pyqt/paint_app.py

import random
import sys

from PyQt5 import QtWidgets, QtGui, QtCore

COLORS = [
    # 17undertoneshttps://lospec.com/palette-list/17undertones
    '#000000', '#141923', '#414168', '#3A7FA7', '#35E3E3', '#8FD970', '#5EBB49',
    '#458352', '#DCD37B', '#FFFEE5', '#FFD035', '#CC9245', '#A15C3E', '#A42F3B',
    '#F45B7A', '#C24998', '#81588D', '#BCB0C2', '#FFFFFF', ]
SPRAY_PARTICLES = 100
SPRAY_DIAMMETER = 10


class Canvas(QtWidgets.QLabel):
    def __init__(self):
        super().__init__()
        pixmap = QtGui.QPixmap(600, 300)
        self.setPixmap(pixmap)

        self.last_x, self.last_y = None, None
        self.pen_color = QtGui.QColor('#000000')

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

    def mouseMoveEvent(self, e):
        if self.last_x is None:
            self.last_x = e.x()
            self.last_y = e.y()
            return

        painter = QtGui.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()

        self.last_x = e.x()
        self.last_y = e.y()

    def mouseReleaseEvent(self, e):
        self.last_x, self.last_y = None, None


class QPaletteButton(QtWidgets.QPushButton):
    def __init__(self, color):
        super().__init__()
        self.setFixedSize(QtCore.QSize(24, 24))
        self.color = color
        self.setStyleSheet("background-color: %s;" % color)


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()

        self.canvas = Canvas()

        w = QtWidgets.QWidget()
        l = QtWidgets.QVBoxLayout()
        w.setLayout(l)
        l.addWidget(self.canvas)

        palette = QtWidgets.QHBoxLayout()
        self.add_palette_buttons(palette)
        l.addLayout(palette)

        self.setCentralWidget(w)

    def add_palette_buttons(self, layout):
        for c in COLORS:
            b = QPaletteButton(c)
            b.pressed.connect(lambda color=c: self.canvas.set_pen_color(color))
            layout.addWidget(b)


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