如何使用Python和pygame创建MS Paint克隆 [英] How to create MS Paint clone with Python and pygame

问题描述

如我所见，有两种方法可以处理鼠标事件以绘制图片.

As I see it, there are two ways to handle mouse events to draw a picture.

第一个是检测鼠标何时移动并在其上画一条线，如此处.但是，这样做的问题是，笔刷大小较大时，由于每条直线"都使用直线的笔触大小来创建粗线，因此它们之间的直线之间会出现许多缝隙.

The first is to detect when the mouse moves and draw a line to where the mouse is, shown here. However, the problem with this is that with a large brush size, many gaps appear between each "line" that is not straight since it is using the line's stroke size to create thick lines.

另一种方法是在鼠标移动时绘制圆，如图所示此处.这样做的问题是，如果鼠标移动的速度快于计算机检测到鼠标输入的速度，则每个圆之间都会出现间隙.

The other way is to draw circles when the mouse moves as is shown here. The problem with this is that gaps appear between each circle if the mouse moves faster than the computer detects mouse input.

以下是我的两个问题的屏幕截图:

Here's a screenshot with my issues with both:

实现像MS Paint那样的笔刷，笔刷大小相当大，在线条的笔触中没有间隙或在每个圆之间没有间隙的最佳方法是什么?

What is the best way to implement a brush like MS Paint's, with a decently-big brush size with no gaps in the stroke of the line or no gaps between each circle?

推荐答案

为什么两者都不做?

在每个端点处画一个圆，并在两者之间画一条线.

Draw a circle at each endpoint and a line between the two.

EDIT rofl，只是阻止不了我自己.

EDIT rofl, just couldn't stop myself.

实际上，您不想使用pygame.draw.line，因为它会作弊.它填充1像素宽的行或列(取决于迎角)的像素.如果确实以大致垂直的角度(0度或90度)走，这不是问题，但是在45度时，您会注意到一种四季豆效果.

Actually, you don't want to use pygame.draw.line because it cheats. It fills a 1 pixel wide row or column (depending on angle of attack) of pixels. If you do go at a roughly perpendicular angle, 0 deg or 90 deg, this isn't an issue, but at 45's, you'll notice a sort of string bean effect.

唯一的解决方案是在每个像素的距离处绘制一个圆.在这里...

The only solution is to draw a circle at every pixel's distance. Here...

import pygame, random

screen = pygame.display.set_mode((800,600))

draw_on = False
last_pos = (0, 0)
color = (255, 128, 0)
radius = 10

def roundline(srf, color, start, end, radius=1):
    dx = end[0]-start[0]
    dy = end[1]-start[1]
    distance = max(abs(dx), abs(dy))
    for i in range(distance):
        x = int( start[0]+float(i)/distance*dx)
        y = int( start[1]+float(i)/distance*dy)
        pygame.draw.circle(srf, color, (x, y), radius)

try:
    while True:
        e = pygame.event.wait()
        if e.type == pygame.QUIT:
            raise StopIteration
        if e.type == pygame.MOUSEBUTTONDOWN:
            color = (random.randrange(256), random.randrange(256), random.randrange(256))
            pygame.draw.circle(screen, color, e.pos, radius)
            draw_on = True
        if e.type == pygame.MOUSEBUTTONUP:
            draw_on = False
        if e.type == pygame.MOUSEMOTION:
            if draw_on:
                pygame.draw.circle(screen, color, e.pos, radius)
                roundline(screen, color, e.pos, last_pos,  radius)
            last_pos = e.pos
        pygame.display.flip()

except StopIteration:
    pass

pygame.quit()

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