画线：检索覆盖的像素

Question

我想在一个小部件上画一条线：

from PyQt4 import QtGui, QtCore

class LineLabel(QtGui.QLabel):

    def __init__(self,parent=None):
        super(LineLabel,self).__init__(parent)
        self.setMinimumSize(100,100)
        self.setMaximumSize(100,100)

    def paintEvent(self,e):
        painter=QtGui.QPainter(self)
        pen = QtGui.QPen()
        pen.setWidth(5)
        painter.setPen(pen)
        painter.drawLine(10,10,90,90)
        painter.end()

def test():
    form = QtGui.QWidget()
    label = LineLabel(form)
    form.show()
    return form

import sys
app = QtGui.QApplication(sys.argv)
window =test()
sys.exit(app.exec_())

获取线所覆盖的像素列表的最佳方法是什么？

来自 cmets 的更新：

• 我不需要直接知道起点和终点之间的像素，而是所有那些变为黑色的像素（因为线条有一定宽度，所以像素更多）。
• 我的总体目标是快速了解小部件上的哪些像素是黑色的。迭代图像的像素并查询颜色比从存储颜色的列表中读取颜色值要慢得多：对我来说，100 万像素的图像需要 1.9 秒，而 100 万条目的列表需要 0.23 秒.因此，每次更改小部件上的图像后，我必须更新该列表，例如画一条线。
• 在 QGraphicsScene 中引用 QGraphicsItem 的答案也很有帮助。

Answer 1

您可以使用线性方程在直线中找到您想要的点。我认为没有提到画线。

from PyQt4 import QtGui
from PyQt4.QtGui import QColor, QPaintEvent

m_nInitialX = 0.0
m_nInitialY = 0.0


# my line abstraction
class MyLine:
    x1, y1, x2, y2 = .0, .0, .0, .0
    width = .0
    px, py = (.0, .0)
    draw_point = False

    def __init__(self, x1, y1, x2, y2, width):
        self.x1, self.y1, self.x2, self.y2 = (x1, y1, x2, y2)
        self.width = width

    def is_in_line(self, x, y):
        # mark a position in the line
        m = (self.y2 - self.y1) / (self.x2 - self.x1)
        print(m*(x-self.x1)-(y-self.y1))
        if abs((m*(x-self.x1) - (y-self.y1))) <= self.width/2:
            self.draw_point = True
            return True
        else:
            return False

    def add_red_point(self, x, y):
        self.px, self.py = (x, y)

    def draw(self, widget):
        painter = QtGui.QPainter(widget)
        pen = QtGui.QPen()
        pen.setWidth(self.width)
        painter.setPen(pen)
        painter.drawLine(self.x1, self.y1, self.y2, self.y2)

        if self.draw_point:
            pen.setColor(QColor(255, 0, 0))
            painter.setPen(pen)
            painter.drawPoint(self.px, self.py)
        painter.end()


line = MyLine(10, 10, 90, 90, width=10)  # <-- my line abstraction


class LineLabel(QtGui.QLabel):

    def __init__(self, parent=None):
        super(LineLabel, self).__init__(parent)
        self.setMinimumSize(100, 100)
        self.setMaximumSize(100, 100)

    # always redraw when needed
    def paintEvent(self, e):
        print("draw!")
        line.draw(self)

    def mousePressEvent(self, event):
        # mark clicked position in line
        m_nInitialX = event.pos().x()
        m_nInitialY = event.pos().y()
        if line.is_in_line(m_nInitialX, m_nInitialY):
            line.add_red_point(m_nInitialX, m_nInitialY)
            self.repaint()


def test():
    form = QtGui.QWidget()
    label = LineLabel(form)
    form.show()
    return form

import sys

app = QtGui.QApplication(sys.argv)
window = test()
sys.exit(app.exec_())