PyQt5实现画布小程序

本文实例为大家分享了PyQt5实现画布小程序的具体代码，供大家参考，具体内容如下

实现的效果图如下：

该实例中，涉及到的知识点有：

1.PyQt5 的常用的布局方式，这里使用到了QVBoxLayout，QHBoxLayout，如何灵活运用这些布局；

2.常用组件的使用方法，这里使用到了QPushButton, QLabel, QPixmap；

3.使用QPainter进行绘制；

4.事件与槽；

主要代码如下：

import random
import sys

from PyQt5.QtCore import QSize
from PyQt5.QtGui import QPixmap, QPainter, QColor
from PyQt5.QtWidgets import QMainWindow, QLabel, QApplication, QPushButton, QWidget, QVBoxLayout, QHBoxLayout

SPRAY_PARTICLES = 100
SPRAY_DIAMMETER = 10

COLORS = [
  '#000000', '#141923', '#414168', '#3a7fa7', '#35e3e3', '#8fd970', '#5ebb49',
  '#458352', '#dcd37b', '#fffee5', '#ffd035', '#cc9245', '#a15c3e', '#a42f3b',
  '#f45b7a', '#c24998', '#81588d', '#bcb0c2', '#ffffff',
]

class QPlatteButton(QPushButton):
  def __init__(self, color):
    super().__init__()

    self.setFixedSize(QSize(24, 24))
    self.color = color
    self.setStyleSheet("background-color: %s" % self.color)

class Canvas(QLabel):
  def __init__(self):
    super().__init__()

    canvas = QPixmap(1200, 800)
    canvas.fill(QColor('white'))
    self.setPixmap(canvas)

    self.last_x, self.last_y = None, None
    self.pen_color = QColor('#000')

  def set_pen_color(self, c):
    self.pen_color = QColor(c)

  def mouseReleaseEvent(self, *args, **kwargs):
    """
    松开鼠标事件
    """
    self.last_x, self.last_y = None, None

  def mouseMoveEvent(self, e):
    """
    移动鼠标事件
    """
    if self.last_x is None:
      self.last_x = e.x()
      self.last_y = e.y()
      return

    painter = QPainter(self.pixmap())
    pen = painter.pen()
    pen.setWidth(4)
    pen.setColor(self.pen_color)
    painter.setPen(pen)
    painter.drawLine(self.last_x, self.last_y, e.x(), e.y())
    painter.end()
    self.update()

    # update the origin for next time
    self.last_x = e.x()
    self.last_y = e.y()

  # def mouseMoveEvent(self, e):
  #   painter = QPainter(self.pixmap())
  #   p = painter.pen()
  #   p.setWidth(1)
  #   p.setColor(self.pen_color)
  #   painter.setPen(p)
  #
  #   for n in range(SPRAY_PARTICLES):
  #     xo = random.gauss(0, SPRAY_DIAMMETER)
  #     yo = random.gauss(0, SPRAY_DIAMMETER)
  #     painter.drawPoint(e.x() + xo, e.y() + yo)
  #
  #   self.update()

class MainWindow(QMainWindow):
  def __init__(self):
    super().__init__()
    self.setWindowTitle("画板小程序")

    self.canvas = Canvas()

    widget = QWidget()
    vlayout = QVBoxLayout()
    widget.setLayout(vlayout)

    vlayout.addWidget(self.canvas)

    palette = QHBoxLayout()
    vlayout.addLayout(palette)
    self.add_palette_buttons(palette)
    self.setCentralWidget(widget)

  def add_palette_buttons(self, layout):
    """
    在水平布局中放入一行调色板
    """
    for c in COLORS:
      b = QPlatteButton(c)
      b.pressed.connect(lambda c=c: self.canvas.set_pen_color(c))
      layout.addWidget(b)

if __name__ == '__main__':
  app = QApplication(sys.argv)
  window = MainWindow()
  window.move(120, 120)
  window.show()
  app.exec_()

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