# PyQtImageViewer
Yet another [PyQt](https://www.riverbankcomputing.com/software/pyqt/intro) (version 4 or 5) image viewer widget. Comes prepackaged with several configurable options for display (aspect ratio, scroll bars) and mouse interaction (zoom, pan, click signals).
Displays a *QImage* or *QPixmap*. To display any other image format, you must first convert it to a *QImage* or *QPixmap*. Some useful image format conversion utilities:
* [qimage2ndarray](https://github.com/hmeine/qimage2ndarray): [NumPy](http://www.numpy.org) *ndarray* <==> *QImage*
* [ImageQt](https://github.com/python-pillow/Pillow/blob/master/PIL/ImageQt.py): [PIL](https://github.com/python-pillow/Pillow) *Image* <==> *QImage*
**Author**: Marcel Goldschen-Ohm
**Email**: <marcel.goldschen@gmail.com>
**License**: MIT
Copyright (c) 2015 Marcel Goldschen-Ohm
## INSTALL
Everything's in `QtImageViewer.py`. Just put it somewhere where your project can find it.
### Requires:
* [PyQt](https://www.riverbankcomputing.com/software/pyqt/intro) (version 4 or 5)
## A Simple Example
```python
import sys
try:
from PyQt5.QtCore import Qt, QT_VERSION_STR
from PyQt5.QtGui import QImage
from PyQt5.QtWidgets import QApplication, QFileDialog
except ImportError:
try:
from PyQt4.QtCore import Qt, QT_VERSION_STR
from PyQt4.QtGui import QImage, QApplication, QFileDialog
except ImportError:
raise ImportError("Requires PyQt5 or PyQt4.")
from QtImageViewer import QtImageViewer
# Custom slot for handling mouse clicks in our viewer.
# Just prints the (row, column) matrix index of the
# image pixel that was clicked on.
def handleLeftClick(x, y):
row = int(y)
column = int(x)
print("Pixel (row="+str(row)+", column="+str(column)+")")
if __name__ == '__main__':
# Create the QApplication.
app = QApplication(sys.argv)
# Create an image viewer widget.
viewer = QtImageViewer()
# Set viewer's aspect ratio mode.
# !!! ONLY applies to full image view.
# !!! Aspect ratio always ignored when zoomed.
# Qt.IgnoreAspectRatio: Fit to viewport.
# Qt.KeepAspectRatio: Fit in viewport using aspect ratio.
# Qt.KeepAspectRatioByExpanding: Fill viewport using aspect ratio.
viewer.aspectRatioMode = Qt.KeepAspectRatio
# Set the viewer's scroll bar behaviour.
# Qt.ScrollBarAlwaysOff: Never show scroll bar.
# Qt.ScrollBarAlwaysOn: Always show scroll bar.
# Qt.ScrollBarAsNeeded: Show scroll bar only when zoomed.
viewer.setHorizontalScrollBarPolicy(Qt.ScrollBarAsNeeded)
viewer.setVerticalScrollBarPolicy(Qt.ScrollBarAsNeeded)
# Allow zooming with right mouse button.
# Drag for zoom box, doubleclick to view full image.
viewer.canZoom = True
# Allow panning with left mouse button.
viewer.canPan = True
# Load an image to be displayed.
if QT_VERSION_STR[0] == '4':
fileName = QFileDialog.getOpenFileName(None, "Open image file...")
elif QT_VERSION_STR[0] == '5':
fileName, dummy = QFileDialog.getOpenFileName(None, "Open image file...")
image = QImage(fileName)
# Display the image in the viewer.
viewer.setImage(image)
# Handle left mouse clicks with your own custom slot
# handleLeftClick(x, y). (x, y) are image coordinates.
# For (row, col) matrix indexing, row=y and col=x.
# ImageViewerQt also provides similar signals for
# left/right mouse button press, release and doubleclick.
viewer.leftMouseButtonPressed.connect(handleLeftClick)
# Show the viewer and run the application.
viewer.show()
sys.exit(app.exec_())
```
