Rotating a rectangle (not image) in pygame
Question:
In pygame I use pygame.draw.rect(screen, color, rectangle) for all the rectangles in my program. I want to be able to rotate these rectangles to any angle. I have seen the following code to rotate IMAGES but my question is with RECTANGLES.
pygame.transform.rotate(image, angle)
But I am working with rectangles, I don’t have an image or “surface” that I can rotate. When I try to rotate a rectangle with
rect = pygame.draw.rect(screen, self.color, self.get_rectang())
rotatedRect = pygame.transform.rotate(rect, self.rotation)
screen.blit(rotatedRect)
This gives TypeError: must be pygame.Surface, not pygame.Rect on the line with .rotate()
My question is, how can I rotate a and display a RECTANGLE(x,y,w,h), not an image, in pygame.
The linked post that this is a “potential duplicate” of is not a duplicate. One answer explains about the consequences of rotating a rectangle and the other uses code for rotating an image.
Answers:
See the second answer here: Rotating a point about another point (2D)
I think rectangles can only be horiz or vertical in their oreintation. You need to define the corners and rotate them and then draw and fill between them.
The other way is to make a class
class myRect(pygame.Surface):
def __init__(self, parent, xpos, ypos, width, height):
super(myRect, self).__init__(width, height)
self.xpos = xpos
self.ypos = ypos
self.parent = parent
def update(self, parent):
parent.blit(self, (self.xpos, self.ypos))
def rotate(self, angle):
#(your rotation code goes here)
and use that instead, as then you will be able to rotate it using the transform function.
import pygame as py
# define constants
WIDTH = 500
HEIGHT = 500
FPS = 30
# define colors
BLACK = (0 , 0 , 0)
GREEN = (0 , 255 , 0)
# initialize pygame and create screen
py.init()
screen = py.display.set_mode((WIDTH , HEIGHT))
# for setting FPS
clock = py.time.Clock()
rot = 0
rot_speed = 2
# define a surface (RECTANGLE)
image_orig = py.Surface((100 , 100))
# for making transparent background while rotating an image
image_orig.set_colorkey(BLACK)
# fill the rectangle / surface with green color
image_orig.fill(GREEN)
# creating a copy of orignal image for smooth rotation
image = image_orig.copy()
image.set_colorkey(BLACK)
# define rect for placing the rectangle at the desired position
rect = image.get_rect()
rect.center = (WIDTH // 2 , HEIGHT // 2)
# keep rotating the rectangle until running is set to False
running = True
while running:
# set FPS
clock.tick(FPS)
# clear the screen every time before drawing new objects
screen.fill(BLACK)
# check for the exit
for event in py.event.get():
if event.type == py.QUIT:
running = False
# making a copy of the old center of the rectangle
old_center = rect.center
# defining angle of the rotation
rot = (rot + rot_speed) % 360
# rotating the orignal image
new_image = py.transform.rotate(image_orig , rot)
rect = new_image.get_rect()
# set the rotated rectangle to the old center
rect.center = old_center
# drawing the rotated rectangle to the screen
screen.blit(new_image , rect)
# flipping the display after drawing everything
py.display.flip()
py.quit()
a quick replacement of the base pygame function adding rotation:
def rectRotated( surface, color, pos, fill, border_radius, angle ):
"""
- angle in degree
"""
max_area = max(pos[2],pos[3])
s = pg.Surface((max_area,max_area))
s = s.convert_alpha()
s.fill((0,0,0,0))
pg.draw.rect(s, color,(0,0,pos[2],pos[3]),fill, border_radius=border_radius)
s = pygame.transform.rotate(s,angle)
surface.blit( s, (pos[0],pos[1]) )
a more complex version of the quick replacement, in which you can define an arbitrary rotation center point for your rectangle – even outside of it (tested in python3):
def rectRotated( surface, color, pos, fill, border_radius, rotation_angle, rotation_offset_center = (0,0), nAntialiasingRatio = 1 ):
"""
- rotation_angle: in degree
- rotation_offset_center: moving the center of the rotation: (-100,0) will turn the rectangle around a point 100 above center of the rectangle,
if (0,0) the rotation is at the center of the rectangle
- nAntialiasingRatio: set 1 for no antialising, 2/4/8 for better aliasing
"""
nRenderRatio = nAntialiasingRatio
sw = pos[2]+abs(rotation_offset_center[0])*2
sh = pos[3]+abs(rotation_offset_center[1])*2
surfcenterx = sw//2
surfcentery = sh//2
s = pg.Surface( (sw*nRenderRatio,sh*nRenderRatio) )
s = s.convert_alpha()
s.fill((0,0,0,0))
rw2=pos[2]//2 # halfwidth of rectangle
rh2=pos[3]//2
pg.draw.rect( s, color, ((surfcenterx-rw2-rotation_offset_center[0])*nRenderRatio,(surfcentery-rh2-rotation_offset_center[1])*nRenderRatio,pos[2]*nRenderRatio,pos[3]*nRenderRatio), fill*nRenderRatio, border_radius=border_radius*nRenderRatio )
s = pygame.transform.rotate( s, rotation_angle )
if nRenderRatio != 1: s = pygame.transform.smoothscale(s,(s.get_width()//nRenderRatio,s.get_height()//nRenderRatio))
incfromrotw = (s.get_width()-sw)//2
incfromroth = (s.get_height()-sh)//2
surface.blit( s, (pos[0]-surfcenterx+rotation_offset_center[0]+rw2-incfromrotw,pos[1]-surfcentery+rotation_offset_center[1]+rh2-incfromroth) )
You cannot rotate a rectangle drawn by pygame.draw.rect. You have to create a transparent pygame.Surface and rotate the Surface:
rect_surf = pygame.Surface((widht, height), pygame.SRCLAPHA)
rect_surf.fill(color)
See How do I rotate an image around its center using PyGame?, to rotate the Surface.
This code simulates rotating rectangles falling towards the ground. I used it in one of my games to make the background look awesome
import pygame
import random
class Square(pygame.sprite.Sprite):
def __init__(self, x, y):
super(Square, self).__init__()
self.win = win
self.color = (128, 128, 128)
self.speed = 3
self.angle = 0
self.side = random.randint(15, 40)
self.surface = pygame.Surface((self.side, self.side), pygame.SRCALPHA)
self.surface.set_colorkey((200,200,200))
self.rect = self.surface.get_rect(center=(x, y))
def update(self, win):
center = self.rect.center
self.angle = (self.angle + self.speed) % 360
image = pygame.transform.rotate(self.surface , self.angle)
self.rect = image.get_rect()
self.rect.center = center
self.rect.y += 1.5
if self.rect.top >= HEIGHT:
self.kill()
pygame.draw.rect(self.surface, self.color, (0,0, self.side, self.side), 4)
win.blit(image, self.rect)
if __name__ == '__main__':
pygame.init()
SCREEN = WIDTH, HEIGHT = 288, 512
win = pygame.display.set_mode(SCREEN, pygame.NOFRAME)
clock = pygame.time.Clock()
FPS = 60
count = 0
square_group = pygame.sprite.Group()
running = True
while running:
win.fill((200,200,200))
for event in pygame.event.get():
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_ESCAPE:
running = False
count += 1
if count % 100 == 0:
x = random.randint(40, WIDTH-40)
y = 0
square = Square(x, y)
square_group.add(square)
count = 0
square_group.update(win)
pygame.draw.rect(win, (30,30,30), (0, 0, WIDTH, HEIGHT), 8)
clock.tick(FPS)
pygame.display.update()
pygame.quit()
Here’s the output, it’s not an gif though
Now if you want color filled rectangle instead of bordered only, update this line on line 31
pygame.draw.rect(self.surface, self.color, (0,0, self.side, self.side))
and if you don’t want the rectangle to fall down comment line 26
I made a class which handles the rotation for you…
Extended from Ashish’s design
from pygame import Surface, transform
from consts import screen
class BaseEntity:
def __init__(self, x: int, y: int):
self.x = x
self.y = y
class Rectangle(BaseEntity):
def __init__(self, x: int, y: int, width: int, height: int, color: tuple):
super().__init__(x, y)
self.width = width
self.height = height
self.color = color
self.rotatation = 0
# the rectangle is a surface itself
self.surface = Surface((width, height))
self.surface.set_colorkey((0, 0, 0))
self.surface.fill(color)
self.rect = self.surface.get_rect()
def display(self, angle=None):
# updating values
self.surface.fill(
self.color
) # refill the surface color if you change it somewhere in the program
self.rect = self.surface.get_rect()
self.rect.center = (self.x, self.y)
# renderer
if angle is not None:
self.rotatation = angle
old_center = self.rect.center
new = transform.rotate(self.surface, self.rotatation)
self.rect = new.get_rect()
self.rect.center = old_center
screen.blit(new, self.rect)
Using a bit of trigonometry and the polygon function, I’m able to draw a rotated rectangle.
import math
import pygame.draw
def draw_rectangle(x, y, width, height, color, rotation=0):
"""Draw a rectangle, centered at x, y.
Arguments:
x (int/float):
The x coordinate of the center of the shape.
y (int/float):
The y coordinate of the center of the shape.
width (int/float):
The width of the rectangle.
height (int/float):
The height of the rectangle.
color (str):
Name of the fill color, in HTML format.
"""
points = []
# The distance from the center of the rectangle to
# one of the corners is the same for each corner.
radius = math.sqrt((height / 2)**2 + (width / 2)**2)
# Get the angle to one of the corners with respect
# to the x-axis.
angle = math.atan2(height / 2, width / 2)
# Transform that angle to reach each corner of the rectangle.
angles = [angle, -angle + math.pi, angle + math.pi, -angle]
# Convert rotation from degrees to radians.
rot_radians = (math.pi / 180) * rotation
# Calculate the coordinates of each point.
for angle in angles:
y_offset = -1 * radius * math.sin(angle + rot_radians)
x_offset = radius * math.cos(angle + rot_radians)
points.append((x + x_offset, y + y_offset))
pygame.draw.polygon(screen, color, points)
A concise and fast function to draw a rotated rectangle. Uses NumPy
def rectRotated(self, surface, rect, color, rotation):
"""
Draws a rotated Rect.
surface: pygame.Surface
rect: pygame.Rect
color: pygame.Color
rotation: float (degrees)
return: np.ndarray (vertices)
"""
# calculate the rotation in radians
rot_radians = -rotation * pi / 180
# calculate the points around the center of the rectangle, taking width and height into account
angle = atan2(rect.height / 2, rect.width / 2)
angles = [angle, -angle + pi, angle + pi, -angle]
radius = sqrt((rect.height / 2)**2 + (rect.width / 2)**2)
# create a numpy array of the points
points = np.array([
[rect.x + radius * cos(angle + rot_radians), rect.y + radius * sin(angle + rot_radians)]
for angle in angles
])
# draw the polygon
pygame.draw.polygon(surface, color, points)
# return the vertices of the rectangle
return points
In pygame I use pygame.draw.rect(screen, color, rectangle) for all the rectangles in my program. I want to be able to rotate these rectangles to any angle. I have seen the following code to rotate IMAGES but my question is with RECTANGLES.
pygame.transform.rotate(image, angle)
But I am working with rectangles, I don’t have an image or “surface” that I can rotate. When I try to rotate a rectangle with
rect = pygame.draw.rect(screen, self.color, self.get_rectang())
rotatedRect = pygame.transform.rotate(rect, self.rotation)
screen.blit(rotatedRect)
This gives TypeError: must be pygame.Surface, not pygame.Rect on the line with .rotate()
My question is, how can I rotate a and display a RECTANGLE(x,y,w,h), not an image, in pygame.
The linked post that this is a “potential duplicate” of is not a duplicate. One answer explains about the consequences of rotating a rectangle and the other uses code for rotating an image.
See the second answer here: Rotating a point about another point (2D)
I think rectangles can only be horiz or vertical in their oreintation. You need to define the corners and rotate them and then draw and fill between them.
The other way is to make a class
class myRect(pygame.Surface):
def __init__(self, parent, xpos, ypos, width, height):
super(myRect, self).__init__(width, height)
self.xpos = xpos
self.ypos = ypos
self.parent = parent
def update(self, parent):
parent.blit(self, (self.xpos, self.ypos))
def rotate(self, angle):
#(your rotation code goes here)
and use that instead, as then you will be able to rotate it using the transform function.
import pygame as py
# define constants
WIDTH = 500
HEIGHT = 500
FPS = 30
# define colors
BLACK = (0 , 0 , 0)
GREEN = (0 , 255 , 0)
# initialize pygame and create screen
py.init()
screen = py.display.set_mode((WIDTH , HEIGHT))
# for setting FPS
clock = py.time.Clock()
rot = 0
rot_speed = 2
# define a surface (RECTANGLE)
image_orig = py.Surface((100 , 100))
# for making transparent background while rotating an image
image_orig.set_colorkey(BLACK)
# fill the rectangle / surface with green color
image_orig.fill(GREEN)
# creating a copy of orignal image for smooth rotation
image = image_orig.copy()
image.set_colorkey(BLACK)
# define rect for placing the rectangle at the desired position
rect = image.get_rect()
rect.center = (WIDTH // 2 , HEIGHT // 2)
# keep rotating the rectangle until running is set to False
running = True
while running:
# set FPS
clock.tick(FPS)
# clear the screen every time before drawing new objects
screen.fill(BLACK)
# check for the exit
for event in py.event.get():
if event.type == py.QUIT:
running = False
# making a copy of the old center of the rectangle
old_center = rect.center
# defining angle of the rotation
rot = (rot + rot_speed) % 360
# rotating the orignal image
new_image = py.transform.rotate(image_orig , rot)
rect = new_image.get_rect()
# set the rotated rectangle to the old center
rect.center = old_center
# drawing the rotated rectangle to the screen
screen.blit(new_image , rect)
# flipping the display after drawing everything
py.display.flip()
py.quit()
a quick replacement of the base pygame function adding rotation:
def rectRotated( surface, color, pos, fill, border_radius, angle ):
"""
- angle in degree
"""
max_area = max(pos[2],pos[3])
s = pg.Surface((max_area,max_area))
s = s.convert_alpha()
s.fill((0,0,0,0))
pg.draw.rect(s, color,(0,0,pos[2],pos[3]),fill, border_radius=border_radius)
s = pygame.transform.rotate(s,angle)
surface.blit( s, (pos[0],pos[1]) )
a more complex version of the quick replacement, in which you can define an arbitrary rotation center point for your rectangle – even outside of it (tested in python3):
def rectRotated( surface, color, pos, fill, border_radius, rotation_angle, rotation_offset_center = (0,0), nAntialiasingRatio = 1 ):
"""
- rotation_angle: in degree
- rotation_offset_center: moving the center of the rotation: (-100,0) will turn the rectangle around a point 100 above center of the rectangle,
if (0,0) the rotation is at the center of the rectangle
- nAntialiasingRatio: set 1 for no antialising, 2/4/8 for better aliasing
"""
nRenderRatio = nAntialiasingRatio
sw = pos[2]+abs(rotation_offset_center[0])*2
sh = pos[3]+abs(rotation_offset_center[1])*2
surfcenterx = sw//2
surfcentery = sh//2
s = pg.Surface( (sw*nRenderRatio,sh*nRenderRatio) )
s = s.convert_alpha()
s.fill((0,0,0,0))
rw2=pos[2]//2 # halfwidth of rectangle
rh2=pos[3]//2
pg.draw.rect( s, color, ((surfcenterx-rw2-rotation_offset_center[0])*nRenderRatio,(surfcentery-rh2-rotation_offset_center[1])*nRenderRatio,pos[2]*nRenderRatio,pos[3]*nRenderRatio), fill*nRenderRatio, border_radius=border_radius*nRenderRatio )
s = pygame.transform.rotate( s, rotation_angle )
if nRenderRatio != 1: s = pygame.transform.smoothscale(s,(s.get_width()//nRenderRatio,s.get_height()//nRenderRatio))
incfromrotw = (s.get_width()-sw)//2
incfromroth = (s.get_height()-sh)//2
surface.blit( s, (pos[0]-surfcenterx+rotation_offset_center[0]+rw2-incfromrotw,pos[1]-surfcentery+rotation_offset_center[1]+rh2-incfromroth) )
You cannot rotate a rectangle drawn by pygame.draw.rect. You have to create a transparent pygame.Surface and rotate the Surface:
rect_surf = pygame.Surface((widht, height), pygame.SRCLAPHA)
rect_surf.fill(color)
See How do I rotate an image around its center using PyGame?, to rotate the Surface.
This code simulates rotating rectangles falling towards the ground. I used it in one of my games to make the background look awesome
import pygame
import random
class Square(pygame.sprite.Sprite):
def __init__(self, x, y):
super(Square, self).__init__()
self.win = win
self.color = (128, 128, 128)
self.speed = 3
self.angle = 0
self.side = random.randint(15, 40)
self.surface = pygame.Surface((self.side, self.side), pygame.SRCALPHA)
self.surface.set_colorkey((200,200,200))
self.rect = self.surface.get_rect(center=(x, y))
def update(self, win):
center = self.rect.center
self.angle = (self.angle + self.speed) % 360
image = pygame.transform.rotate(self.surface , self.angle)
self.rect = image.get_rect()
self.rect.center = center
self.rect.y += 1.5
if self.rect.top >= HEIGHT:
self.kill()
pygame.draw.rect(self.surface, self.color, (0,0, self.side, self.side), 4)
win.blit(image, self.rect)
if __name__ == '__main__':
pygame.init()
SCREEN = WIDTH, HEIGHT = 288, 512
win = pygame.display.set_mode(SCREEN, pygame.NOFRAME)
clock = pygame.time.Clock()
FPS = 60
count = 0
square_group = pygame.sprite.Group()
running = True
while running:
win.fill((200,200,200))
for event in pygame.event.get():
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_ESCAPE:
running = False
count += 1
if count % 100 == 0:
x = random.randint(40, WIDTH-40)
y = 0
square = Square(x, y)
square_group.add(square)
count = 0
square_group.update(win)
pygame.draw.rect(win, (30,30,30), (0, 0, WIDTH, HEIGHT), 8)
clock.tick(FPS)
pygame.display.update()
pygame.quit()
Here’s the output, it’s not an gif though
Now if you want color filled rectangle instead of bordered only, update this line on line 31
pygame.draw.rect(self.surface, self.color, (0,0, self.side, self.side))
and if you don’t want the rectangle to fall down comment line 26
I made a class which handles the rotation for you…
Extended from Ashish’s design
from pygame import Surface, transform
from consts import screen
class BaseEntity:
def __init__(self, x: int, y: int):
self.x = x
self.y = y
class Rectangle(BaseEntity):
def __init__(self, x: int, y: int, width: int, height: int, color: tuple):
super().__init__(x, y)
self.width = width
self.height = height
self.color = color
self.rotatation = 0
# the rectangle is a surface itself
self.surface = Surface((width, height))
self.surface.set_colorkey((0, 0, 0))
self.surface.fill(color)
self.rect = self.surface.get_rect()
def display(self, angle=None):
# updating values
self.surface.fill(
self.color
) # refill the surface color if you change it somewhere in the program
self.rect = self.surface.get_rect()
self.rect.center = (self.x, self.y)
# renderer
if angle is not None:
self.rotatation = angle
old_center = self.rect.center
new = transform.rotate(self.surface, self.rotatation)
self.rect = new.get_rect()
self.rect.center = old_center
screen.blit(new, self.rect)
Using a bit of trigonometry and the polygon function, I’m able to draw a rotated rectangle.
import math
import pygame.draw
def draw_rectangle(x, y, width, height, color, rotation=0):
"""Draw a rectangle, centered at x, y.
Arguments:
x (int/float):
The x coordinate of the center of the shape.
y (int/float):
The y coordinate of the center of the shape.
width (int/float):
The width of the rectangle.
height (int/float):
The height of the rectangle.
color (str):
Name of the fill color, in HTML format.
"""
points = []
# The distance from the center of the rectangle to
# one of the corners is the same for each corner.
radius = math.sqrt((height / 2)**2 + (width / 2)**2)
# Get the angle to one of the corners with respect
# to the x-axis.
angle = math.atan2(height / 2, width / 2)
# Transform that angle to reach each corner of the rectangle.
angles = [angle, -angle + math.pi, angle + math.pi, -angle]
# Convert rotation from degrees to radians.
rot_radians = (math.pi / 180) * rotation
# Calculate the coordinates of each point.
for angle in angles:
y_offset = -1 * radius * math.sin(angle + rot_radians)
x_offset = radius * math.cos(angle + rot_radians)
points.append((x + x_offset, y + y_offset))
pygame.draw.polygon(screen, color, points)
A concise and fast function to draw a rotated rectangle. Uses NumPy
def rectRotated(self, surface, rect, color, rotation):
"""
Draws a rotated Rect.
surface: pygame.Surface
rect: pygame.Rect
color: pygame.Color
rotation: float (degrees)
return: np.ndarray (vertices)
"""
# calculate the rotation in radians
rot_radians = -rotation * pi / 180
# calculate the points around the center of the rectangle, taking width and height into account
angle = atan2(rect.height / 2, rect.width / 2)
angles = [angle, -angle + pi, angle + pi, -angle]
radius = sqrt((rect.height / 2)**2 + (rect.width / 2)**2)
# create a numpy array of the points
points = np.array([
[rect.x + radius * cos(angle + rot_radians), rect.y + radius * sin(angle + rot_radians)]
for angle in angles
])
# draw the polygon
pygame.draw.polygon(surface, color, points)
# return the vertices of the rectangle
return points