Converting Pygame image gives an error

Question

I'm learning Pygame by making simple games with it. But my game is very laggy and I've learned that it could be because pygame is converting the .png image everytime it blits to the screen.

So I tried to use convert() to load the image. But it gives me an error. Made some research but no answer could help me even though I've tested some.

my code:

import pygame
import os, random


class Item:
    def __init__(self):

        self.image = Context.load_image("item.png")

        self.X = random.randint(0, Context.resolution[1] - 200) 
        self.Y = 0

        self.dY = 10


class Basket:
    def __init__(self):
        self.image = Context.load_image("catcher.png")

        self.X = Context.resolution[0] / 2
        self.Y = Context.resolution[1] - 200    

        self.vel = 30.
        self.dX  = self.dY = 0

def action(self, event):
    if event.type == pygame.KEYDOWN:
        if event.key == pygame.K_a:
            self.dX = -self.vel
        elif event.key == pygame.K_d:
            self.dX = self.vel

    elif event.type == pygame.KEYUP:
        self.dX = 0


class Context:
    resolution      = (1600, 900)

    dir_resources   = "resources/"

    def __init__(self):
        self.fps = 60
        self.background_theme = self.load_image("background.png")

    @staticmethod
    def load_image(image_name):
        path = Context.dir_resources + image_name
        # ERROR HAPPENS HERE! If I take ".convert()" off, the game runs but laggy
        return pygame.image.load(os.path.join(path)).convert() 


class Game:
    score = 0

def __init__(self):
    self.game_on = True

    self.context = Context()
    self.basket  = Basket()

    self.screen = pygame.display.set_mode(self.context.resolution, pygame.HWSURFACE | pygame.DOUBLEBUF)
    self.fps    = self.context.fps
    self.clock  = pygame.time.Clock()

    self.tshirt = Item()

def event_loop(self):
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            self.game_on = False

        self.basket.action(event)

def update(self):   
    self.basket.X = self.basket.X + self.basket.dX
    self.tshirt.Y = self.tshirt.Y + self.tshirt.dY

def draw(self):
    self.screen.blit(self.context.background_theme, (0, 0))

    self.screen.blit(self.basket.image, (self.basket.X, self.basket.Y))
    self.screen.blit(self.tshirt.image, (self.tshirt.X, self.tshirt.Y))

    pygame.display.flip()

def run(self):
    while self.game_on:
        self.event_loop()
        self.update()
        self.draw()

        pygame.display.update()
        self.clock.tick(self.fps)

def main():
    pygame.init()

    game = Game()
    game.run()

    pygame.quit()

if __name__ == '__main__':
    main()

here is the error:

Traceback (most recent call last):
  File "/me/tmvaz/PycharmProjects/Game/__main__.py", line 105, in <module>
    main()
  File "/home/me/PycharmProjects/Game/__main__.py", line 98, in main
    game = Game()
  File "/home/me/PycharmProjects/Game/__main__.py", line 57, in __init__
    self.context = Context()
  File "/home/me/PycharmProjects/Game/__main__.py", line 42, in __init__
    self.background_theme = self.load_image("background.png")
  File "/home/me/PycharmProjects/Game/__main__.py", line 47, in load_image
    return pygame.image.load(os.path.join(path)).convert()
pygame.error: No video mode has been set

Process finished with exit code 1

I'm using Linux, Lubuntu if that could be helpfull.

Answer 1

You have to call pygame.display.set_mode before you call the convert or convert_alpha methods. So I'd just move this line to the top of the program:

pygame.init()
screen = pygame.display.set_mode(resolution, pygame.HWSURFACE | pygame.DOUBLEBUF)

You can pass the screen variable to the Game object when you instantiate it and then assign it to self.screen.