Develop Reference

Rotating the player about the center point in pygame

I am making a game where there are two players and they can shoot each other. Their movement will be defined by a rotation around a fixed point, the point will be(600, 300), which is the center of our screen. The player will keep rotating around the point as long as they are pressing a certain button(which is keep providing force to our player) else they will fall(due to gravity). I think it would help to think of it as a ball attached to a point using a string. The string is attached as long as a button is pressed and gets unattached as soon as the button is released and the ball flies off. Here is my player class
class Player:
def __init__(self):
self.pos = [500, 200]
self.width = 30
self.height = 30
self.player = pygame.image.load("player.png").convert_alpha()
self.player = pygame.transform.scale(self.player, (self.width, self.height))
self.rect = self.player.get_rect()
self.rotated_player = None
self.anguler_vel = 0
self.Fg = 0.05
self.Fp = 0
self.arm_length = 0
Fp is the force perpendicular to the force of gravityFg. Fg is the force which is pulling it down on our player. Fp is defined by math.sin(theta) * Fg. I am keeping track of Fp because i want the player to keep moving in the direction of rotation after its unattatched from the string. arm_length is the length of the string.
I have a Point class, which is the point about which our player will rotate. Here's the point class.
class Point:
def __init__(self,x, y):
self.pos = [x, y]
dx = self.pos[0] - player.pos[0]
dy = self.pos[1] - player.pos[1]
self.angle = math.atan2(dy, dx)
Now, i need help with the actual rotation itself. I am aware that adding a certain value to the angle every single frame would make it go around. But how would i make it go around a certain point that i specify and how would the arm length tie into this?. I find that it is really difficult to implement all of this because the y-axis is flipped and all the positional values have to be scaled down when using them in calculations because of the FPS rate. Any help on how this is done would be appreciated as well. Thanks

When you use pygame.transform.rotate the size of the new rotated image is increased compared to the size of the original image. You must make sure that the rotated image is placed so that its center remains in the center of the non-rotated image. To do this, get the rectangle of the original image and set the position. Get the rectangle of the rotated image and set the center position through the center of the original rectangle. e.g.:
def rotate_center(image, rect, angle):
rotated_image = pygame.transform.rotate(image, angle)
new_rect = rotated_image.get_rect(center = rect.center)
return rotated_image, new_rect
screen.blit(*rotate_center(image, image_rect, angle))
Alos see How do I rotate an image around its center using PyGame? and How to rotate an image(player) to the mouse direction?

Pygame: How do I blit and rotate an image to connect two points on the screen?

Here is a test program. I started with two random dots and the line connecting them. Now, I want to take a given image (with x,y dimensions of 79 x 1080) and blit it on top of the guide line. I understand that arctan will give me the angle between the points on a cartesian grid, but because y is backwards the screen (x,y), I have to invert some values. I'm confused about the negating step.
If you run this repeatedly, you'll see the image is always parallel to the line, and sometimes on top, but not consistently.
import math
import pygame
import random
pygame.init()
screen = pygame.display.set_mode((600,600))
#target = (126, 270)
#start = (234, 54)
target = (random.randrange(600), random.randrange(600))
start = (random.randrange(600), random.randrange(600))
BLACK = (0,0,0)
BLUE = (0,0,128)
GREEN = (0,128,0)
pygame.draw.circle(screen, GREEN, start, 15)
pygame.draw.circle(screen, BLUE, target, 15)
pygame.draw.line(screen, BLUE, start, target, 5)
route = pygame.Surface((79,1080))
route.set_colorkey(BLACK)
BMP = pygame.image.load('art/trade_route00.png').convert()
(bx, by, bwidth, bheight) = route.get_rect()
route.blit(BMP, (0,0), area=route.get_rect())
# get distance within screen in pixels
dist = math.sqrt((start[0] - target[0])**2 + (start[1] - target[1])**2)
# scale to fit: use distance between points, and make width extra skinny.
route = pygame.transform.scale(route, (int(bwidth * dist/bwidth * 0.05), int( bheight * dist/bheight)))
# and rotate... (invert, as negative is for clockwise)
angle = math.degrees(math.atan2(-1*(target[1]-start[1]), target[0]-start[0]))
route = pygame.transform.rotate(route, angle + 90 )
position = route.get_rect()
HERE = (abs(target[0] - position[2]), target[1]) # - position[3]/2)
print(HERE)
screen.blit(route, HERE)
pygame.display.update()
print(start, target, dist, angle, position)

The main problem
The error is not due to the inverse y coordinates (0 at top, max at bottom) while rotating as you seems to think. That part is correct. The error is here:
HERE = (abs(target[0] - position[2]), target[1]) # - position[3]/2)
HERE must be the coordinates of the top-left corner of the rectangle inscribing your green and blue dots connected by the blue line. At those coordinates, you need to place the Surface route after rescaling.
You can get this vertex by doing:
HERE = (min(start[0], target[0]), min(start[1], target[1]))
This should solve the problem, and your colored dots should lay on the blue line.
A side note
Another thing you might wish to fix is the scaling parameter of route:
route = pygame.transform.scale(route, (int(bwidth * dist/bwidth * 0.05), int( bheight * dist/bheight)))
If my guess is correct and you want to preserve the original widht/height ratio in the rescaled route (since your original image is not a square) this should be:
route = pygame.transform.scale(route, (int(dist* bwidth/bheight), int(dist)))
assuming that you want height (the greater size in the original) be scaled to dist. So you may not need the 0.05, or maybe you can use a different shrinking parameter (probably 0.05 will shrink it too much).

How to get rect of a pygame Surface without transparent parts?

I am implementing collision detection and want to check if a rectangular object is touching the player. My wall uses .set_colorkey(background) where background is the specified background colour. The problem is that when I get my wall's rectangle with .get_rect(), it gets the full image's size which includes the transparent parts instead of just the opaque parts.
I thought about making the wall image file smaller in size to remove the background but that would be inconvenient as I would need to do this for each partially transparent image I have. I also thought about using arrays to get the colour and checking if it matches the background colour and getting the rectangle's size from there but that would be slow and cumbersome.
for x, y in ((i, j) for i in land_x for j in land_y):
# land_x, land_y hold the tiles to be checked
try:
tx1, ty1, tx2, ty2 = \
texture[land[y][x]].get_rect()
# tx1, ty1 coordinates of top-left corner
# tx2, ty2 width and height respectively
if tx2 == 0 and ty2 == 0:
continue # skip to other objects
tx1 = x*64 - tx2/2
ty1 = y*64 - ty2/2
px1, py1, px2, py2 = \
PLAYER.get_rect()
px1 = player_x - px2/2
py1 = -player_y - py2/2
if p.Rect(px1, py1, px2, py2).colliderect(
p.Rect(tx1, ty1, tx2, ty2)
):
player_x -= direction_x
break # go outside loop to start checking y
except IndexError: # incase player is outside map
pass # skip to other objects
The .get_rect() outputs a rectangle the size of the whole image whereas I want a rectangle that doesn't include the transparent parts.
Example:
texture is a 64x64 image with a 48x48 block in the centre.
The background colour is removed and a 48x48 solid coloured block is left (even though the image size is still 64x64).
Expected Output:
texture.get_rect() should output a rectangle of size 48x48.
Actual Output:
texture.get_rect() instead outputs a rectangle of size 64x64.
Any help on this would be appreciated :D

If you want to ignore the transparent pixels in your collision detection, you're talking about pixel-perfect collision.
To do this in pygame, pygame offers the Mask class. You usually create your masks with pygame.mask.from_surface and use it together with pygame.sprite.spritecollide and pygame.sprite.collide_mask.
Maybe think about using pygame's Sprite class to make use of all the features it offers.
Even if you don't want to use pygame's build-in collision detection, you can take a look at the source to see how it works.

You are making this too hard. You know the size of your objects. Add a smaller collision rect to each of your objects at creation time and use that for collision. Or use a circle if that is better for the object.
tile.crect = Rect(whatever)
Or just multiply the existing rect dimensions by some scale factor for your collision rect. Don't do all of these calculations. Store a Rect for each collideable object and have a rect for the player.
tx1 = x*64 - tx2/2
ty1 = y*64 - ty2/2
px1, py1, px2, py2 = \
PLAYER.get_rect()
px1 = player_x - px2/2
py1 = -player_y - py2/2
Then just test collision directly:
for t in tiles:
if player.rect.colliderect( t.rect ):
If the player is a sprite its rect moves around. Look at the example code in the doc.
https://www.pygame.org/docs/ref/sprite.html

Efficiently masking a surface in pygame

I need to draw a circle filled with random gray colors and a black outline using pygame. This is what it should look like:
The radius increases by expansion_speed * dt every frame and the surface is updated 60 times per second, so however this is achieved (if even possible) needs to be fast. I tried masking an stored texture but that was too slow. My next idea was to read the pixels from this stored texture and only replace the difference between the last and current surfaces. I tried this too but was unable to translate the idea to code.
So how can this be done?

See my update to your previous related question. It has some info about performance. You could try to enable hardware acceleration in fullscreen mode, but I never personally tried it, so can't give good advice how to do it properly. Just use two differnt colorkeys for extracting circle from noise and putting the whole surface to the display. Note that if your Noise surface has pixels same as colorkey color then they also become transparent.
This example I think is what you are trying to get, move the circle with mouse and hold CTRL key to change radius.
Images:
import os, pygame
pygame.init()
w = 800
h = 600
DISP = pygame.display.set_mode((w, h), 0, 24)
clock = pygame.time.Clock( )
tile1 = pygame.image.load("2xtile1.png").convert()
tile2 = pygame.image.load("2xtile2.png").convert()
tw = tile1.get_width()
th = tile1.get_height()
Noise = pygame.Surface ((w,h))
Background = pygame.Surface ((w,h))
for py in range(0, h/th + 2) :
for px in range(0, w/tw + 2):
Noise.blit(tile1, (px*(tw-1), py*(th-1) ) )
Background.blit(tile2, (px*(tw-1), py*(th-1) ) )
color_key1 = (0, 0, 0)
color_key2 = (1, 1, 1)
Circle = pygame.Surface ((w,h))
Circle.set_colorkey(color_key1)
Mask = pygame.Surface ((w,h))
Mask.fill(color_key1)
Mask.set_colorkey(color_key2)
strokecolor = (10, 10, 10)
DISP.blit(Background,(0,0))
def put_circle(x0, y0, r, stroke):
pygame.draw.circle(Mask, strokecolor, (x0,y0), r, 0)
pygame.draw.circle(Mask, color_key2, (x0,y0), r - stroke, 0)
Circle.blit(Noise,(0,0))
Circle.blit(Mask,(0,0))
dirtyrect = (x0 - r, y0 - r, 2*r, 2*r)
Mask.fill(color_key1, dirtyrect)
DISP.blit(Circle, (0,0))
X = w/2
Y = h/2
R = 100
stroke = 2
FPS = 25
MainLoop = True
pygame.mouse.set_visible(False)
pygame.event.set_grab(True)
while MainLoop :
clock.tick(FPS)
pygame.event.pump()
Keys = pygame.key.get_pressed()
MR = pygame.mouse.get_rel() # get mouse shift
if Keys [pygame.K_ESCAPE] :
MainLoop = False
if Keys [pygame.K_LCTRL] :
R = R + MR[0]
if R <= stroke : R = stroke
else :
X = X + MR[0]
Y = Y + MR[1]
DISP.blit(Background,(0,0))
put_circle(X, Y, R, stroke)
pygame.display.flip( )
pygame.mouse.set_visible(True)
pygame.event.set_grab(False)
pygame.quit( )

Many years ago we had a font rendering challenge with the Pygame project.
Someone created an animated static text for the contest but it was far too slow.
We put our heads together and made a much quicker version. Step one was to create a smallish image with random noise. Something like 64x64. You may need a bigger image if your final image is large enough to notice the tiling.
Every frame you blit the tiled noise using a random offset. Then you take an image with the mask, in your case an inverted circle, and draw that on top. That should give you a final image containing just the unmasked noise.
The results were good. In our case it was not noticeable that the noise was just jittering around. That may be because the text did not have a large unobstrcted area. I'd be concerned your large circle would make the trick appear obvious. i guess if you really had a large enough tiled image it would still work.
The results and final source code are still online at the Pygame website,
http://www.pygame.org/pcr/static_text/index.php

Generate Any number of Rects in pygame

I thought you guys might be able to help me wrap my head around this. I want to be able to generate rects and assign images to those rects. I've been doing this for the whole project and isn't too hard. The hard part here is that I want this particular function to be able to generate as many different rects as I want. The project is a game that takes place on like a chess board. I figure I can write like... if statements for every single space and then have like a bazillion parameters in the function that dictate which rects get generated and where, but I was hoping someone might be able to think of a more elegant solution.

You could use two nested "for" loops --
def make_chessboard(upper_x=0, upper_y=0, size=30):
chessboard = []
for y in range(8):
row = []
for x in range(8):
coords = (upper_x + x * size, upper_y + y * size)
row.append(pygame.Rect(coords, (size, size)))
chessboard.append(row)
return chessboard
Then, to get the rect that's in the top-left corner, you could do chessboard[0][0]. To get the rect that's in the top-right corner, you could do chessboard[0][7].
You wouldn't be able to explicitly name each rect, but then again, you really wouldn't need to.
Note: I'm assuming that you wanted to create a chessboard-like pattern of rects of some kind. I can edit my question if you detail specifically what you're trying to do.

class ChessTile(pygame.sprite.Sprite):
def __init__(self, image, location):
pygame.sprite.Sprite.__init__(self)
self.image = image.convert()
self.mask = pygame.mask.from_surface(self.image)
self.rect = pygame.Rect(location, self.image.get_size())
Then make another method called like "MakeBoard". Call MakeBoad and have a loop setup with the size of the board. so the pseudo code would be:
(let's assume "img" is a 32x32 white or black square)
for y in range(0,7):
for x in range(0,7):
# alternate the tile image from black/white before calling ChessTile with it
# the location parameter is going to be x*32,y*32.. something like that
# so you'd have a tile at (0,0) then at (32,0), then (64,0), etc...
# after the first "j" run is done, "i" increments so now we have
# (0, 32), (32, 32), etc etc.
#
tile = ChessTile(img, (x,y))
then just draw the tile object as you normall would in some render method!
hope that helps!!!