Develop Reference

How to I make multiple rects in different places? [duplicate]

Right now, my game blits all the images in random positions correctly and also gets the rect of the images correctly, but I can´t figure out how to use colliderect to make sure the images don´t overlap. How could it work for my code?
Also I´m trying to make the first text fade out and I don´t know why it doesn´t work for me.
Here is the code:
class GAME1:
def __init__(self, next_scene):
self.background = pygame.Surface(size)
# Create an array of images with their rect
self.images = []
self.rects = []
self.imagenes1_array = ['autobus.png','coche.png','barco.png','autobus2.png','grua.png','bici.png']
for i in self.imagenes1_array:
# We divide in variables so we can then get the rect of the whole Img (i2)
i2 = pygame.image.load(i)
self.images.append(i2)
s = pygame.Surface(i2.get_size())
r = s.get_rect()
# Trying to use colliderect so it doesnt overlap
if pygame.Rect.colliderect(r,r) == True:
x = random.randint(300,1000)
y = random.randint(200,700)
self.rects.append(r)
def start(self, gamestate):
self.gamestate = gamestate
for rect in self.rects:
# Give random coordinates (we limit the dimensions (x,y))
x = random.randint(300,1000)
y = random.randint(200,700)
rect.x = x
rect.y = y
def draw(self,screen):
self.background = pygame.Surface(size)
font = pygame.font.SysFont("comicsansms",70)
# First half (Show image to remember)
text1 = font.render('¡A recordar!',True, PURPLE)
text1_1 = text1.copy()
# This surface is used to adjust the alpha of the txt_surf.
alpha_surf = pygame.Surface(text1_1.get_size(), pygame.SRCALPHA)
alpha = 255 # The current alpha value of the surface.
if alpha > 0:
alpha = max(alpha-4, 0)
text1_1 = text1.copy()
alpha_surf.fill((255, 255, 255, alpha))
text1_1.blit(alpha_surf, (0,0), special_flags = pygame.BLEND_RGBA_MULT)
screen.blit(text1_1, (600,50))
# Second half (Show all similar images)
text2 = font.render('¿Cuál era el dibujo?',True, PURPLE)
#screen.blit(text2, (500,50))
for i in range(len(self.images)):
#colliding = pygame.Rect.collidelistall(self.rects)
screen.blit(self.images[i], (self.rects[i].x, self.rects[i].y))
def update(self, events, dt):
for event in events:
if event.type == pygame.MOUSEBUTTONDOWN:
for rect in self.rects:
if rect.collidepoint(event.pos):
print('works!')

Use collidelist() to test test if one rectangle in a list intersects:
for i in self.imagenes1_array:
s = pygame.image.load(i)
self.images.append(s)
r = s.get_rect()
position_set = False
while not position_set:
r.x = random.randint(300,1000)
r.y = random.randint(200,700)
margin = 10
rl = [rect.inflate(margin*2, margin*2) for rect in self.rects]
if len(self.rects) == 0 or r.collidelist(rl) < 0:
self.rects.append(r)
position_set = True
See the minimal example, that uses the algorithm to generate random not overlapping rectangles:
import pygame
import random
pygame.init()
window = pygame.display.set_mode((400, 400))
clock = pygame.time.Clock()
def new_recs(rects):
rects.clear()
for _ in range(10):
r = pygame.Rect(0, 0, random.randint(30, 40), random.randint(30, 50))
position_set = False
while not position_set:
r.x = random.randint(10, 340)
r.y = random.randint(10, 340)
margin = 10
rl = [rect.inflate(margin*2, margin*2) for rect in rects]
if len(rects) == 0 or r.collidelist(rl) < 0:
rects.append(r)
position_set = True
rects = []
new_recs(rects)
run = True
while run:
clock.tick(60)
for event in pygame.event.get():
if event.type == pygame.QUIT:
run = False
elif event.type == pygame.KEYDOWN:
new_recs(rects)
window.fill(0)
for r in rects:
pygame.draw.rect(window, (255, 0, 0), r)
pygame.display.flip()
pygame.quit()
exit()

How to give a warning when a moving object deviates from a path by a specific margin?

In my pygame-code, I have a drone that is supposed to follow a flight path.
I used pygame.draw.lines to draw lines between specified points. Now, I have a flight path with 10 points where after each point the path angle changes (a bit like a zigzag). The player can move the drone by pressing the keys.
My goal is to print a warning once the drone deviates from the path, e.g. by +/-30. I have been racking my brain for two days but can't come up with a condition to detect a deviation. I just can't figure out how to approach this.
I can determine the drone's x-coordinate at any time but how do I determine the offset from the path? I have attached an image to visualize my problem.
Edit:
As I am a beginner my code is a mess but when copy-pasting it, I guess only the lines 35-91 are interesting. Thank you for any kind of advice in advance!!
import pygame
import pygame.gfxdraw
import random
import sys
import math
pygame.init()
# Define some colors
black = (0,0,0)
white = (255,255,255)
red = (255,0,0)
red_transp = (255,0,0, 150)
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
BLUE = (0, 0, 255)
GREEN = (0, 255, 0)
RED = (255, 0, 0)
X = 0
Y = 250
#Display
display_width, display_height = 1200, 700
h_width, h_height = display_width/2, display_height/2
gameDisplay = pygame.display.set_mode((display_width,display_height))
pygame.display.set_caption('Game Display')
#Drone Sprite Image Load Function
droneImg_interim = pygame.image.load('drone.png')
droneImg = pygame.transform.scale(droneImg_interim, [50,50])
drone_width, drone_height = droneImg.get_rect().size
#Create 11 Waypoints with the same coordinates
p1=[X, Y]
p2=[X, Y]
p3=[X, Y]
p4=[X, Y]
p5=[X, Y]
p6=[X, Y]
p7=[X, Y]
p8=[X, Y]
p9=[X, Y]
p10=[X, Y]
p11=[X, Y]
pointlist = [p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11]
x_min=drone_width
x_max=100
#Setting new x-coordinate for each point
for i in pointlist:
i[0] = random.randrange(x_min, x_max)
x_min+=250
x_max+=250
#Setting new y-coordinate for each point
for i in range(len(pointlist)):
if i == 0:
pointlist[i][1] = random.randrange(200, 400)
else:
prev = pointlist[i-1][1]
pointlist[i][1] = random.randrange(200, prev+100)
#Plotting pointlist on gameDisplay and connecting dots
def flightpath(pointlist):
pygame.draw.lines(gameDisplay, (255, 0, 0), False, pointlist, 2)
def margin(x):
for i in range(len(pointlist)-1):
p1_x = pointlist[i][0]
p2_x = pointlist[i+1][0]
p1_y = pointlist[i][1]
p2_y = pointlist[i+1][1]
distance_x = p2_x - p1_x
distance = math.sqrt((p2_x-p1_x)**2+(p2_y-p1_y)**2)
halfwaypoint_x = math.sqrt((p2_x - p1_x)**2)/2 + p1_x
halfwaypoint_y = math.sqrt((p2_y - p1_y)**2)/2 + p1_y
if p2_y < p1_y:
angle_rad = math.acos(distance_x/distance)
elif p2_y > p1_y:
angle_rad = 0 - math.acos(distance_x/distance)
angle_deg = math.degrees(angle_rad)
rect_width = distance
rect_height = 60
"""
This part of the code is meant for displaying the margins (the rectangles) around the flight path on the display.
marginSize = (rect_width, rect_height)
surface = pygame.Surface(marginSize, pygame.SRCALPHA)
surface.fill((255,0,0,25))
rotated_surface = pygame.transform.rotate(surface, angle_deg)
#new_rect = rotated_surface.get_rect(center = surface.get_rect(center = ((pointlist[i][0], pointlist[i][1]))).center)
new_rect = rotated_surface.get_rect(center = surface.get_rect(center = ((halfwaypoint_x, halfwaypoint_y))).center)
#gameDisplay.blit(rotated_surface, new_rect)
"""
#Placing drone on the screen
def drone(x,y):
rect = droneImg.get_rect ()
rect.center=(x, y)
gameDisplay.blit(droneImg,rect)
def displayMSG(value,ttext,posx,posy):
myFont = pygame.font.SysFont("Verdana", 12)
Label = myFont.render(ttext, 1, black)
Value = myFont.render(str(value), 1, black)
gameDisplay.blit(Label, (posx, posy))
gameDisplay.blit(Value, (posx + 100, posy))
#Main Loop Object
def game_loop():
global X, Y, FThrustX, FThrustY, FDragY, Time
FThrustY = 0
gameExit = False
while not gameExit:
#Event Checker (Keyboard, Mouse, etc.)
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
sys.exit()
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_ESCAPE:
pygame.quit()
sys.exit()
keys = pygame.key.get_pressed() #checking pressed keys
if keys[pygame.K_LEFT]:
X -= 1
if keys[pygame.K_RIGHT]:
X +=1
if keys[pygame.K_DOWN]:
Y += 1
if keys[pygame.K_UP]:
Y -=1
#Display Background Fill
gameDisplay.fill(white)
#Plot flightpath
flightpath(pointlist)
#YS: Determine the position of the mouse
current_pos_x, current_pos_y = pygame.mouse.get_pos()
displayMSG(current_pos_x,'x:',20,665)
displayMSG(current_pos_y,'y:',20,680)
#Plot margin
margin(5)
#Move Drone Object
drone(X,Y)
#Determine the position of the mouse
current_pos_x, current_pos_y = pygame.mouse.get_pos()
#No exceeding of display edge
if X > display_width - drone_width: X = display_width - drone_width
if Y > display_height - drone_height: Y = display_height - drone_height
if X < drone_width: X = drone_width
if Y < drone_height: Y = drone_height
pygame.display.update()
#MAIN
game_loop()
pygame.quit()
sys.exit()

One approach is to find the minimum distance between the center of the drone and the line.
Write the function that calculates the minimum distance from a point to a line segment. To do this, use pygame.math.Vector2 and the Dot product:
def distance_point_linesegment(pt, l1, l2):
LV = pygame.math.Vector2(l2[0] - l1[0], l2[1] - l1[1])
PV = pygame.math.Vector2(pt[0] - l1[0], pt[1]- l1[1])
dotLP = LV.dot(PV)
if dotLP < 0:
return PV.length()
if dotLP > LV.length_squared():
return pygame.math.Vector2(pt[0] - l2[0], pt[1]- l2[1]).length()
NV = pygame.math.Vector2(l1[1] - l2[1], l2[0] - l1[0])
return abs(NV.normalize().dot(PV))
Find the line segment with the shortest distance in a loop:
def minimum_distance(pt, pointlist):
min_dist = -1
for i in range(len(pointlist)-1):
dist = distance_point_linesegment(pt, pointlist[i], pointlist[i+1])
if i == 0 or dist < min_dist:
min_dist = dist
return min_dist
Create an alert when the distance exceeds a certain threshold:
def game_loop():
# [...]
while not gameExit:
# [...]
dist_to_path = minimum_distance((X, Y), pointlist)
if dist_to_path > 25:
pygame.draw.circle(gameDisplay, (255, 0, 0), (X, Y), 25, 4)
drone(X,Y
# [...]
Another possible solution is to use pygame.Rect.clipline and detect the collision of the line segments and the rectangle surrounding the drone:
def intersect_rect(rect, pointlist):
for i in range(len(pointlist)-1):
if rect.clipline(pointlist[i], pointlist[i+1]):
return True
return False
def game_loop():
# [...]
while not gameExit:
# [...]
if not intersect_rect(droneImg.get_rect(center = (X, Y)), pointlist):
pygame.draw.circle(gameDisplay, (255, 0, 0), (X, Y), 25, 4)
drone(X,Y
# [...]

The interesting part of the question is of course finding the nearest point on the desired path to the actual position; distance is easy. The hard part of that is in turn identifying the nearest element (line segment) of the path; projecting onto it is also straightforward.
If the path is simple enough (in particular, if it doesn’t branch and it’s impossible/disallowed to skip sections at a self-intersection), you can finesse that part by just maintaining that current element in a variable and updating it to the previous or next element when the projection onto one of them is closer than the projection onto the current one. This is a typical algorithm used by racing games to determine the instantaneous order of racers.

Problem with animating a sprite in pygame

i have a problem with this code, i am a new person with programming and been using the book "how to think like a computer scientist 3rd edition" and he did not solve exercise 2 of chapter 17 this given: "he deliberately left a mistake in the code to animate Duke. If you click on one of the checkerboard squares to the right of Duke, he salutes anyway. Why? Find a one-line solution to the error ", I've tried many forms but I have not succeeded, I leave you all the code and the images that I have used
PS: images must have the name: ball.png and duke_spritesheet.png
import pygame
gravity = 0.025
my_clock = pygame.time.Clock()
class QueenSprite:
def __init__(self, img, target_posn):
self.image = img
self.target_posn = target_posn
(x, y) = target_posn
self.posn = (x, 0) # Start ball at top of its column
self.y_velocity = 0 # with zero initial velocity
def update(self):
self.y_velocity += gravity
(x, y) = self.posn
new_y_pos = y + self.y_velocity
(target_x, target_y) = self.target_posn # Unpack the position
dist_to_go = target_y - new_y_pos # How far to our floor?
if dist_to_go < 0: # Are we under floor?
self.y_velocity = -0.65 * self.y_velocity # Bounce
new_y_pos = target_y + dist_to_go # Move back above floor
self.posn = (x, new_y_pos) # Set our new position.
def draw(self, target_surface): # Same as before.
target_surface.blit(self.image, self.posn)
def contains_point(self, pt):
""" Return True if my sprite rectangle contains point pt """
(my_x, my_y) = self.posn
my_width = self.image.get_width()
my_height = self.image.get_height()
(x, y) = pt
return ( x >= my_x and x < my_x + my_width and
y >= my_y and y < my_y + my_height)
def handle_click(self):
self.y_velocity += -2 # Kick it up
class DukeSprite:
def __init__(self, img, target_posn):
self.image = img
self.posn = target_posn
self.anim_frame_count = 0
self.curr_patch_num = 0
def update(self):
if self.anim_frame_count > 0:
self.anim_frame_count = (self.anim_frame_count + 1 ) % 60
self.curr_patch_num = self.anim_frame_count // 6
def draw(self, target_surface):
patch_rect = (self.curr_patch_num * 50, 0,
50, self.image.get_width())
target_surface.blit(self.image, self.posn, patch_rect)
def contains_point(self, pt):
""" Return True if my sprite rectangle contains pt """
(my_x, my_y) = self.posn
my_width = self.image.get_width()
my_height = self.image.get_height()
(x, y) = pt
return ( x >= my_x and x < my_x + my_width and
y >= my_y and y < my_y + my_height)
def handle_click(self):
if self.anim_frame_count == 0:
self.anim_frame_count = 5
def draw_board(the_board):
""" Draw a chess board with queens, as determined by the the_board. """
pygame.init()
colors = [(255,0,0), (0,0,0)] # Set up colors [red, black]
n = len(the_board) # This is an NxN chess board.
surface_sz = 480 # Proposed physical surface size.
sq_sz = surface_sz // n # sq_sz is length of a square.
surface_sz = n * sq_sz # Adjust to exactly fit n squares.
# Create the surface of (width, height), and its window.
surface = pygame.display.set_mode((surface_sz, surface_sz))
ball = pygame.image.load("ball.png")
# Use an extra offset to centre the ball in its square.
# If the square is too small, offset becomes negative,
# but it will still be centered :-)
ball_offset = (sq_sz-ball.get_width()) // 2
all_sprites = [] # Keep a list of all sprites in the game
# Create a sprite object for each queen, and populate our list.
for (col, row) in enumerate(the_board):
a_queen = QueenSprite(ball,
(col*sq_sz+ball_offset, row*sq_sz+ball_offset))
all_sprites.append(a_queen)
# Load the sprite sheet
duke_sprite_sheet = pygame.image.load("duke_spritesheet.png")
# Instantiate two duke instances, put them on the chessboard
duke1 = DukeSprite(duke_sprite_sheet,(sq_sz*2, 0))
duke2 = DukeSprite(duke_sprite_sheet,(sq_sz*5, sq_sz))
# Add them to the list of sprites which our game loop manages
all_sprites.append(duke1)
all_sprites.append(duke2)
while True:
# Look for an event from keyboard, mouse, etc.
ev = pygame.event.poll()
if ev.type == pygame.QUIT:
break;
if ev.type == pygame.KEYDOWN:
key = ev.dict["key"]
if key == 27: # On Escape key ...
break # leave the game loop.
if key == ord("r"):
colors[0] = (255, 0, 0) # Change to red + black.
elif key == ord("g"):
colors[0] = (0, 255, 0) # Change to green + black.
elif key == ord("b"):
colors[0] = (0, 0, 255) # Change to blue + black.
if ev.type == pygame.MOUSEBUTTONDOWN: # Mouse gone down?
posn_of_click = ev.dict["pos"] # Get the coordinates.
for sprite in all_sprites:
if sprite.contains_point(posn_of_click):
sprite.handle_click()
break
for sprite in all_sprites:
sprite.update()
# Draw a fresh background (a blank chess board)
for row in range(n): # Draw each row of the board.
c_indx = row % 2 # Alternate starting color
for col in range(n): # Run through cols drawing squares
the_square = (col*sq_sz, row*sq_sz, sq_sz, sq_sz)
surface.fill(colors[c_indx], the_square)
# Now flip the color index for the next square
c_indx = (c_indx + 1) % 2
# Ask every sprite to draw itself.
for sprite in all_sprites:
sprite.draw(surface)
my_clock.tick(60) # Waste time so that frame rate becomes 60 fps
pygame.display.flip()
pygame.quit()
if __name__ == "__main__":
draw_board([0, 5, 3, 1, 6, 4, 2]) # 7 x 7 to test window size
PS: I think the error is here but it did not succeed
return ( x >= my_x and x + my_width and y >= my_y and y < my_y + my_height)

The issue is caused by the face, that "duke_spritesheet.png" is a sprite sheet. When you define the rectangular region which is covered by the object, then you have to use the width of a single image, rather than the width of the entire sprite sheet:
my_width = self.image.get_width()
my_width = 50
Change this in the method contains_point of the class DukeSprite:
class DukeSprite:
# [...]
def contains_point(self, pt):
""" Return True if my sprite rectangle contains pt """
(my_x, my_y) = self.posn
my_width = 50
my_height = self.image.get_height()
(x, y) = pt
return ( x >= my_x and x < my_x + my_width and
y >= my_y and y < my_y + my_height)

Make cursor unable to move through sprite pygame

So my question is simple: How do I make a sprite that my mouse can't pass through? I've been experimenting, and I found an unreliable way to do it that is also super glitchy. If anyone knows how I might go about this, please help.
Here is the code that I am currently using:
import pygame
import pyautogui
import sys
import time
pygame.init()
game_display = pygame.display.set_mode((800,600))
pygame.mouse.set_visible(True)
pygame.event.set_grab(True)
exit = False
class Wall(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.Surface((30, 100))
self.image.fill((255, 255, 255))
self.rect = self.image.get_rect()
self.rect.center = (200, 200)
def collision(self):
loc = pygame.mouse.get_pos()
yy = loc[1]
xx = loc[0]
if yy >= self.rect.top and yy <= self.rect.bottom and xx >= self.rect.left and xx <= self.rect.right:
if xx >= 200:
pyautogui.move(216 - xx, 0)
if xx <= 200:
pyautogui.move(-xx + 184, 0)
w = Wall()
all_sprites = pygame.sprite.Group()
all_sprites.add(w)
print(w.rect.top)
print(w.rect.bottom)
while (not exit):
mouse_move = (0,0)
for event in pygame.event.get():
if event.type == pygame.QUIT:
exit = True
elif event.type == pygame.KEYDOWN:
if event.key == pygame.K_ESCAPE:
exit = True
w.collision()
clock = pygame.time.Clock()
game_display.fill((0, 0, 0))
clock.tick(30)
all_sprites.update()
all_sprites.draw(game_display)
pygame.display.flip()
pygame.quit()
note: please ignore my extra import statements, I am going to use them for later.

To do what you want you have to check if the line form the previous mouse position to the new mouse position intersects the rectangle. Write a function IntersectLineRec which checks for the intersection and use it and returns a list of intersection points, sorted by the distance.
The function returns a list of tules whith points and distances:
e.g.
[((215.0, 177.0), 12.0), ((185.0, 177.0), 42.0)]
prev_loc = pygame.mouse.get_pos()
class Wall(pygame.sprite.Sprite):
# [...]
def collision(self):
global prev_loc
loc = pygame.mouse.get_pos()
intersect = IntersectLineRec(prev_loc, loc, self.rect)
prev_loc = loc
if intersect:
ip = [*intersect[0][0]]
for i in range(2):
tp = self.rect.center[i] if ip[i] == loc[i] else loc[i]
ip[i] += -3 if ip[i] < tp else 3
pyautogui.move(ip[0]-loc[0], ip[1]-loc[1])
prev_loc = loc = ip
The function IntersectLineRec has to check if one of the 4 outer lines between the 4 corners of the rectangle inter sects the line between the mouse positions:
def IntersectLineRec(p1, p2, rect):
iL = [
IntersectLineLine(p1, p2, rect.bottomleft, rect.bottomright),
IntersectLineLine(p1, p2, rect.bottomright, rect.topright),
IntersectLineLine(p1, p2, rect.topright, rect.topleft),
IntersectLineLine(p1, p2, rect.topleft, rect.bottomleft) ]
iDist = [(i[1], pygame.math.Vector2(i[1][0] - p1[0], i[1][1] - p1[1]).length()) for i in iL if i[0]]
iDist.sort(key=lambda t: t[1])
return iDist
IntersectLineRec checks if to endless lines, which are defined by to points are intersecting. Then it checks if the intersection point is in the rectangles which are defined by the each of the lines (the line is the diagonal of the rectangle):
def IntersectLineLine(l1_p1, l1_p2, l2_p1, l2_p2):
isect, xPt = IntersectEndlessLineLine(l1_p1, l1_p2, l2_p1, l2_p2)
isect = isect and PtInRect(xPt, l1_p1, l1_p2) and PtInRect(xPt, l2_p1, l2_p2)
return isect, xPt
To check if a point is in an axis aligned rectangle has to check if both coordinates of the point are in the range of the coordinates of the rectangle:
def InRange(coord, range_s, range_e):
if range_s < range_e:
return coord >= range_s and coord <= range_e
return coord >= range_e and coord <= range_s
def PtInRect(pt, lp1, lp2):
return InRange(pt[0], lp1[0], lp2[0]) and InRange(pt[1], lp1[1], lp2[1])
The intersection of to endless lines can be calculated like this:
def IntersectEndlessLineLine(l1_p1, l1_p2, l2_p1, l2_p2):
# calculate the line vectors and test if both lengths are > 0
P = pygame.math.Vector2(*l1_p1)
Q = pygame.math.Vector2(*l2_p1)
line1 = pygame.math.Vector2(*l1_p2) - P
line2 = pygame.math.Vector2(*l2_p2) - Q
if line1.length() == 0 or line2.length() == 0:
return (False, (0, 0))
# check if the lines are not parallel
R, S = (line1.normalize(), line2.normalize())
dot_R_nvS = R.dot(pygame.math.Vector2(S[1], -S[0]))
if abs(dot_R_nvS) < 0.001:
return (False, (0, 0))
# calculate the intersection point of the lines
# t = dot(Q-P, (S.y, -S.x)) / dot(R, (S.y, -S.x))
# X = P + R * t
ptVec = Q-P
t = ptVec.dot(pygame.math.Vector2(S[1], -S[0])) / dot_R_nvS
xPt = P + R * t
return (True, (xPt[0], xPt[1]))
See the animation:

Mandelbrot set displays incorrectly

This is my attempt to program the Mandelbrot set in Python 3.5 using the Pygame module.
import math, pygame
pygame.init()
def mapMandelbrot(c,r,dim,xRange,yRange):
x = (dim-c)/dim
y = (dim-r)/dim
#print([x,y])
x = x*(xRange[1]-xRange[0])
y = y*(yRange[1]-yRange[0])
x = xRange[0] + x
y = yRange[0] + y
return [x,y]
def checkDrawBox(surface):
for i in pygame.event.get():
if i.type == pygame.QUIT:
pygame.quit()
elif i.type == pygame.MOUSEBUTTONDOWN:
startXY = pygame.mouse.get_pos()
boxExit = False
while boxExit == False:
for event in pygame.event.get():
if event.type == pygame.MOUSEBUTTONUP:
boxExit = True
if boxExit == True:
return [startXY,pygame.mouse.get_pos()]
pygame.draw.rect(surface,[255,0,0],[startXY,[pygame.mouse.get_pos()[0]-startXY[0],pygame.mouse.get_pos()[1]-startXY[1]]],1)
pygame.display.update()
def setup():
dimensions = 500
white = [255,255,255]
black = [0,0,0]
checkIterations = 100
canvas = pygame.display.set_mode([dimensions,dimensions])
canvas.fill(black)
xRange = [-2,2]
yRange = [-2,2]
xRangePrev = [0,0]
yRangePrev = [0,0]
newxRange = [0,0]
newyRange = [0,0]
while True:
if not ([xRange,yRange] == [xRangePrev,yRangePrev]):
draw(dimensions, canvas, xRange, yRange, checkIterations)
pygame.display.update()
xRangePrev = xRange
yRangePrev = yRange
box = checkDrawBox(canvas)
if box != None:
maxX = max([box[0][0],box[1][0]])
maxY = max([box[0][1],box[1][1]])
newxRange[0] = mapMandelbrot(box[0][0],0,dimensions,xRange,yRange)[0]
newxRange[1] = mapMandelbrot(box[1][0],0,dimensions,xRange,yRange)[0]
newyRange[0] = mapMandelbrot(0,box[0][1],dimensions,xRange,yRange)[1]
newyRange[1] = mapMandelbrot(0,box[1][1],dimensions,xRange,yRange)[1]
xRange = newxRange
yRange = newyRange
def draw(dim, surface, xRange, yRange, checkIterations):
for column in range(dim):
for row in range(dim):
greyVal = iteration(0,0,mapMandelbrot(column,row,dim,xRange,yRange),checkIterations,checkIterations)
surface.set_at([dim-column,row],greyVal)
def iteration(a, b, c, iterCount, maxIter):
a = (a*a) - (b*b) + c[0]
b = (2*a*b) + c[1]
iterCount = iterCount - 1
if iterCount == 0:
return [0,0,0]
elif abs(a+b) > 17:
b = (iterCount/maxIter)*255
return [b,b,b]
else:
return iteration(a,b,c,iterCount,maxIter)
setup()
I believe that the iteration algorithm is correct, but the output doesn't look right:
Wondering what might be the problem? Sorry for the code dump, just not sure which part may cause it to look like that.

Fascinating bug -- it literally looks like a squashed bug :)
The problem lies in the two lines:
a = (a*a) - (b*b) + c[0]
b = (2*a*b) + c[1]
You are changing the meaning of a in the first line, hence using the wrong a in the second.
The fix is as simple as:
a, b = (a*a) - (b*b) + c[0], (2*a*b) + c[1]
which will cause the same value of a to be used in calculating the right hand side.
It would be interesting to work out just what your bug has produced. Even though it isn't the Mandelbrot set, it seems to be an interesting fractal in its own right. In that sense, you had a very lucky bug. 99% percent of the times, bugs lead to garbage, but every now and then they produce something quite interesting, but simply unintended.
On Edit:
The Mandelbrot set is based on iterating the complex polynomial:
f(z) = z^2 + c
The pseudo-Mandelbrot set which this bug has produced is based on iterating the function
f(z) = Re(z^2 + c) + i*[2*Re(z^2 + c)*Im(z) + Im(c)]
where Re() and Im() are the operators which extract the real and imaginary parts of a complex number. This isn't a polynomial in z, though it is easy to see that it is a polynomial in z,z* (where z* is the complex conjugate of z). Since it is a fairly natural bug, it is almost certain that this has appeared somewhere in the literature on the Mandelbrot set, though I don't remember ever seeing it.

I decided to learn about the mandelbrot set and wrote my own version! I used python's complex data type, which should make the mandelbrot calculation for each pixel a bit clearer. Here is a screenshot of the result:
And here is the source code/code dump:
import pygame
import sys
def calc_complex_coord(x, y):
real = min_corner.real + x * (max_corner.real - min_corner.real) / (width - 1.0)
imag = min_corner.imag + y * (max_corner.imag - min_corner.imag) / (height - 1.0)
return complex(real, imag)
def calc_mandelbrot(c):
z = c
for i in range(1, max_iterations+1):
if abs(z) > 2:
return i
z = z*z + c
return i
def calc_color_score(i):
if i == max_iterations:
return black
frac = 255.0 - (255.0 * i / max_iterations)
return (frac, frac, frac)
def update_mandelbrot():
for y in range(height):
for x in range(width):
c = calc_complex_coord(x, y)
mandel_score = calc_mandelbrot(c)
color = calc_color_score(mandel_score)
mandel_surface.set_at((x, y), color)
if __name__ == "__main__":
pygame.init()
(width, height) = (500, 500)
display = pygame.display.set_mode((width, height))
pygame.display.set_caption("Mandelbrot Magic")
clock = pygame.time.Clock()
mandel_surface = pygame.Surface((width, height))
black = (0, 0, 0)
red = (255, 0, 0)
max_iterations = 50
min_corner = complex(-2, -2)
max_corner = complex(2, 2)
box = pygame.Rect(0, 0, width, height)
update_mandel = True
draw_box = False
while True:
for event in pygame.event.get():
if event.type == pygame.QUIT:
sys.exit()
elif event.type == pygame.MOUSEBUTTONDOWN:
x, y = event.pos
box = pygame.Rect(x, y, 0, 0)
draw_box = True
elif event.type == pygame.MOUSEMOTION:
x, y = event.pos
if draw_box:
box = pygame.Rect(box.left, box.top, x - box.left, y - box.top)
elif event.type == pygame.MOUSEBUTTONUP:
x, y = event.pos
update_mandel = True
display.blit(mandel_surface, (0, 0))
if draw_box:
pygame.draw.rect(display, red, box, 1)
if update_mandel:
box.normalize()
new_min_corner = calc_complex_coord(box.left, box.top)
new_max_corner = calc_complex_coord(box.right, box.bottom)
min_corner, max_corner = new_min_corner, new_max_corner
update_mandelbrot()
update_mandel = False
draw_box = False
pygame.display.update()
clock.tick(60)
The two issues with this code are that one, it is quite slow in updating the mandelbrot set, and two, the aspect ratios get distorted if you work with non-square windows or box-selections. Let me know if any of the code is unclear!