Python 始终发生blit的无效目标

我正在使用pygame编程一个游戏引擎，这样我就可以开始构建psuedo-3d游戏，但是，当我尝试运行它时，我总是遇到这个错误

Invalid destination position for blit.

我试过用蛮力强迫所有的位置，但还是一无所获。 这是我的密码：

main.py:
import engine

cool = engine.OBJECT("data/cool.png", 600, 300, 10)

while True:
    if engine.events() == "up":
        engine.camera.zv = 1
    if engine.events() == "keyup":
        engine.camera.zv = 0
    if engine.events() == "quit":
        engine.end()
    cool.update()
    engine.draw()
    engine.refresh(engine.WHITE)

这是engine.py

engine.py:
import pygame, time, math, random, os

random.seed(time.time())

BLACK    = (   0,   0,   0)
WHITE    = ( 255, 255, 255)
GREEN    = (   0, 255,   0)
RED      = ( 255,   0,   0)
BLUE     = (   0,   0, 255)
PI       = 3.141592653
size     = (1200, 600)
done     = False
clock    = pygame.time.Clock()
screen   = pygame.display.set_mode(size)
pygame.display.set_caption("ENGINE")

class CAMERA(object):
    def __init__(self, image, iresize0, iresize1, xpos, ypos, zpos):
        self.x = xpos
        self.y = ypos
        self.z = zpos
        self.xv = 0
        self.yv = 0
        self.zv = 0
        if not image == "":
            self.image = pygame.image.load(os.path.join(image))
            self.image = pygame.transfrom.scale(self.image, (iresize0, iresize1))
            self.image.convert()

camera = CAMERA("", 0, 0, 0, 0, 0)

class OBJECT(object):
    global camera
    def __init__(self, image, xpos, ypos, zpos):
        self.x = xpos
        self.y = ypos
        self.z = zpos
        self.image = pygame.image.load(os.path.join(image))
        self.image.convert()
    def update(self):
        global camera
        self.x = (self.x) + camera.xv
        self.y = (self.y) + camera.yv
        self.z = (self.z*camera.z) + camera.zv
        if self.z > 0:
            self.image = pygame.image.load(os.path.join(image))
            self.image = pygame.transform.scale(self.image, int(self.z), int(self.z))
            self.image.convert()

def draw(img, pos):
    global screen
    screen.blit(img, pos)

def events():
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            return 'quit'
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                return 'left'
            if event.key == pygame.K_RIGHT:
                return 'right'
            if event.key == pygame.K_UP:
                return 'up'
            if event.key == pygame.K_DOWN:
                return 'down'
            if event.key == pygame.K_a:
                return 'a'
            if event.key == pygame.K_b:
                return 'b'
            if event.key == pygame.K_c:
                return 'c'
            if event.key == pygame.K_d:
                return 'd'
            if event.key == pygame.K_e:
                return 'e'
            if event.key == pygame.K_f:
                return 'f'
            if event.key == pygame.K_g:
                return 'g'
            if event.key == pygame.K_h:
                return 'h'
            if event.key == pygame.K_i:
                return 'i'
            if event.key == pygame.K_j:
                return 'j'
            if event.key == pygame.K_k:
                return 'k'
            if event.key == pygame.K_l:
                return 'l'
            if event.key == pygame.K_m:
                return 'm'
            if event.key == pygame.K_n:
                return 'n'
            if event.key == pygame.K_o:
                return 'o'
            if event.key == pygame.K_p:
                return 'p'
            if event.key == pygame.K_q:
                return 'q'
            if event.key == pygame.K_r:
                return 'r'
            if event.key == pygame.K_s:
                return 's'
            if event.key == pygame.K_t:
                return 't'
            if event.key == pygame.K_u:
                return 'u'
            if event.key == pygame.K_v:
                return 'v'
            if event.key == pygame.K_w:
                return 'w'
            if event.key == pygame.K_x:
                return 'x'
            if event.key == pygame.K_y:
                return 'y'
            if event.key == pygame.K_z:
                return 'z'
        if event.type == pygame.KEYUP:
            return 'keyup'

def refresh(backcolor):
    global clock, screen
    pygame.display.flip()
    clock.tick(60)
    screen.fill(backcolor)

def end():
    pygame.quit()

我先谢谢你。

---

更多详细信息

您试图在错误的位置“闪电”

确保使用正确的参数调用此函数

def draw(img, pos):
    global screen
    screen.blit(img, pos)

---

我看不到您在哪里调用draw函数？哦，对不起，我是在cool.updatebut draw下调用的。draw需要2个参数，而您没有在引擎中提供这些参数。draw调用？