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--- en:part2:pygame:step008 [2010/01/24 14:17]
Horst JENS
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-^ [[:en:part2:step007| ← previous]] ^ [[en:part2:start| ↑ Overview]] ^ [[:en:part2:step009| → next ]] ^
-====== step 008 - loading images ======
-==== discussion ====
-=== loading images ===
-Using pre-fabricated images instead of painting all images yourself with the [[http://www.pygame.org/docs/ref/draw.html|pygame.draw - functions]] comes very handy. This example shows you how to load images into pygame. Note that in this example, the images must be in the same folder as the python program ! In this example, if pygame can not find the images, it will print an error message and use the image-drawing methods from the previous code example.
-=== catching file not found error ====
-This is done using the **try:** **except:** method.
-<code python>
-try:
-   #do something risky that may not work like loading files
-   #...
-except:
-   #do that if an error occurs inside the try block
-   #...
-# continue here if no error
-</code>
- Also see the official documentation:
-==== documentation ====
-  * python 2.x
-    * http://docs.python.org/reference/compound_stmts.html#the-try-statement
-  * python 3.x
-    * http://docs.python.org/3.1/reference/compound_stmts.html#the-try-statement
-==== additional resources ====
-Put those 2 graphic files in the same folder as **part2step008-loading-image.py** to make the program run correctly. If one or both of those files are not found you will see a brown and a blue circle instead:
-^ filename ^ preview / note  ^ file must be in folder ^ source / license ^
-| ::: | left-click to zoom to original size,\\ then right-click to download | <key>.</key>  means the same\\ folder as the program | ::: |
-| {{filename>babytux.png}} | {{:en:part2:babytux.png|Babytux graphic file (.png) with transparent border}} |  <key>.</key>   | wikimedia commons |
-| {{filename>background640x480_a.jpg}} | {{:en:part2:background640x480_a.jpg?150|background.jpg file}} \\  |  <key>.</key>  | Horst JENS / public domain |
-| {{:en:part2:part2step008.zip|}} | all files except the source code\\ in a zipped package | | |
-==== source code ====
-<code python| part2step008-loading-image.py>
-# -*- coding: utf-8 -*-
-"""
-part2step008-loading-image.py
-loading images from harddisk and using convert_alpha()
-This program try to load 2 image files from the harddisk. Both files must be in the
-same folder as the program itself. If the image files are not found, images are
-created by code instead and an error message is printed.
-Note that convert_alpha() is only necessary when the loaded image had
-a transparent color. Some .png and .gif files have this, but never .jpg files.
-"""
-import pygame
-pygame.init()
-screen=pygame.display.set_mode((640,480)) # try out larger values and see what happens !
-try:
-    background = pygame.image.load("background640x480_a.jpg")
-except:
-    print("Error: the image background640x480_a.jpg is not in this folder")
-    background = pygame.Surface(screen.get_size()) # create a pygame Surface
-    background.fill((255,255,255))                 # fill the background white
-    pygame.draw.circle(background, (50,50,0), (300,250), 200)   # draw circle
-try:
-    ball = pygame.image.load("babytux.png")
-except:
-    print("Error: the image babytux.png is not in this folder")
-    ball = pygame.Surface((50,50))     #create a new black surface
-    ball.set_colorkey((0,0,0))
-    pygame.draw.circle(ball, (0,0,255), (25,25),25) # paint blue circle
-#finally:
-background = background.convert()  # jpg can not have transparency
-ball = ball.convert_alpha()        # png image has transparent color
-ballx, bally = 550, 240            # start position of ball surface
-dx, dy  = 60, 60                   # ball speed in pixel per second !
-screen.blit(background, (0,0))     # blit background on screen (overwriting all)
-screen.blit(ball, (ballx, bally))  # blit the ball shape
-clock = pygame.time.Clock()        # create pygame clock object
-mainloop = True
-FPS = 60                           # desired max. framerate in frames per second.
-while mainloop:
-    milliseconds = clock.tick(FPS)  # milliseconds passed since last frame
-    seconds = milliseconds / 1000.0 # seconds passed since last frame
-    for event in pygame.event.get():
-        if event.type == pygame.QUIT:
-            mainloop = False # pygame window closed by user
-        elif event.type == pygame.KEYDOWN:
-            if event.key == pygame.K_ESCAPE:
-                mainloop = False # user pressed ESC
-    pygame.display.set_caption("[FPS]: %.2f X:%.1f Y:%.1f Speed"
-    " [pixel/sec] dx:%.2f dy:%.2f" % (clock.get_fps(), ballx, bally, dx, dy))
-    # only blit the part of the background where the ball was (cleanrect)
-    dirtyrect = background.subsurface((round(ballx,0),
-                round(bally,0), ball.get_width(), ball.get_height()))
-    # comment out the next line for a funny effect !
-    screen.blit(dirtyrect, (round(ballx,0), round(bally,0)))
-    #calculate new center of ball
-    ballx += dx * seconds # time based movement
-    bally += dy * seconds
-    # bounce ball if out of screen
-    if ballx < 0:
-        ballx = 0
-        dx *= -1
-    elif ballx + ball.get_width() > screen.get_width():
-        ballx = screen.get_width() - ball.get_width()
-        dx *= -1
-    if bally < 0:
-        bally = 0
-        dy *= -1
-    elif bally + ball.get_height() > screen.get_height():
-        bally = screen.get_height() - ball.get_height()
-        dy *= -1
-    # paint the ball
-    screen.blit(ball, (round(ballx,0), round(bally,0)))
-    pygame.display.flip()          # flip the screen 30 times a second                # flip the screen 30 (or FPS) times a second
-</code>
-^ [[:en:part2:step007| ← previous]] ^ [[en:part2:start| ↑ Overview]] ^ [[:en:part2:step009| → next ]] ^

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