PyQt5 rotation pixmap - pyqt5

Question

In Pyqt5 I want to rotate a pixmap but every time i tried it changes the size.
My code is:
import math
import sys
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QPushButton, QLabel
from PyQt5.QtCore import QObject, QPointF, Qt, QRectF,QRect
from PyQt5.QtGui import QPixmap, QTransform, QPainter
class Window(QWidget):
def __init__(self, *args, **kwargs):
super(Window, self).__init__()
self.arch1 = QPixmap("arch1.png")
pm = QPixmap(556,556)
rectF = QRectF(0,0,556,556)
painter = QPainter(pm)
painter.drawPixmap(rectF, self.arch1, rectF)
painter.end()
self.label = QLabel("AAAAAAAAAA")
self.label.setPixmap(pm)
butA = QPushButton("A")
butA.clicked.connect(lambda: self.rotate_item())
layout = QVBoxLayout()
layout.addWidget(self.label)
layout.addWidget(butA)
self.setLayout(layout)
self.show()
def rotate_item(self):
rectF = QRectF(0,0,556,556)
self.arch1 = self.arch1.transformed(QTransform().rotate(36))
pix = QPixmap(556,556)
painter = QPainter(pix)
painter.drawPixmap(rectF, self.arch1,QRectF(self.arch1.rect()))
painter.end()
self.label.setPixmap(pix)
def main():
app = QApplication(sys.argv)
window = Window()
window.show()
sys.exit(app.exec_())
if __name__=="__main__":
main()
I want only rotate not resize. What do you suggest me to do?
I have four other files and i want to rotate differently. i post some photos to understand what i want to do.
any other way to do this?
Circle one
Circle two
Complete circle

Answer 1

The problem is that the rotated pixmap has a bigger bounding rectangle.
Consider the following example:
The light blue square shows the actual bounding rectangle of the rotated image, which is bigger.
Using drawPixmap(rectF, self.arch1, QRectF(self.arch1.rect())) will cause to painter to draw the pixmap in the rectangle rectF, using the new bounding rectangle as source, so it becomes "smaller".
Instead of rotating the image, you should rotate the painter. Since transformations by default use the origin point of the painter (0, 0), we need first to translate to the center of the rectangle, rotate the painter, and then retranslate back to the origin.
Note that in the following example I'm also always drawing starting from the source image, without modifying it: continuously applying a transformation will cause drawing artifacts due to aliasing, and after some rotation the quality would be very compromised.
The rotation variable is to keep track of the current rotation.
class Window(QWidget):
def __init__(self, *args, **kwargs):
# ...
self.rotation = 0
def rotate_item(self):
self.rotation = (self.rotation + 36) % 360
rectF = QRectF(0,0,556,556)
pix = QPixmap(556,556)
painter = QPainter(pix)
painter.translate(rectF.center())
painter.rotate(self.rotation)
painter.translate(-rectF.center())
painter.drawPixmap(0, 0, self.arch1)
painter.end()
self.label.setPixmap(pix)