Pillow/Tests/test_imagewin_pointers.py

from helper import unittest, PillowTestCase, hopper
from PIL import Image, ImageWin

import sys
import ctypes
from io import BytesIO

# see https://github.com/python-pillow/Pillow/pull/1431#issuecomment-144692652

if sys.platform.startswith('win32'):
    import ctypes.wintypes
    
    class BITMAPFILEHEADER(ctypes.Structure):
        _pack_ = 2
        _fields_ = [
            ('bfType', ctypes.wintypes.WORD),
            ('bfSize', ctypes.wintypes.DWORD),
            ('bfReserved1', ctypes.wintypes.WORD),
            ('bfReserved2', ctypes.wintypes.WORD),
            ('bfOffBits', ctypes.wintypes.DWORD),
        ]

    class BITMAPINFOHEADER(ctypes.Structure):
        _pack_ = 2
        _fields_ = [
            ('biSize', ctypes.wintypes.DWORD),
            ('biWidth', ctypes.wintypes.LONG),
            ('biHeight', ctypes.wintypes.LONG),
            ('biPlanes', ctypes.wintypes.WORD),
            ('biBitCount', ctypes.wintypes.WORD),
            ('biCompression', ctypes.wintypes.DWORD),
            ('biSizeImage', ctypes.wintypes.DWORD),
            ('biXPelsPerMeter', ctypes.wintypes.LONG),
            ('biYPelsPerMeter', ctypes.wintypes.LONG),
            ('biClrUsed', ctypes.wintypes.DWORD),
            ('biClrImportant', ctypes.wintypes.DWORD),
        ]

    BI_RGB = 0
    DIB_RGB_COLORS = 0

    memcpy = ctypes.cdll.msvcrt.memcpy
    memcpy.argtypes = [ ctypes.c_void_p, ctypes.c_void_p, ctypes.c_size_t ]

    CreateCompatibleDC = ctypes.windll.gdi32.CreateCompatibleDC
    CreateCompatibleDC.argtypes = [ ctypes.wintypes.HDC ]
    CreateCompatibleDC.restype = ctypes.wintypes.HDC

    DeleteDC = ctypes.windll.gdi32.DeleteDC
    DeleteDC.argtypes = [ ctypes.wintypes.HDC ]

    SelectObject = ctypes.windll.gdi32.SelectObject
    SelectObject.argtypes = [ ctypes.wintypes.HDC, ctypes.wintypes.HGDIOBJ ]
    SelectObject.restype = ctypes.wintypes.HGDIOBJ

    DeleteObject = ctypes.windll.gdi32.DeleteObject
    DeleteObject.argtypes = [ ctypes.wintypes.HGDIOBJ ]

    CreateDIBSection = ctypes.windll.gdi32.CreateDIBSection
    CreateDIBSection.argtypes = [ ctypes.wintypes.HDC, ctypes.c_void_p, ctypes.c_uint, ctypes.POINTER(ctypes.c_void_p), ctypes.wintypes.HANDLE, ctypes.wintypes.DWORD ]
    CreateDIBSection.restype = ctypes.wintypes.HBITMAP


    def serialize_dib(bi, pixels):
        bf = BITMAPFILEHEADER()
        bf.bfType = 0x4d42
        bf.bfOffBits = ctypes.sizeof(bf) + bi.biSize
        bf.bfSize = bf.bfOffBits + bi.biSizeImage
        bf.bfReserved1 = bf.bfReserved2 = 0

        buf = (ctypes.c_byte * bf.bfSize)()
        bp = ctypes.addressof(buf)
        memcpy(bp, ctypes.byref(bf), ctypes.sizeof(bf))
        memcpy(bp + ctypes.sizeof(bf), ctypes.byref(bi), bi.biSize)
        memcpy(bp + bf.bfOffBits, pixels, bi.biSizeImage)
        return bytearray(buf)

    class TestImageWinPointers(PillowTestCase):
        def test_pointer(self):
            im = hopper()
            (width, height) =im.size
            opath = self.tempfile('temp.png')
            imdib = ImageWin.Dib(im)

            hdr = BITMAPINFOHEADER()
            hdr.biSize = ctypes.sizeof(hdr)
            hdr.biWidth = width
            hdr.biHeight = height
            hdr.biPlanes = 1
            hdr.biBitCount = 32
            hdr.biCompression = BI_RGB
            hdr.biSizeImage = width * height * 4
            hdr.biClrUsed = 0
            hdr.biClrImportant = 0

            hdc = CreateCompatibleDC(None)
            #print('hdc:',hex(hdc))
            pixels = ctypes.c_void_p()
            dib = CreateDIBSection(hdc, ctypes.byref(hdr), DIB_RGB_COLORS, ctypes.byref(pixels), None, 0)
            SelectObject(hdc, dib)

            imdib.expose(hdc)
            bitmap = serialize_dib(hdr, pixels)
            DeleteObject(dib)
            DeleteDC(hdc)

            reloaded = Image.open(BytesIO(bitmap)).save(opath)

if __name__ == '__main__':
    unittest.main()