Qslider won't pass parameter in PyQt5

Question

my function won't work when the slider value changed i don't know why ? it's my first time using PyQt5.

from PIL.ImageQt import Image, ImageQt
from PIL import ImageEnhance

from PyQt5.QtWidgets import (QApplication, QDialog, QGridLayout,
                             QLabel, QPushButton, QGroupBox,
                             QSlider, QVBoxLayout, QFileDialog)
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPixmap, QIcon


class MainWindow(QDialog):
    def __init__(self):
        super(MainWindow,self).__init__()

        self.originalPalette = QApplication.palette()
#        self.setAcceptDrops(True)

        self.createTopGroupBox()
        self.createBottomGroupBox()
#        self.color("blue")

        mainLayout = QGridLayout()
        mainLayout.addWidget(self.topGroupBox, 0, 0)
        mainLayout.addWidget(self.bottomGroupBox, 1, 0)        
        #mainLayout.setRowStretch(1, 1)
        #mainLayout.setRowStretch(2, 1)
        #mainLayout.setColumnStretch(0, 1)
        #mainLayout.setColumnStretch(1, 1)
        self.setLayout(mainLayout)

        self.setWindowTitle("Photo Editor")    
        self.resize(800, 800)

    def createTopGroupBox(self):  

        self.topGroupBox = QGroupBox()
        openImgButton = QPushButton("Open Image")
        openImgButton.clicked.connect(self.getImage)
        self.label = QLabel("Your Photo")

        layout = QVBoxLayout()
        layout.addWidget(openImgButton)
        layout.addWidget(self.label)
        layout.addStretch(1)
        self.topGroupBox.setLayout(layout)

    def getImage(self):
        global fname
        fname = QFileDialog.getOpenFileName(self, 'Open file',
               'c:\ ', "Image files (*.jpeg *.jpg *.gif *.bmp *.png))")
        imagePath = fname[0]
        #pixmap = QPixmap(imagePath)
        self.image = Image.open(imagePath)
        self.qimage = ImageQt(self.image)
        self.label.setPixmap(QPixmap.fromImage(self.qimage))
        self.resize(self.qimage.width(), self.qimage.height())

    def createBottomGroupBox(self):

        self.bottomGroupBox = QGroupBox()

        self.sliderBrightness = QSlider(Qt.Horizontal, self)
        brightnessLabel = QLabel("Brightness:")
        brightnessLabel.setBuddy(self.sliderBrightness)
        self.sliderBrightness.setTickPosition(QSlider.TicksBelow)
        self.sliderBrightness.setTickInterval(1)
        self.sliderBrightness.setValue(100)
        self.sliderBrightness.setMinimum(0)
        self.sliderBrightness.setMaximum(200)
        self.brightnessValueLabel = QLabel("1")

        self.sliderContrast = QSlider(Qt.Horizontal, self)
        contrastLabel = QLabel("Contrast:")
        contrastLabel.setBuddy(contrastLabel)
        self.sliderContrast.setValue(1)
        self.sliderContrast.setMinimum(0)
        self.sliderContrast.setMaximum(2)
        self.contrastValueLabel = QLabel("1")

        sliderSharpness = QSlider(Qt.Horizontal, self)
        sharpnessLabel = QLabel("Sharpness:")
        sharpnessLabel.setBuddy(sharpnessLabel)
        sliderSharpness.setValue(1)
        sliderSharpness.setMinimum(0)
        sliderSharpness.setMaximum(2)
        self.sharpnessValueLabel = QLabel("1")

        savePushButton = QPushButton("Save")
        savePushButton.clicked.connect(self.saveImage("image.png", "PNG"))

        self.sliderBrightness.valueChanged.connect(self.valueChangeBrightness)
        self.sliderContrast.valueChanged.connect(self.valueChangeContrast)
        sliderSharpness.valueChanged.connect(self.valueChangeSharpness)

        layout = QVBoxLayout()
        layout.addWidget(brightnessLabel)
        layout.addWidget(self.sliderBrightness, 0)
        layout.addWidget(self.brightnessValueLabel)
        layout.addWidget(contrastLabel)
        layout.addWidget(self.sliderContrast, 1)
        layout.addWidget(sharpnessLabel)
        layout.addWidget(sliderSharpness, 2)
        layout.addWidget(savePushButton, 3)
        self.bottomGroupBox.setLayout(layout)

    def saveImage(self, fileName, fileFormat):
        self.editImage.save(fileName, fileFormat)            

    def valueChangeBrightness(self, sliderValue):

        factor = float(sliderValue)/100
        enhancer_object = ImageEnhance.Brightness(self.image)
        self.editImage = enhancer_object.enhance(factor)
        self.brightnessValueLabel.setText(str(self.sliderBrightness.value()))       

    def valueChangeContrast(self, factor):

        enhancer_object = ImageEnhance.Contrast(self.image)
        enhancer_object.enhance(factor)

    def valueChangeSharpness(self, factor):

        enhancer_object = ImageEnhance.Sharpness(self.image)
        enhancer_object.enhance(factor)


if __name__ == '__main__':

    import sys

    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())

With the code you provide it is impossible to know why the brightness change does not work. Note that the problem of brightness change can have several sources: 1) The change is not applied, 2) even if the change is applied it is not shown in the GUI (if you want to show it), etc. If you want help then you must provide an MRE. — eyllanesc, Jan 25 '20 at 19:58

score 0 · Answer 1 · answered Jan 26 '20 at 16:11

The main problem in the OP code is that it has not updated the image shown. For example, if the docs is reviewed, it is understood that the enhance method returns the modified image but is neither saved nor displayed.

On the other hand the application of the changes must be in cascade (one behind the other).

There are also errors such as not verifying that the filename is an empty string, in addition that the clicked signal is connected to a shutdown, not to which an evaluated function returns.

Considering the above, the solution is:

from PIL.ImageQt import Image, ImageQt
from PIL import ImageEnhance

from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPixmap
from PyQt5.QtWidgets import (
    QApplication,
    QDialog,
    QGridLayout,
    QLabel,
    QPushButton,
    QGroupBox,
    QSlider,
    QVBoxLayout,
    QFileDialog,
)


class MainWindow(QDialog):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.createTopGroupBox()
        self.createBottomGroupBox()
        mainLayout = QGridLayout(self)
        mainLayout.addWidget(self.topGroupBox, 0, 0)
        mainLayout.addWidget(self.bottomGroupBox, 1, 0)

        self.setWindowTitle("Photo Editor")
        self.resize(800, 800)

        self.input_image = None
        self.output_image = None

    def createTopGroupBox(self):
        self.topGroupBox = QGroupBox()
        openImgButton = QPushButton("Open Image")
        openImgButton.clicked.connect(self.getImage)
        self.label = QLabel("Your Photo")

        layout = QVBoxLayout()
        layout.addWidget(openImgButton)
        layout.addWidget(self.label)
        layout.addStretch(1)
        self.topGroupBox.setLayout(layout)

    def getImage(self):
        fname, _ = QFileDialog.getOpenFileName(
            self, "Open file", "", "Image files (*.jpeg *.jpg *.gif *.bmp *.png)"
        )
        if fname:
            self.input_image = Image.open(fname)
            self.show_image(self.input_image)

    def show_image(self, image):
        qimage = ImageQt(image)
        self.label.setPixmap(QPixmap.fromImage(qimage))

    def createBottomGroupBox(self):
        self.bottomGroupBox = QGroupBox()
        self.sliderBrightness = QSlider(
            Qt.Horizontal,
            tickPosition=QSlider.TicksBelow,
            tickInterval=1,
            value=100,
            minimum=0,
            maximum=200,
        )
        brightnessLabel = QLabel("Brightness:")
        brightnessLabel.setBuddy(self.sliderBrightness)

        self.brightnessValueLabel = QLabel()
        self.brightnessValueLabel.setNum(self.sliderBrightness.value())

        self.sliderContrast = QSlider(Qt.Horizontal, value=1, minimum=0, maximum=2)
        contrastLabel = QLabel("Contrast:")
        contrastLabel.setBuddy(self.sliderContrast)
        self.contrastValueLabel = QLabel()
        self.contrastValueLabel.setNum(self.sliderContrast.value())

        self.sliderSharpness = QSlider(Qt.Horizontal, value=1, minimum=0, maximum=2)
        sharpnessLabel = QLabel("Sharpness:")
        sharpnessLabel.setBuddy(self.sliderSharpness)
        self.sharpnessValueLabel = QLabel()
        self.sharpnessValueLabel.setNum(self.sliderSharpness.value())

        savePushButton = QPushButton("Save")
        savePushButton.clicked.connect(lambda: self.saveImage("image.png", "PNG"))

        self.sliderBrightness.valueChanged.connect(self.update_image)
        self.sliderContrast.valueChanged.connect(self.update_image)
        self.sliderSharpness.valueChanged.connect(self.update_image)

        layout = QVBoxLayout()
        layout.addWidget(brightnessLabel)
        layout.addWidget(self.sliderBrightness)
        layout.addWidget(self.brightnessValueLabel)

        layout.addWidget(contrastLabel)
        layout.addWidget(self.sliderContrast)
        layout.addWidget(self.contrastValueLabel)

        layout.addWidget(sharpnessLabel)
        layout.addWidget(self.sliderSharpness)
        layout.addWidget(self.sharpnessValueLabel)

        layout.addWidget(savePushButton)
        self.bottomGroupBox.setLayout(layout)

    def saveImage(self, fileName, fileFormat):
        if self.output_image is not None:
            self.output_image.save(fileName, fileFormat)

    def update_image(self):
        if self.input_image is not None:
            factor_brightness = self.sliderBrightness.value() / 100.0
            factor_contrast = self.sliderContrast.value()
            factor_sharpness = self.sliderSharpness.value()

            enhancer_object = ImageEnhance.Brightness(self.input_image)
            image = enhancer_object.enhance(factor_brightness)
            enhancer_object = ImageEnhance.Contrast(image)
            image = enhancer_object.enhance(factor_contrast)
            enhancer_object = ImageEnhance.Sharpness(image)
            self.output_image = enhancer_object.enhance(factor_sharpness)
            self.show_image(self.output_image)


if __name__ == "__main__":

    import sys

    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())

Qslider won't pass parameter in PyQt5

1 Answers1