Select feature one by one and save it as image

Question

I have used following code for selecting the features and save it as image.

layer = self.iface.activeLayer();
layer.setSelectedFeatures([])
count =layer.featureCount()
lstChalta = []
lstFeatures = processing.features(layer)
for elem in lstFeatures:
   geom = elem.geometry()
   attr = elem.attributes()
   layer.setSelectedFeatures([elem.id()])
   self.iface.mapCanvas().zoomToSelected( layer )
   box = layer.boundingBoxOfSelected()
   self.iface.mapCanvas().setExtent(box)
   self.iface.mapCanvas().refresh()
   self.iface.mapCanvas().refresh()
   cno= str(attr[layer.fieldNameIndex('cno')])
   path = 'D:\Test'+ str(cno) + '.png'
   self.iface.mapCanvas().saveAsImage(path)
   #QMessageBox.information(None, "DEBUG:", str(test))

Whenever I run the script, it is selecting only the last feature. However, if I uncomment message box line it is working fine and selecting each and every feature one by one. In addition to that it is saving the image properly.

I want to work the script without showing message.

Answer 1

I don't know if exists a better method for this question but, I found out this procedure:

How to programmatically close a QMessagebox without clicking ok or X?

where it was programmatically implemented a custom QMessageBox for automatically closing after a certain time. I tried out other methods (involving time python library) with your code but it was necessary a delay equivalent to a QMessagebox for a successfully result.

I slightly modified your code (for adapting to my system) and the proposal in the above link to use a QMessageBox without OK button.

The next code:

class CustomMessageBox(QMessageBox):

    def __init__(self, *__args):
        QMessageBox.__init__(self)
        self.timeout = 0
        self.autoclose = False
        self.currentTime = 0

    def showEvent(self, QShowEvent):
        self.currentTime = 0
        if self.autoclose:
            self.startTimer(1000)

    def timerEvent(self, *args, **kwargs):
        self.currentTime += 1
        if self.currentTime >= self.timeout:
            self.done(0)

    @staticmethod
    def showWithTimeout(timeoutSeconds, 
                        message, 
                        title, 
                        icon = QMessageBox.Information, 
                        buttons = QMessageBox.NoButton):

        w = CustomMessageBox()
        w.autoclose = True
        w.timeout = timeoutSeconds
        w.setText(message)
        w.setWindowTitle(title)
        w.setIcon(icon)
        w.setStandardButtons(buttons)
        w.exec_()

import processing
from PyQt4.QtGui import QMessageBox

layer = iface.activeLayer();
layer.setSelectedFeatures([])
count =layer.featureCount()
lstChalta = []

lstFeatures = processing.features(layer)

for elem in lstFeatures:
    geom = elem.geometry()
    attr = elem.attributes()
    layer.setSelectedFeatures([elem.id()])
    iface.mapCanvas().zoomToSelected( layer )
    box = layer.boundingBoxOfSelected()
    iface.mapCanvas().setExtent(box)
    iface.mapCanvas().refresh()
    cno= str(attr[layer.fieldNameIndex('cno')])
    path = '/home/zeito/Desktop/folder/Test'+ str(cno) + '.png'

    CustomMessageBox.showWithTimeout(.5, 
                                     'feature: ' + cno, 
                                     "Information", 
                                     icon = QMessageBox.Information)

    iface.mapCanvas().saveAsImage(path)

it was running with a vector layer where I created your 'cno' field; as it can be observed at the next image:

I took a screenshot during the automatic execution of my code (see next image for feature 3).

After running the code, the target folder had the png images as I expected.