mandelbrot.py

"""PySide6 port of the corelib/threads/mandelbrot example from Qt v5.x, originating from PyQt"""

from PySide6.QtCore import (Signal, QMutex, QMutexLocker, QPoint, QSize, Qt,
        QThread, QWaitCondition)
from PySide6.QtGui import QColor, QImage, QPainter, QPixmap, qRgb
from PySide6.QtWidgets import QApplication, QWidget


DefaultCenterX = -0.647011
DefaultCenterY = -0.0395159
DefaultScale = 0.00403897

ZoomInFactor = 0.8
ZoomOutFactor = 1 / ZoomInFactor
ScrollStep = 20


class RenderThread(QThread):
    ColormapSize = 512

    renderedImage = Signal(QImage, float)

    def __init__(self, parent=None):
        super(RenderThread, self).__init__(parent)

        self.mutex = QMutex()
        self.condition = QWaitCondition()
        self.centerX = 0.0
        self.centerY = 0.0
        self.scaleFactor = 0.0
        self.resultSize = QSize()
        self.colormap = []

        self.restart = False
        self.abort = False

        for i in range(RenderThread.ColormapSize):
            self.colormap.append(self.rgbFromWaveLength(380.0 + (i * 400.0 / RenderThread.ColormapSize)))

    def stop(self):
        self.mutex.lock()
        self.abort = True
        self.condition.wakeOne()
        self.mutex.unlock()

        self.wait(2000)

    def render(self, centerX, centerY, scaleFactor, resultSize):
        locker = QMutexLocker(self.mutex)

        self.centerX = centerX
        self.centerY = centerY
        self.scaleFactor = scaleFactor
        self.resultSize = resultSize

        if not self.isRunning():
            self.start(QThread.LowPriority)
        else:
            self.restart = True
            self.condition.wakeOne()

    def run(self):
        while True:
            self.mutex.lock()
            resultSize = self.resultSize
            scaleFactor = self.scaleFactor
            centerX = self.centerX
            centerY = self.centerY
            self.mutex.unlock()

            halfWidth = resultSize.width() // 2
            halfHeight = resultSize.height() // 2
            image = QImage(resultSize, QImage.Format_RGB32)

            NumPasses = 8
            curpass = 0

            while curpass < NumPasses:
                MaxIterations = (1 << (2 * curpass + 6)) + 32
                Limit = 4
                allBlack = True

                for y in range(-halfHeight, halfHeight):
                    if self.restart:
                        break
                    if self.abort:
                        return

                    ay = 1j * (centerY + (y * scaleFactor))

                    for x in range(-halfWidth, halfWidth):
                        c0 = centerX + (x * scaleFactor) + ay
                        c = c0
                        numIterations = 0

                        while numIterations < MaxIterations:
                            numIterations += 1
                            c = c*c + c0
                            if abs(c) >= Limit:
                                break
                            numIterations += 1
                            c = c*c + c0
                            if abs(c) >= Limit:
                                break
                            numIterations += 1
                            c = c*c + c0
                            if abs(c) >= Limit:
                                break
                            numIterations += 1
                            c = c*c + c0
                            if abs(c) >= Limit:
                                break

                        if numIterations < MaxIterations:
                            image.setPixel(x + halfWidth, y + halfHeight,
                                           self.colormap[numIterations % RenderThread.ColormapSize])
                            allBlack = False
                        else:
                            image.setPixel(x + halfWidth, y + halfHeight, qRgb(0, 0, 0))

                if allBlack and curpass == 0:
                    curpass = 4
                else:
                    if not self.restart:
                        self.renderedImage.emit(image, scaleFactor)
                    curpass += 1

            self.mutex.lock()
            if not self.restart:
                self.condition.wait(self.mutex)
            self.restart = False
            self.mutex.unlock()

    def rgbFromWaveLength(self, wave):
        r = 0.0
        g = 0.0
        b = 0.0

        if wave >= 380.0 and wave <= 440.0:
            r = -1.0 * (wave - 440.0) / (440.0 - 380.0)
            b = 1.0
        elif wave >= 440.0 and wave <= 490.0:
            g = (wave - 440.0) / (490.0 - 440.0)
            b = 1.0
        elif wave >= 490.0 and wave <= 510.0:
            g = 1.0
            b = -1.0 * (wave - 510.0) / (510.0 - 490.0)
        elif wave >= 510.0 and wave <= 580.0:
            r = (wave - 510.0) / (580.0 - 510.0)
            g = 1.0
        elif wave >= 580.0 and wave <= 645.0:
            r = 1.0
            g = -1.0 * (wave - 645.0) / (645.0 - 580.0)
        elif wave >= 645.0 and wave <= 780.0:
            r = 1.0

        s = 1.0
        if wave > 700.0:
            s = 0.3 + 0.7 * (780.0 - wave) / (780.0 - 700.0)
        elif wave < 420.0:
            s = 0.3 + 0.7 * (wave - 380.0) / (420.0 - 380.0)

        r = pow(r * s, 0.8)
        g = pow(g * s, 0.8)
        b = pow(b * s, 0.8)

        return qRgb(r*255, g*255, b*255)


class MandelbrotWidget(QWidget):
    def __init__(self, parent=None):
        super(MandelbrotWidget, self).__init__(parent)

        self.thread = RenderThread()
        self.pixmap = QPixmap()
        self.pixmapOffset = QPoint()
        self.lastDragPos = QPoint()

        self.centerX = DefaultCenterX
        self.centerY = DefaultCenterY
        self.pixmapScale = DefaultScale
        self.curScale = DefaultScale

        self.thread.renderedImage.connect(self.updatePixmap)

        self.setWindowTitle("Mandelbrot")
        self.setCursor(Qt.CrossCursor)
        self.resize(550, 400)

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.fillRect(self.rect(), Qt.black)

        if self.pixmap.isNull():
            painter.setPen(Qt.white)
            painter.drawText(self.rect(), Qt.AlignCenter,
                    "Rendering initial image, please wait...")
            return

        if self.curScale == self.pixmapScale:
            painter.drawPixmap(self.pixmapOffset, self.pixmap)
        else:
            scaleFactor = self.pixmapScale / self.curScale
            newWidth = int(self.pixmap.width() * scaleFactor)
            newHeight = int(self.pixmap.height() * scaleFactor)
            newX = self.pixmapOffset.x() + (self.pixmap.width() - newWidth) / 2
            newY = self.pixmapOffset.y() + (self.pixmap.height() - newHeight) / 2

            painter.save()
            painter.translate(newX, newY)
            painter.scale(scaleFactor, scaleFactor)
            exposed, _ = painter.transform().inverted()
            exposed = exposed.mapRect(self.rect()).adjusted(-1, -1, 1, 1)
            painter.drawPixmap(exposed, self.pixmap, exposed)
            painter.restore()

        text = "Use mouse wheel or the '+' and '-' keys to zoom. Press and " \
                "hold left mouse button to scroll."
        metrics = painter.fontMetrics()
        textWidth = metrics.horizontalAdvance(text)

        painter.setPen(Qt.NoPen)
        painter.setBrush(QColor(0, 0, 0, 127))
        painter.drawRect((self.width() - textWidth) / 2 - 5, 0, textWidth + 10,
                metrics.lineSpacing() + 5)
        painter.setPen(Qt.white)
        painter.drawText((self.width() - textWidth) / 2,
                metrics.leading() + metrics.ascent(), text)

    def resizeEvent(self, event):
        self.thread.render(self.centerX, self.centerY, self.curScale, self.size())

    def keyPressEvent(self, event):
        if event.key() == Qt.Key_Plus:
            self.zoom(ZoomInFactor)
        elif event.key() == Qt.Key_Minus:
            self.zoom(ZoomOutFactor)
        elif event.key() == Qt.Key_Left:
            self.scroll(-ScrollStep, 0)
        elif event.key() == Qt.Key_Right:
            self.scroll(+ScrollStep, 0)
        elif event.key() == Qt.Key_Down:
            self.scroll(0, -ScrollStep)
        elif event.key() == Qt.Key_Up:
            self.scroll(0, +ScrollStep)
        else:
            super(MandelbrotWidget, self).keyPressEvent(event)

    def wheelEvent(self, event):
        numDegrees = event.angleDelta().y() / 8
        numSteps = numDegrees / 15.0
        self.zoom(pow(ZoomInFactor, numSteps))

    def mousePressEvent(self, event):
        if event.buttons() == Qt.LeftButton:
            self.lastDragPos = QPoint(event.pos())

    def mouseMoveEvent(self, event):
        if event.buttons() & Qt.LeftButton:
            self.pixmapOffset += event.pos() - self.lastDragPos
            self.lastDragPos = QPoint(event.pos())
            self.update()

    def mouseReleaseEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.pixmapOffset += event.pos() - self.lastDragPos
            self.lastDragPos = QPoint()

            deltaX = (self.width() - self.pixmap.width()) / 2 - self.pixmapOffset.x()
            deltaY = (self.height() - self.pixmap.height()) / 2 - self.pixmapOffset.y()
            self.scroll(deltaX, deltaY)

    def updatePixmap(self, image, scaleFactor):
        if not self.lastDragPos.isNull():
            return

        self.pixmap = QPixmap.fromImage(image)
        self.pixmapOffset = QPoint()
        self.lastDragPosition = QPoint()
        self.pixmapScale = scaleFactor
        self.update()

    def zoom(self, zoomFactor):
        self.curScale *= zoomFactor
        self.update()
        self.thread.render(self.centerX, self.centerY, self.curScale,
                self.size())

    def scroll(self, deltaX, deltaY):
        self.centerX += deltaX * self.curScale
        self.centerY += deltaY * self.curScale
        self.update()
        self.thread.render(self.centerX, self.centerY, self.curScale,
                self.size())


if __name__ == '__main__':

    import sys

    app = QApplication(sys.argv)
    widget = MandelbrotWidget()
    widget.show()
    r = app.exec_()
    widget.thread.stop()
    sys.exit(r)