pygame image transformation: scaling, rotation, mirroring

function list

Pygame's transform encapsulates some basic image processing functions, the list is as follows

function	Function
flip	Mirror
scale	Scale to new resolution
scale_by	Scale by factor
scale2x	Professional image multiplier
rotate	rotate
rotozoom	Zoom and rotate
smoothscale	Smooth zoom
smoothscale_by	Smooth scaling to new resolutions
chop	Get a copy of the image with the inner areas removed
laplacian	edge search
average_surfaces	Averaging multiple images
average_color	Image color mean
grayscale	Grayscale
threshold	The number of pixels within a certain threshold

Image display

In order to demonstrate the effects of these functions, first make a function to display images through pygame

import pygame

def showImg(img):
    pygame.init()
    rect = img.get_rect()
    screen = pygame.display.set_mode((rect.width, rect.height))
    while True:
        for e in pygame.event.get():
            if e.type==pygame.QUIT:
                pygame.quit()
                return
        screen.blit(img, rect)
        pygame.display.flip()


ball = pygame.image.load("intro_ball.gif")
showImg(ball)

flip

Flip is used for flipping. In addition to the input image, there are two Boolean parameters, which are used to control the horizontal and vertical directions respectively. True means flipping, and False means not flipping.

import pygame.transform as pt
xFlip = pt.flip(ball, True, False)
yFlip = pt.flip(ball, False, True)
xyFlip = pt.flip(ball, True, True)

The effects are as follows

Zoom

Compared with mirroring, zooming is obviously a more common operation in games. In the transform module, two scaling solutions are provided

• scale(surface, size, dest_surface=None)
• scale_by(surface, factor, dest_surface=None)

Among them, scale scales the original image to the given size; scale_by scales the image according to the given factor. If factor is a number, then the same scaling will be performed in both directions. If A tuple, such as $(3,4)$, then scale the two dimensions by 3 times and 4 times respectively. Examples are as follows

xScale = pt.scale_by(ball, (2,1))
yScale = pt.scale(ball, (111,222))

In addition, smoothscale and smoothscale_by perform bilateral filtering and smoothing on the basis of scaling, making the scaling look more natural.

rotate

The image can be rotated through rotate. There are two input parameters, namely the image to be rotated and the rotation angle. This function can be seamlessly inserted into the previous flat tossing motion, that is, the ball will have a spin when it is flat tossed. The example is as follows

code show as below

import time

pygame.init()

size = width, height = 640, 320
speed = [10, 0]

screen = pygame.display.set_mode(size)

ball = pygame.image.load("intro_ball.gif")
rect = ball.get_rect()

th = 0
while True:
    if pygame.QUIT in [e.type for e in pygame.event.get()]:
        break
    time.sleep(0.02)
    rect = rect.move(speed)
    if rect.right>width:
        speed = [10, 0]
        rect = ball.get_rect()
    if rect.bottom>height:
        speed[1] = -speed[1]
    speed[1] += 1
    th += 5
    screen.fill("black")
    screen.blit(pt.rotate(ball, th), rect)
    pygame.display.flip()

pygame.quit()