如何使用光泽库在屏幕上移动自定义图像

问：

我正在尝试构建一个简单的光泽游戏，该游戏使用 BMP 文件作为精灵，这些精灵将在加载后进行动画和移动。我正在尝试使用动画或模拟功能让其中一些图像移动。

simulate 的参数之一是类型 （model -> Picture）（即采用用户定义的数据类型存储游戏状态并返回 Picture 的函数），而通常用于加载文件的 loadBMP 函数是 loadBMP ：： FilePath -> IO Picture。

很难掌握我应该在更高级别上做什么才能让图像移动，特别是考虑到 loadBMP 会返回 Picture IO 而不是 Picture。有什么想法吗？对不起，如果这还不够具体。

module Main(main) where

import Graphics.Gloss
import System.IO  
import Control.Monad
import Graphics.Gloss.Data.ViewPort

data GameState = State{ 
      boardpic::Picture
    , ballpic :: Picture
    , ballCoords :: (Float, Float)  
    , ballSpeed :: (Float, Float) 
    , paddle1pic::Picture  
    , p1Coords :: (Float, Float)
    , paddle2pic::Picture
    , p2Coords:: (Float,Float)
    , paused::Bool
    , turnscore::Integer                                  
    } deriving (Show) 

moveBall time state = state {ballCoords = (xnew, ynew)} 
    where
    (xposbefore, yposbefore) = ballCoords state 
    (xspeed, yspeed) = ballSpeed state
    (xnew, ynew) = (xposbefore + xspeed*time, yposbefore+xspeed*time)

render::GameState->Picture
render state =  
  pictures[board, 
           paddle1, 
           paddle2,
           ball]
  where
    board = boardpic state
    ball = translate 0 0 $ ballpic state
    paddle1 = translate (-300) 0 $ paddle1pic state
    paddle2 = translate 300 0 $ paddle2pic state  

--calculates running sum of score for the player from list 
score xs = tail.reverse $ foldl f [0] xs 
  where 
    f (y:ys) x = (x+y):y:ys
 
window :: Display
window = InWindow "SuperPong" (800, 800) (0,0)

background::Color
background = blue

fps :: Int
fps = 60
    
printState::GameState->IO ()
printState state = do
  putStrLn $ show $ boardpic state
  putStrLn $ show $ ballpic state
  putStrLn $ ("ball coordinates: ")++(show $ ballCoords state)
  putStrLn $ ("paddle1 coords:  " )++(show $ p1Coords state)
  putStrLn $ ("paddle2 coords: " )++(show $ p2Coords state)
  putStrLn $ ("paused or not: " ) ++ (show $ paused state)
  putStrLn $ ("score: " )++(show $ turnscore state)

--paddlecollision::

--outofbounds::

main :: IO ()
main = do
  pad1 <- loadBMP "paddle1.bmp"
  pad2 <- loadBMP "paddle2.bmp"
  board <- loadBMP "board.bmp"
  ball1 <- loadBMP "ball.bmp"

  let initstate = State{
    boardpic = board
  , ballpic = ball1
  , ballCoords = (-10, 10)
  , ballSpeed = (50, -50)
  , paddle1pic = pad1
  , p1Coords = (-300, 0)
  , paddle2pic = pad2
  , p2Coords = (300, 0)
  , paused = False
  , turnscore = 0
  }
    
  let update _ = moveBall 
  
  printState initstate
  let allpics = render initstate     

  simulate window background fps initstate render update

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