How to zoom a picture implemented with QPixmap on pyqt5

Question

I am trying to zoom in a picture i implemented with QPixmap but nothing works. Here is the way i implemented this. (self.hauteur is a float that represents the height)

self.label.setPixmap(QPixmap(self.image).scaledToHeight(self.hauteur))

I've put my label into a layout in order to put it in a scroll widget then.

self.layout6.addWidget(self.label)

...

self.widget1=QWidget()
    self.widget1.setLayout(self.layout6)
    self.scroll1.setWidget(self.widget1)
    self.tab1.layout.addWidget(self.scroll1,0,1,1,2)

...

self.tab1.setLayout(self.tab1.layout)

How should I do if i want to build a method that zoom in or zoom out the picture in my window by pushing a button ? I've tried to resize the label but it doesn't work.

self.action5=QAction(QIcon("Icon/in"),"Zoom in",self)
    self.action5.triggered.connect(self.zoomin)

...

 def zoomin(self):
    self.hauteur+=100
    self.label.scaledToHeight(self.hauteur)
    self.update()

The code you have provided is not an MRE, please read the link — eyllanesc, Jun 12 '20 at 16:41
you try to scale label but probably you have to scale original image `QPixmap` and put it in label again (to replace previous image). — furas, Jun 12 '20 at 20:19

furas · Accepted Answer · 2020-06-12T21:41:30.657

I would resize original QPixmap and put it again in label

    self.scale *= 2

    size = self.pixmap.size()

    scaled_pixmap = self.pixmap.scaled(self.scale * size)

    self.label.setPixmap(scaled_pixmap)

Minimal working code:

from PyQt5.QtWidgets import *
from PyQt5.QtGui import *

class MyApp(QWidget):

    def __init__(self, *args):
        super().__init__(*args)

        self.layout = QVBoxLayout()
        self.setLayout(self.layout)

        self.button_zoom_in = QPushButton('Zoom IN', self)
        self.button_zoom_in.clicked.connect(self.on_zoom_in)
        self.layout.addWidget(self.button_zoom_in)

        self.button_zoom_out = QPushButton('Zoom OUT', self) 
        self.button_zoom_out.clicked.connect(self.on_zoom_out)
        self.layout.addWidget(self.button_zoom_out)

        self.pixmap = QPixmap('image.jpg')

        self.label = QLabel(self)
        self.label.setPixmap(self.pixmap)
        self.layout.addWidget(self.label)

        self.scale = 1

        self.show()

    def on_zoom_in(self, event):
        self.scale *= 2
        self.resize_image()

    def on_zoom_out(self, event):
        self.scale /= 2
        self.resize_image()

    def resize_image(self):
        size = self.pixmap.size()

        scaled_pixmap = self.pixmap.scaled(self.scale * size)

        self.label.setPixmap(scaled_pixmap)

# --- main ---

app = QApplication([])
win = MyApp()
app.exec()

EDIT: The same using self.height += 100 instead of self.scale *= 2

from PyQt5.QtWidgets import *
from PyQt5.QtGui import *

class MyApp(QWidget):

    def __init__(self, *args):
        super().__init__(*args)

        self.layout = QVBoxLayout()
        self.setLayout(self.layout)

        self.button_zoom_in = QPushButton('Zoom IN', self)
        self.button_zoom_in.clicked.connect(self.on_zoom_in)
        self.layout.addWidget(self.button_zoom_in)

        self.button_zoom_out = QPushButton('Zoom OUT', self) 
        self.button_zoom_out.clicked.connect(self.on_zoom_out)
        self.layout.addWidget(self.button_zoom_out)

        self.pixmap = QPixmap('image.jpg')
        self.height = self.pixmap.height()

        self.label = QLabel(self)
        self.label.setPixmap(self.pixmap)
        self.layout.addWidget(self.label)

        self.show()

    def on_zoom_in(self, event):
        self.height += 100
        self.resize_image()

    def on_zoom_out(self, event):
        self.height -= 100
        self.resize_image()

    def resize_image(self):
        scaled_pixmap = self.pixmap.scaledToHeight(self.height)
        self.label.setPixmap(scaled_pixmap)

# --- main ---

app = QApplication([])
win = MyApp()
app.exec()

How to zoom a picture implemented with QPixmap on pyqt5

1 Answers1