如何让pygame在两点之间的直线上绘制所有点？

Question

我正在尝试创建一个画笔函数，使用毛笔的书法风格在画布上绘制，一边细一边粗。目前，画笔印迹的实际绘制已经可以工作，但代码运行速度不够快，导致实际线条断断续续（如动态图所示）。

这是我目前的代码：

import pygame
import os
import random
from pygame.locals import *

flags = DOUBLEBUF

pygame.init()
pygame.event.set_allowed([QUIT])

current_path = os.path.dirname(__file__) #The directory the main file is in
iconPath = os.path.join(current_path, 'images') #The icon folder path

displayWidth = 1280
displayHeight = 720

gameDisplay = pygame.display.set_mode((displayWidth, displayHeight), flags)
gameDisplay.set_alpha(None)
pygame.display.set_caption('PyPaint')

black = (0, 0, 0)
white = (255, 255, 255)
grey = (200, 200, 200)
cyan = (0, 200, 255)
green = (0, 150, 0)
lightGreen = (0, 255, 0)
red = (150, 0, 0)
lightRed = (255, 0, 0)

smallfont = pygame.font.SysFont("arial", 40)
medfont = pygame.font.SysFont("arial", 60)
largefont = pygame.font.SysFont("arial", 80)

airbrushIcon = pygame.image.load(os.path.join(iconPath, "airbrush.png"))
pencilIcon = pygame.image.load(os.path.join(iconPath, "pencil.png"))
calligraphyIcon = pygame.image.load(os.path.join(iconPath, "calligraphy.png"))
eraserIcon = pygame.image.load(os.path.join(iconPath, "eraser.png"))

clock = pygame.time.Clock()
FPS = 60

airbrushMode = False
calligraphyMode = False
eraserMode = False

def paintScreen():
    global airbrushMode
    global calligraphyMode
    global eraserMode
    airbrushMode = False
    paint = True
    gameDisplay.fill(cyan)
    message_to_screen('Welcome to PyPaint', black, -300, 'large')
    click = pygame.mouse.get_pressed()
    pygame.draw.rect(gameDisplay, white, (50, 120, displayWidth - 100, displayHeight - 240))
    while paint:
        cur = pygame.mouse.get_pos()
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                quit()

        button('X', 20, 20, 50, 50, red, lightRed, action = 'quit')
        icon(airbrushIcon, white, 50, displayHeight - 101, 51, 51, white, grey, 'airbrush')
        icon(pencilIcon, white, 140, displayHeight - 101, 51, 51, white, grey, 'pencil')
        icon(calligraphyIcon, white, 230, displayHeight - 101, 51, 51, white, grey, 'calligraphy')
        icon(eraserIcon, white, 320, displayHeight - 101, 51, 51, white, grey, 'eraser')
        pygame.draw.rect(gameDisplay, cyan, (0, 120, 50, displayHeight - 100))#to clean up the left border of the canvas
        pygame.draw.rect(gameDisplay, cyan, (displayWidth - 50, 120, 50, displayHeight - 100))#to clean up the right border of the canvas
        pygame.draw.rect(gameDisplay, cyan, (0, displayHeight - 120, displayWidth, 20))#to clean up the bottom of the canvas
        pygame.draw.rect(gameDisplay, cyan, (0, 100, displayWidth, 20))#to clean up the top of the canvas
        if airbrushMode == True:
            airbrush()
        elif calligraphyMode == True:
            calligraphy()
        elif eraserMode == True:
            eraser()
        pygame.display.update()

def icon(icon, colour, x, y, width, height, inactiveColour, activeColour, action = None):
    global airbrushMode
    global calligraphyMode
    global eraserMode
    cur = pygame.mouse.get_pos()
    click = pygame.mouse.get_pressed()
    if x + width > cur[0] > x and y + height > cur[1] > y:#if the cursor is over the button
        pygame.draw.rect(gameDisplay, activeColour, (x, y, width, height))
        gameDisplay.blit(icon, (x, y))
        if click[0] == 1 and action != None: #if clicked
            if action == 'quit':
                pygame.quit()
                quit()
            elif action == 'pencil':
                pencilMode = True
                airbrushMode = False
                calligraphyMode = False
                eraserMode = False
            elif action == 'airbrush':
                airbrushMode = True
                calligraphyMode = False
                pencilMode = False
                eraserMode = False
            elif action == 'calligraphy':
                calligraphyMode = True
                airbrushMode = False
                pencilMode = False
                eraserMode = False
            elif action == 'eraser':
                eraserMode = True
                airbrushMode = False
                pencilMode = False
                calligraphyMode = False
    else:
        pygame.draw.rect(gameDisplay, inactiveColour, (x, y, width, height))
        gameDisplay.blit(icon, (x, y))

def button(text, x, y, width, height, inactiveColour, activeColour, action = None):
    cur = pygame.mouse.get_pos()
    click = pygame.mouse.get_pressed()
    if x + width > cur[0] > x and y + height > cur[1] > y:
        pygame.draw.rect(gameDisplay, activeColour, (x, y, width, height))
        if click[0] == 1 and action != None:
            if action == 'quit':
                pygame.quit()
                quit()
    else:
        pygame.draw.rect(gameDisplay, inactiveColour, (x, y, width, height))
    text_to_button(text, black, x, y, width, height)

def text_to_button(msg, colour, buttonx, buttony, buttonwidth, buttonheight, size = 'small'):
    textSurf, textRect = text_objects (msg, colour, size)
    textRect.center = ((buttonx + (buttonwidth/2)), buttony + (buttonheight/2))
    gameDisplay.blit(textSurf, textRect)

def message_to_screen(msg, colour, y_displace = 0, size = 'small'):
    textSurf, textRect = text_objects (msg, colour, size)
    textRect.center = (displayWidth / 2), (displayHeight / 2) + y_displace
    gameDisplay.blit(textSurf, textRect)

def airbrush(brushSize = 3):
    cur = pygame.mouse.get_pos()
    click = pygame.mouse.get_pressed()
    if cur[0] >= 50 and cur[0] <= displayWidth - 50 and cur[1] >= 120 and cur[1] <= displayHeight - 120:
        if click[0] == 1:
            pygame.draw.circle(gameDisplay, black, (cur[0] + random.randrange(-brushSize * 2, brushSize * 2), cur[1] + random.randrange(-brushSize * 2, brushSize * 2)), random.randrange(1, brushSize * 2))

def calligraphy(brushSize = 3):
    cur = pygame.mouse.get_pos()
    click = pygame.mouse.get_pressed()
    if cur[0] >= 50 and cur[0] <= displayWidth - 50 and cur[1] >= 120 and cur[1] <= displayHeight - 120:#if cursor is on the canvas
        if click[0] == 1:
            pygame.draw.rect(gameDisplay, black, (cur[0] - brushSize / 2, cur[1] - brushSize / 4, brushSize, brushSize * 3))

def eraser(brushSize = 3):
    cur = pygame.mouse.get_pos()
    click = pygame.mouse.get_pressed()
    if cur[0] >= 50 and cur[0] <= displayWidth - 50 and cur[1] >= 120 and cur[1] <= displayHeight - 120:#if cursor is on the canvas
        if click[0] == 1:
            pygame.draw.rect(gameDisplay, white, (cur[0] - brushSize / 2, cur[1] - brushSize / 2, brushSize * 6, brushSize * 6))

def text_objects(text, colour, size):
    if size == 'small':
        textSurface = smallfont.render (text, True, colour)
    elif size == 'medium':
        textSurface = medfont.render (text, True, colour)
    elif size == 'large':
        textSurface = largefont.render (text, True, colour)
    return textSurface, textSurface.get_rect() 

paintScreen()

我尝试在几个不同的函数中添加clock.tick()以尽可能快地运行它，但它仍然以相同的方式切割。我甚至在一台更新、更快的计算机上进行了测试，也没有任何区别，这意味着问题在于python而不是计算机。如何让pygame在两点之间的所有点上绘制线条？

- Normy Haddad

---

绘制两点之间的直线而不是所有点。 - furas

https://dev59.com/cF_Va4cB1Zd3GeqPR0z9 - Rockybilly

你需要计算两点之间的所有点并将它们绘制出来 - 这不应该很难。使用 max(x2-x1, y2-y1) 计算出需要的步数 - 也就是你需要绘制多少个点。在每一步中，你需要移动 (x2-x1)/steps 和 (y2-y1)/steps。为了得到更平滑的线条，可能需要使用浮点值来保持 (x,y) 坐标。 - furas

由于我无法发布我的答案。使用Bresenham算法（或其他算法）计算前一个鼠标位置和当前位置之间的点列表。然后，在该线路的每个位置上，根据所使用的工具绘制正确的基元。不过，喷枪仍然会有些棘手。- https://en.wikipedia.org/wiki/Bresenham's_line_algorithm - Kingsley

是的，自至少1981年（当我在学校里遇到它时）以来，Bresenham算法一直是这类应用程序的标准。 - Prune

Answer 1

我用我的评论中提到的方法创建了一个最小化的工作示例。

我记住了前一个点（或无）以绘制新点和前一个点之间的缺失点。

我计算要添加多少点。

steps = max(abs(x-prev_x), abs(y-prev_y))

和点之间的距离

dx = (x - prev_x)/steps
dy = (y - prev_y)/steps

然后我可以循环绘制缺失的点。

for _ in range(steps):
    prev_x += dx
    prev_y += dy
    pygame.draw.circle(display, BLACK, (round(prev_x - 5), round(prev_y - 5)), 10)

完整的代码

import pygame

# --- constants --- (uppercase)
BLACK = (  0,   0,   0)
WHITE = (255, 255, 255)

WIDTH = 800
HEIGHT = 600
FPS = 60

# --- functions --- (lowercase)

def airbrush(brushSize = 3):
    global prev_x
    global prev_y

    click = pygame.mouse.get_pressed()
    if click[0] == 1:
        x, y = pygame.mouse.get_pos()
        if x >= 0 and x <= WIDTH and y >= 0 and y <= HEIGHT0:
            pygame.draw.circle(display, BLACK, (x - 5, y - 5), 10)

        # if there is previous point then draw missing points 
        if prev_x is not None:
            diff_x = x - prev_x
            diff_y = y - prev_y
            steps = max(abs(diff_x), abs(diff_y))

            # skip if distance is zero (error: dividing by zero)
            if steps > 0:
                dx = diff_x / steps
                dy = diff_y / steps
                for _ in range(steps):
                    prev_x += dx
                    prev_y += dy
                    pygame.draw.circle(display, BLACK, (round(prev_x - 5), round(prev_y - 5)), 10)
        prev_x = x # remeber previous point
        prev_y = y # remeber previous point
    else:
        prev_x = None # there is no previous point
        prev_y = None # there is no previous point

# --- main ---

pygame.init()

display = pygame.display.set_mode((WIDTH, HEIGHT), pygame.DOUBLEBUF)

prev_x = None # at start there is no previous point
prev_y = None # at start there is no previous point

display.fill(WHITE)
clock = pygame.time.Clock()

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            quit()

    airbrush()
    pygame.display.update()
    clock.tick(FPS)

如果你删除这些行。

prev_x = x
prev_y = y

然后您将获得没有丢失点的版本。

- furas