python：使用Windows API渲染TTF字体文本

Question

有没有一个完整的例子，能从头到尾展示如何打开一个特定的.ttf字体文件，并用这个字体渲染一些文字，最后在内存中得到一个位图，使用的是原生的Windows API？我现在正在努力学习Windows API，所以我和StackOverflow上的其他人之间的竞争很激烈。

Answer 1

这是针对Python 3的更新版本，来自被接受的答案（完全归功于@Claudiu）。我用“Segoe UI”作为例子，来展示我们如何完美匹配Windows的原生用户界面：

import ctypes, struct, win32con, win32gui, win32ui, PIL.Image

def native_bmp_to_pil(hdc, bitmap_handle, width, height):
    bmpheader = struct.pack("LHHHH", struct.calcsize("LHHHH"), width, height, 1, 24)
    c_bmpheader = ctypes.c_buffer(bmpheader)
    c_bits = ctypes.c_buffer(b" " * (height * ((width*3 + 3) & -4)))
    res = ctypes.windll.gdi32.GetDIBits(hdc, bitmap_handle, 0, height, c_bits, c_bmpheader, win32con.DIB_RGB_COLORS)
    if not res:
        raise IOError("native_bmp_to_pil failed: GetDIBits")
    im = PIL.Image.frombuffer("RGB", (width, height), c_bits, "raw", "BGR", (width*3 + 3) & -4, -1)
    return im    

class Win32Font:
    def __init__(self, name, height, weight=win32con.FW_NORMAL, italic=False, underline=False):
        self.font = win32ui.CreateFont({'name': name, 'height': height, 'weight': weight, 'italic': italic, 'underline': underline})
        self.desktopHwnd = win32gui.GetDesktopWindow()
        self.desktopDC = win32gui.GetWindowDC(self.desktopHwnd)
        self.mfcDC = win32ui.CreateDCFromHandle(self.desktopDC)
        self.drawDC = self.mfcDC.CreateCompatibleDC()
        self.drawDC.SelectObject(self.font)

    def renderText(self, text):
        self.drawDC.SetTextColor(0)
        w,h = self.drawDC.GetTextExtent(text)
        saveBitMap = win32ui.CreateBitmap()
        saveBitMap.CreateCompatibleBitmap(self.mfcDC, w, h)        
        self.drawDC.SelectObject(saveBitMap)
        self.drawDC.DrawText(text, (0, 0, w, h), win32con.DT_LEFT)
        im = native_bmp_to_pil(self.drawDC.GetSafeHdc(), saveBitMap.GetHandle(), w, h)
        win32gui.DeleteObject(saveBitMap.GetHandle())
        return im

    def __del__(self):
        self.mfcDC.DeleteDC()
        self.drawDC.DeleteDC()
        win32gui.ReleaseDC(self.desktopHwnd, self.desktopDC)
        win32gui.DeleteObject(self.font.GetSafeHandle())

f = Win32Font("Segoe UI", 15)
im = f.renderText("Hello World")
im.save("test.png")

Answer 2

完成了字体渲染的工作（需要用到PyWin32库）：

import ctypes
import struct
import win32con
import win32gui
import win32ui

from PIL import Image


def RGB(r, g, b):    
    return r | (g << 8) | (b << 16)

def native_bmp_to_pil(hdc, bitmap_handle, width, height):
    bmpheader = struct.pack("LHHHH", struct.calcsize("LHHHH"),
                            width, height, 1, 24) #w,h, planes=1, bitcount)
    c_bmpheader = ctypes.c_buffer(bmpheader)

    #3 bytes per pixel, pad lines to 4 bytes    
    c_bits = ctypes.c_buffer(" " * (height * ((width*3 + 3) & -4)))

    res = ctypes.windll.gdi32.GetDIBits(
        hdc, bitmap_handle, 0, height,
        c_bits, c_bmpheader,
        win32con.DIB_RGB_COLORS)
    if not res:
        raise IOError("native_bmp_to_pil failed: GetDIBits")

    im = Image.frombuffer(
        "RGB", (width, height), c_bits,
        "raw", "BGR", (width*3 + 3) & -4, -1)
    return im    


class Win32Font:
    def __init__(self, name, height, weight=win32con.FW_NORMAL,
                 italic=False, underline=False):
        self.font = win32ui.CreateFont({
            'name': name, 'height': height,
            'weight': weight, 'italic': italic, 'underline': underline})

        #create a compatible DC we can use to draw:
        self.desktopHwnd = win32gui.GetDesktopWindow()
        self.desktopDC = win32gui.GetWindowDC(self.desktopHwnd)
        self.mfcDC = win32ui.CreateDCFromHandle(self.desktopDC)         
        self.drawDC = self.mfcDC.CreateCompatibleDC()

        #initialize it
        self.drawDC.SelectObject(self.font)

    def renderText(self, text):
        """render text to a PIL image using the windows API."""
        self.drawDC.SetTextColor(RGB(255,0,0))

        #create the compatible bitmap:
        w,h = self.drawDC.GetTextExtent(text)
        
        saveBitMap = win32ui.CreateBitmap()
        saveBitMap.CreateCompatibleBitmap(self.mfcDC, w, h)        
        self.drawDC.SelectObject(saveBitMap)

        #draw it
        self.drawDC.DrawText(text, (0, 0, w, h), win32con.DT_LEFT)

        #convert to PIL image
        im = native_bmp_to_pil(self.drawDC.GetSafeHdc(), saveBitMap.GetHandle(), w, h)

        #clean-up
        win32gui.DeleteObject(saveBitMap.GetHandle())

        return im        

    def __del__(self):
        self.mfcDC.DeleteDC()
        self.drawDC.DeleteDC()
        win32gui.ReleaseDC(self.desktopHwnd, self.desktopDC)
        win32gui.DeleteObject(self.font.GetSafeHandle())

    def __del__(self):
        win32gui.DeleteObject(self.font.GetSafeHandle())

使用方法：

>>> f = Win32Font("Arial", 15)
>>> im = f.renderText("this is just a test")
>>> im.save("c:/hope.png")

结果：

太棒了！！！

要渲染一个特定的.ttf文件，我还需要进一步探索。

更新：更新了计算位图大小的功能：