PySDL2问题与SDL_Surface / LP_SDL_Surface

Question

我用python 3.3和PySDL2 0.5运行win7。创建曲面时（无论使用哪种方法），我都会得到LP_SDL_Surface而不是SDL_Surface。LP_SDL_Surface缺少您期望的任何方法和属性。这是使用文档中示例代码的问题：

import os
os.environ["PYSDL2_DLL_PATH"] = os.path.dirname(os.path.abspath(__file__))

import sys
import ctypes
from sdl2 import *

def main():
    SDL_Init(SDL_INIT_VIDEO)
    window = SDL_CreateWindow(b"Hello World",
                              SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
                              592, 460, SDL_WINDOW_SHOWN)
    windowsurface = SDL_GetWindowSurface(window)

    image = SDL_LoadBMP(b"exampleimage.bmp")
    SDL_BlitSurface(image, None, windowsurface, None)
    print(image.h)

    SDL_UpdateWindowSurface(window)
    SDL_FreeSurface(image)

    running = True
    event = SDL_Event()
    while running:
        while SDL_PollEvent(ctypes.byref(event)) != 0:
            if event.type == SDL_QUIT:
                running = False
                break

    SDL_DestroyWindow(window)
    SDL_Quit()
    return 0

if __name__ == "__main__":
    sys.exit(main())

追溯为：

Traceback (most recent call last):
File "C:/.../test.py", line 35, in <module>
sys.exit(main())
File "C:/.../test.py", line 17, in main
print(image.h)
AttributeError: 'LP_SDL_Surface' object has no attribute 'h'

谷歌搜索“ LP_SDL_Surface”带来0（！）结果。

Answer 1

如果您使用较低级别的 SDL 方法（例如sdl2.SDL_LoadBMP），您将必须处理 ctypes 转换、引用（byref）和指针的取消引用（.contents、.value）。

因此，对于具体问题，正如您已经评论的那样，使用print(image.contents.h)就足够了。

然而，pysdl2 ( ) 提供了一些更高级别的类和方法sdl2.ext，如果需要的话，它们可以为您完成大部分转换。下面的代码无需接触 ctypes 即可实现相同的目标：

import os
os.environ["PYSDL2_DLL_PATH"] = os.path.dirname(os.path.abspath(__file__))

import sys
import sdl2
import sdl2.ext

def main():
    sdl2.ext.init()
    window = sdl2.ext.Window(
        title="Hello World!", size=(592, 460), flags=sdl2.SDL_WINDOW_SHOWN,
        position=(sdl2.SDL_WINDOWPOS_CENTERED, sdl2.SDL_WINDOWPOS_CENTERED))

    window.show()

    renderer = sdl2.ext.Renderer(window)
    factory = sdl2.ext.SpriteFactory(sdl2.ext.TEXTURE, renderer=renderer)
    spriterenderer = factory.create_sprite_render_system(window)

    image = factory.from_image("exampleimage.bmp")
    print(image.size[1])  # image.size = (w, h)

    running = True
    while running:
        for event in sdl2.ext.get_events():
            if event.type == sdl2.SDL_QUIT:
                running = False
                break
        spriterenderer.render(image)

    sdl2.ext.quit()
    return 0

if __name__ == '__main__':
    sys.exit(main())

它还利用纹理渲染，使用硬件加速，而不是表面位块传输（基于软件）。

最后，使用更高的级别，sdl2.ext您还可以实例化类（而不必自己编写一个全新的精灵类）sdl2.ext.sprite.TextureSprite，并实现一个h属性：

class TextureSprite(sdl2.ext.TextureSprite):

    @property
    def h(self):
        """The height of the TextureSprite."""
        return self.size[1]

    @property
    def w(self):
        """The width of the TextureSprite."""
        return self.size[0]