toner.")
elif dic[-5]=="2":
   print("The printer is low on toner.") 

Printer status name/value	Description
PRINTER_STATUS_BUSY 0x00000200	The printer is busy.
PRINTER_STATUS_DOOR_OPEN 0x00400000	The printer door is open.
PRINTER_STATUS_ERROR 0x00000002	The printer is in an error state.
PRINTER_STATUS_INITIALIZING 0x00008000	The printer is initializing.
PRINTER_STATUS_IO_ACTIVE 0x00000100	The printer is in an active input or output state.
PRINTER_STATUS_MANUAL_FEED 0x00000020	The printer is in a manual feed state.
PRINTER_STATUS_NOT_AVAILABLE 0x00001000	The printer is not available for printing.
PRINTER_STATUS_NO_TONER 0x00040000	The printer is out of toner.
PRINTER_STATUS_OFFLINE 0x00000080	The printer is offline.
PRINTER_STATUS_OUTPUT_BIN_FULL 0x00000800	The printer's output bin is full.
PRINTER_STATUS_OUT_OF_MEMORY 0x00200000	The printer has run out of memory.
PRINTER_STATUS_PAGE_PUNT 0x00080000	The printer cannot print the current page.
PRINTER_STATUS_PAPER_JAM 0x00000008	Paper is stuck in the printer.
PRINTER_STATUS_PAPER_OUT 0x00000010	The printer is out of paper.
PRINTER_STATUS_PAPER_PROBLEM 0x00000040	The printer has an unspecified paper problem.
PRINTER_STATUS_PAUSED 0x00000001	The printer is paused.
PRINTER_STATUS_PENDING_DELETION 0x00000004	The printer is being deleted as a result of a client's call to RpcDeletePrinter. No new jobs can be submitted on existing printer objects for that printer.
PRINTER_STATUS_POWER_SAVE 0x01000000	The printer is in power-save mode.<182>
PRINTER_STATUS_PRINTING 0x00000400	The printer is printing.
PRINTER_STATUS_PROCESSING 0x00004000	The printer is processing a print job.
PRINTER_STATUS_SERVER_OFFLINE 0x02000000	The printer is offline.<183>
PRINTER_STATUS_SERVER_UNKNOWN 0x00800000	The printer status is unknown.<184>
PRINTER_STATUS_TONER_LOW 0x00020000	The printer is low on toner.
PRINTER_STATUS_USER_INTERVENTION 0x00100000	The printer has an error that requires the user to do something.
PRINTER_STATUS_WAITING 0x00002000	The printer is waiting.
PRINTER_STATUS_WARMING_UP 0x00010000	The printer is warming up.

更多的打印机接口信息，可查询微软的开发文档：https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rprn/1625e9d9-29e4-48f4-b83d-3bd0fdaea787?redirectedfrom=MSDN

我们也可以得到当前默认的打印机，设置默认打印机：

currentPrinter=win32print.GetDefaultPrinterW()
win32print.SetDefaultPrinterW(printer)

 我们利用上面两个函数，可以先得到系统当前的打印机，用变量存储后，再设置默认打印机至 PDF打印机，待执行完所有任务后，再设置默认打印机为用户一开始的默认打印机，整个过程用户不需要更多的干预；

　　重点说下步骤7：我们需要以OA表单+附件的形式，逐一给打印机分配任务，且不能乱序：

如果附件是图片性质，我们可以结合Pillow库来处理，示例代码如下：

import win32print
import win32ui
from PIL import Image, ImageWin


# Constants for GetDeviceCaps
#
#
# HORZRES / VERTRES = printable area
#
HORZRES = 8
VERTRES = 10
#
# LOGPIXELS = dots per inch
#
LOGPIXELSX = 88
LOGPIXELSY = 90
#
# PHYSICALWIDTH/HEIGHT = total area
#
PHYSICALWIDTH = 110
PHYSICALHEIGHT = 111
#
# PHYSICALOFFSETX/Y = left / top margin
#
PHYSICALOFFSETX = 112
PHYSICALOFFSETY = 113

def print_image(file_name):
 
    printer_name = win32print.GetDefaultPrinterW() # 获得默认打印机
    
    #
    # You can only write a Device-independent bitmap
    # directly to a Windows device context; therefore
    # we need (for ease) to use the Python Imaging
    # Library to manipulate the image.
    #
    # Create a device context from a named printer
    # and assess the printable size of the paper.
    #
    hDC = win32ui.CreateDC ()
    hDC.CreatePrinterDC (printer_name)
    printable_area = hDC.GetDeviceCaps (HORZRES), hDC.GetDeviceCaps (VERTRES)
    printer_size = hDC.GetDeviceCaps (PHYSICALWIDTH), hDC.GetDeviceCaps (PHYSICALHEIGHT)
    printer_margins = hDC.GetDeviceCaps (PHYSICALOFFSETX), hDC.GetDeviceCaps (PHYSICALOFFSETY)
    
    #
    # Open the image, rotate it if it's wider than
    # it is high, and work out how much to multiply
    # each pixel by to get it as big as possible on
    # the page without distorting.
    #
    bmp = Image.open (file_name)
    # bmp = bmp.rotate (90)
    # bmp.save("test1.png")
    if bmp.size[0] > bmp.size[1]:
        # bmp = bmp.rotate (90)
        bmp=bmp.transpose(Image.ROTATE_90)
    
    ratios = [1.0 * printable_area[0] / bmp.size[0], 1.0 * printable_area[1] / bmp.size[1]]
    scale = min (ratios)*0.85 #这个0.85的系数是不希望图片被打印太大，缺少margin，不方便文档的装订
    file_name=file_name.split("\")[-1] #这一步是为了提取fullpath中的filename部分
    
    #
    # Start the print job, and draw the bitmap to
    # the printer device at the scaled size.
    #
    hDC.StartDoc (file_name)
    hDC.StartPage ()
    
    dib = ImageWin.Dib (bmp)
    scaled_width, scaled_height = [int (scale * i) for i in bmp.size]
    x1 = int ((printer_size[0] - scaled_width) / 2)
    y1 = int ((printer_size[1] - scaled_height) / 2)
    x2 = x1 + scaled_width
    y2 = y1 + scaled_height
    dib.draw (hDC.GetHandleOutput (), (x1, y1, x2, y2))
    
    hDC.EndPage ()
    hDC.EndDoc ()
    hDC.DeleteDC ()

需要强调的是，如果我们对图片进行后台旋转90度时，一定要用transpose(Image.ROTATE_90)，不要使用 rotate (90)，否则打印的图片很有可能显示不完整，且有黑边；

具体的transpose用法见Pillow官网文档：

 如果我们要打印的任务是PDF或者其他office类型的文档，可以利用win32api.ShellExecute方法，示例如下：

def printer_loading(filename):
    # open (filename, "r")
    currentPrinter=win32print.GetDefaultPrinterW()
    win32api.ShellExecute (0,"print",filename,'/d:"%s"' % currentPrinter,".",0)

　　该方法有一个缺陷，win32api.ShellExecute 会在指令发出后，立即返回值，而不是等打印任务真正传输到打印机后再返回。这就意味着，附件中的图片用win32ui的方法走后台已经传输给打印机，而PDF等其他文件可能还没及时发送给打印机，造成打印任务乱序。

可行的解决方法是，利用win32print.EnumJobs，定时获取打印机当前的任务队列，确保队列中出现刚推送的任务后，再来推送下一个打印任务。示例如下：

handle = win32print.OpenPrinter(printer_name).handle

tasks=win32print.EnumJobs(handle,0, -1, 1)

for task in tasks:

    taskName=task["pDocument"]

由于打印任务是动态增减的，每次得到的tasks可能都不同，且由于打印机可能有很多人共同使用，不能保证某个用户的某次打印任务一定会出现在打印队列的最上方。所以要尽可能拿到所有的任务；

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至此，这个项目中的难点都逐一有了解决方案，希望小爬以上的思路，对喜欢自动化的你，能有所借鉴~~