How to refresh the view in QGIS Print Composer using Python?

Question

I am trying to automate the printing of maps based on different attribute classifications using Python in QGIS. Everything is okay except for when I open the printed image, the labels are blurry. Manually, I can fix this problem by clicking the "Refresh View" button in the print composer window, but I cannot find the right way to automatically refresh the map in the print composer based on the QGIS API. Here is printing part of this code:

def printMyMap(canvas, field, itemp):
    canvas.refresh()
    mapRenderer = canvas.mapRenderer()
    c = QgsComposition(mapRenderer)
    myFile = 'C:/Users/User1/'+itemp
    myTemplateFile = file(myFile, 'rt')
    myTemplateContent = myTemplateFile.read()
    myTemplateFile.close()
    myDocument = QDomDocument()
    myDocument.setContent(myTemplateContent)
    c.loadFromTemplate(myDocument)

    #Map
    cmaps =  c.composerMapItems()
    cmaps[0].updateCachedImage()
    cmaps[1].updateCachedImage()

    #Legend Titles
    #legend = c.getComposerItemById("3")
    #legend.setTitle(ltitle)

    #Show Composer
    #iface.actionPrintComposer().trigger()
    composerList=iface.activeComposers()
    composerView=composerList[composerList.index(max(composerList))]
    composer = composerView.composerWindow()
    composer.show()

    #Save out
    dpi = c.printResolution()
    dpmm = dpi / 25.4
    width = int(dpmm * c.paperWidth())
    height = int(dpmm * c.paperHeight())

    image = QImage(QSize(width, height), QImage.Format_ARGB32)
    image.setDotsPerMeterX(dpmm * 1000)
    image.setDotsPerMeterY(dpmm * 1000)
    image.fill(0)

    imagePainter = QPainter(image)
    sourceArea = QRectF(0, 0, c.paperWidth(), c.paperHeight())
    targetArea = QRectF(0, 0, width, height)
    c.render(imagePainter, targetArea, sourceArea)
    imagePainter.end()
    image.save("F:/Maps/"+field+".png", "png")

Answer 1

You're very close - you need to change:

sourceArea = QRectF(0, 0, c.paperWidth(), c.paperHeight())
targetArea = QRectF(0, 0, width, height)
c.render(imagePainter, targetArea, sourceArea)

to

c.renderPage( imagePainter, 0 )

As the renderPage method automatically handles a lot of output setup.