01 Game Arch Pygame

1 Conclusion#

代码不用学，直接查就好

2 Pygame#

Python for writing video games
- Modules
- Install pip/conda install pygame

2.1 Example#

intro1.py
import pygame

pygame.init()

size = width, height = 1024, 768
speed = [3, 2]
black = (0, 0, 0)

screen = pygame.display.set_mode(size)
logo = pygame.image.load('new.jpg')
logo_width, logo_height = logo.get_size()
logo_x = logo_y = 0

running = True

while running:  
    for event in pygame.event.get():  
        if event.type == pygame.QUIT:  
            running = False  

    logo_x += speed[0]
    logo_y += speed[1]

    if logo_x < 0 or logo_x + logo_width > width:
        speed[0] = -speed[0]
    if logo_y < 0 or logo_y + logo_height > height:
        speed[1] = -speed[1]

    screen.fill(black)
    screen.blit(logo, (logo_x, logo_y))
    pygame.display.flip()

创建一个窗口，窗口内 new.jpg 在移动，接触到边反弹

3 Game Loop#

the common structure
- initialization
- a loop (while running)
  - check inputs, from user, network
  - upgrade game state, based on inputs
  - draw next frame, based on the state
philosophy: games need to be responsive

3.1 Frame#

one picture is rendered each time, which is a frame
FPS is usually an important design metric/goal

normal structure of a game
initialize_game()
while not done:
    *user_inputs, done = get_inputs()
    game_state = update_game_state(user_inputs)
    render_game(game_state)

3.2 Event Queue#

Pygame uses event queue to manage user inputs
- FIFO: first-in-first-out
- Event: an object representing sth. happening in the system
Each game loop, you must handle all the events in the queue
Pygame's event module has very extensive features for handling the even queue

3.2.1 Event Objects#

event_object.type
- KEYDOWN: key, mod(are shift, ctrl keys also pressed), unicode, scancode
- MOUSEBUTTONDOWN: pos(x, y of the cursor), button(which is clicked)
- VIDEORESIZE: size

Example event processing
def get_inputs()
    done = ledt = right = False
    for event in pygamme.event.get():
        if event.type == pygame.QUIT
            done = True
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_ESCAPE
                done = True
            elif event.key == pygame.K_RIGHT:
                right = True
            elif event.key == pygame.K_LEFT:
                left = True
    return (left, right, done)

4 Game Architecture#

Architecture is all about the structure of our code.
- components
- how they interact with each other

4.1 MVC: Model-View-Controller#

MVC is a common architectural style for GUI, web applications and games

4.1.1 Model#

Manages the data and operations on the data
Provides a well-defined interface to the data
- changes to the data structure don't require changes to the rest of the code
In web and many GUI apps, model is a database
Example: Chess Game
- Data: where are all pieces, which have been captured
- Operations: init, moving pieces, werid moves, scoring of captured pieces

4.1.2 View#

Provides a way to visualize the data
- frame, music, runble, etc.
Example: Chess Game
- 2D/3D/VR, phone/laptor/console views

4.1.3 Controller#

Maps input actions to model or view actions
- input actions: user input
- model actions: avatar moved left, opponent forfeits, spaceship explodes...
- view actions: window resized, menu button pressed, instant replay requested
Game customizations often result in different mappings for the controller
- WASD/arrow keys

4.1.4 Advice on MVC#

When programming, start with the model, how to store data and how are they controlled

4.2 Object-Orinted Model/View#

Another common style is having objects
- Pac-Man, Ghosts, fruit, the maze ...

4.2.1 Object#

Each object knows its own state and update rules, so is part of the model
A model component may still keep trach of all objects and tell them when to update

4.2.2 Draw#

Each object knows how to draw itself, so is part of view
- object.draw() is called by the view module

4.2.3 Conclusion#

You still have a model, which calls object.update()
You still have a view, which calls object.draw(), in correct order

5 Graphic Primitives#

Provides visual feedback
Provides guidance

5.1 Engine#

An engine provides some level of graphic algorithms to be embedded in your code

5.1.1 Digital Image#

array of pixels of colors
RGB/RGBA, A is for Alpha Channel

5.2 The Surface#

In Pygame, a surface is a place to draw
Special surface, the display surface, is visible to the user in game window
- {python}display_surface = pygame.display.set_mode((1024, 768))
Other surfaces can be created too
Commonly, have a background surface
- {python}background = pygame.Surface(display_surface.get_size())
- 每一帧先复制一遍 background 再开始绘图

5.2.1 Surface Operations#

set the color of single pixel{python}background.set_at((x, y), color)
get the color of single pixel {python}color = background.get_at(x, y)

draw_notepaper.py (naive version)
def draw(surface, size_x, size_y):
    blue = (0, 0, 200)
    red = (200, 0, 0)
    white = (255, 255, 255)

    # draw white background
    for x in range(size_x):
        for y in range(size_y):
            surface.set_at((x, y), white)

    # draw horizontal lines
    for y in range(60, size_y, 20):
        for x in range(size_x):
            surface.set_at((x, y), red)

    # draw a red vertical line in the left
    x = 25
    for y in range(0, size_y):
        surface.set_at((x, y), red)

5.3 `pygame.draw`#

TMBABW There must be a better way

draw_notepaper.py (better version)
def draw(surface, size_x, size_y):
    blue = (0, 0, 200)
    red = (200, 0, 0)
    white = (255, 255, 255)

    # draw white background
    surface.fill(white)

    # draw horizontal lines
    for y in range(60, size_y, 20):
        left_side = (0, y)
        right_side = (size_x, y)
        pygame.draw.line(surface, blue, left_size, right_side)

    # draw a red vertical line in the left
    pygame.draw.line(surface, red, (25, 0), (25, size_y))

{python}pygame.draw.arc(surface, color, rect, start_angle, stop_angle, width=1)
- rect 是一个 bounding box
- start_angle 和 stop_angle 是弧度制的
{python}pygame.draw.lines(surface, color, closed, points, width=1)
- 绘制一些直线，经过 points 列表里的所有 (x, y) 元组
- closed: bool，是否生成闭合图形
{python}pygame.draw.polygon(surface, color, points, width=1)
- 连接所有 (x, y) 点，并填充封闭空间
{python}pygame.draw.circle(surface, color, center, radius)

draw_python.py -- Draw the Python logo
surface.fill(white)
points = [(27, 50), (76, 50), (76, 45), (45, 45), (45, 26)]
pygame.draw.lines(surface, blue, False, points)
pygame.draw.arc(surface, blue, (45, 15, 61, 22), 0*radians, 180*radians)
pygame.draw.line(surface, blue, (106, 26), (106, 62))
pygame.draw.arc(surface, blue, (76, 47, 30, 30), 270*radians, 0*radians)
pygame.draw.line(surface, blue, (91, 76), (57 ,76))
pygame.draw.arc(surface, blue, (41, 76, 32, 32), 90*radians, 180*radians)
pygame.draw.line(surface, blue, (41, 92), (41, 110))
pygame.draw.line(surface, blue, (41,110), (27, 110))
pygame.draw.arc(surface, blue, (12,50,30, 60), 90*radians, 270*radians)
......

5.4 `pygame.rect`#

{python}pygame.Rect(x, y, width, height)
{python}pygame.Rect((x, y), (width, height))
Rect Methods

5.5 Using Rects with Draw#

{python}pygame.draw.rect(surface, color, rect, width=0)
{python}pygame.draw.ellipse(surface, color, rect, width=0)

Use rects for boxes, circles in draw_checherboard.py
rect = pygame.Rect(strip_size, strip_size, box_size, box_size)  # make rect for checkerboard box
color = black
for row in range(8):
    for col in range(8):
        pygame.draw.rect(surface, color, rect)  # draw the box
        if row in rows_with_pieces and color == black:
            circle_rect = rect.inflate(deflate, deflate)
            pygame.draw.ellipse(surface, white, circle_rect)   # draw ellipse in smaller box
        rect.move_ip(box_size + strip_size, 0)  # move rect to the next place in row
        if color == black:
            color = red
        else:
            color = black
    rect.move_ip(-8*(box_size + strip_size), box_size + strip_size)  # move rect to next row
    if color == black:
        color = red
    else: 
        color = black

6 Images and Blit#

使用 .png, .jpg, .gif 等图像代替绘制语句
Pygame supports PG, PNG, GIF + BMP, PCX, TGA, TIF, LBM, PBM, PPM and XPM formats

6.1 Image Load/Save#

{python}surface = pygame.image.load(filename)
{python}pygame.image.save(surface, filename)
{python}pygame.surface.convert()
- 能够修改 surface 的格式来 match display surface
- 最好对每个加载的 image 都使用，不然每次都要 convert

6.2 BLIT#

每个图像都是单独的 surface，但是需要在每个 loop 结尾绘制单个 display_surface
blit 能够复制粘贴图像

6.2.1 Pygame blit#

surface 对象具有这样的方法：{python}surface.blit(source, dest, area=None, special_flags=0)
- source 另一个 surface
- dest 是一个 (x, y) 坐标
- area 可以是一个 rect，来限制粘贴的范围

render mario
display_surface = pygame.display.set_mode(1200, 622)
background = pygame.image.load('mario_background.png').convert()
mario = pygame.image.load('mario_sprited.png').convert()
...
while not done:
    *user_inputs, done = get_inputs()
    ...
    jump_r = pygame.Rect(254, 13, 42, 49)
    display_surface.blit(background, (0, 0))
    display_surface.blit(mario, (390, 510), jump_r)
    pygame.display.flip()

6.2.2 Blit Optimizaiton#

使用 spacial_flags 参数加速处理过程，ADD, SUB, MULT, MIN, MAX

6.3 ColorKey#

用于将素材种的某种颜色当成透明，不覆写 display_surface 中的部分像素

render mario
display_surface = pygame.display.set_mode(1200, 622)
background = pygame.image.load('mario_background.png').convert()
mario = pygame.image.load('mario_sprited.png').convert()
white = mairo.get_at((0, 0))
mario.set_colorkey(white)
...
while not done:
    *user_inputs, done = get_inputs()
    ...
    jump_r = pygame.Rect(254, 13, 42, 49)
    display_surface.blit(background, (0, 0))
    display_surface.blit(mario, (390, 510), jump_r)
    pygame.display.flip()

6.4 Surface Transforms#

You can rotate / scale / chop / greyscale / ...
{python}pygame.transform.rotate(source_surface, angle) -> Surface

7 Conclusion#

Games are a part of human nature
Game architectures are important
Pygame engine is a library with lots of useful routines
- lines, colors, circles, images, ...
- events
- surfaces

Hint

其实 python 程序可读性都很强，完全不用记这些函数定义也能看懂

01 Game Arch Pygame

1 Conclusion#

2 Pygame#

2.1 Example#

3 Game Loop#

3.1 Frame#

3.2 Event Queue#

3.2.1 Event Objects#

4 Game Architecture#

4.1 MVC: Model-View-Controller#

4.1.1 Model#

4.1.2 View#

4.1.3 Controller#

4.1.4 Advice on MVC#

4.2 Object-Orinted Model/View#

4.2.1 Object#

4.2.2 Draw#

4.2.3 Conclusion#

5 Graphic Primitives#

5.1 Engine#

5.1.1 Digital Image#

5.2 The Surface#

5.2.1 Surface Operations#

5.3 pygame.draw#

5.4 pygame.rect#

5.5 Using Rects with Draw#

6 Images and Blit#

6.1 Image Load/Save#

6.2 BLIT#

6.2.1 Pygame blit#

6.2.2 Blit Optimizaiton#

6.3 ColorKey#

6.4 Surface Transforms#

7 Conclusion#

5.3 `pygame.draw`#

5.4 `pygame.rect`#