Vjylku

some days ago i upgraded from qgis 2.18 to 3.6.0 - not knowing that many python scripts won't run without modifications :(

i could convert all of them but not this one:

from PyQt4.QtCore import *

from PyQt4.QtGui import *

from PyQt4 import QtGui 

import processing, sys, time, psycopg2

import pprint



...

creatin layers skipped (got this running)

...



################### Create Graph #####################



mapRenderer = iface.mapCanvas().mapRenderer()



layers = [missingLayer.id(),clipLayer.id()]

mapRenderer.setLayerSet(layers)



c = QgsComposition(mapRenderer)

c.setPlotStyle(QgsComposition.Print)



c.setPaperSize(148,90)

c.setPrintResolution(300)



# add map

x, y = 0, 0

w, h = c.paperWidth(), c.paperHeight()

composerMap = QgsComposerMap(c, x,y,w,h)

c.addItem(composerMap)



#output to image

dpi = c.printResolution()

dpmm = dpi / 25.4

width = int(dpmm * c.paperWidth())

height = int(dpmm * c.paperHeight())



BackgroundColor = QColor(0,0,255)



# create output image and initialize it

image = QImage(QSize(width, height), QImage.Format_ARGB32)

image.setDotsPerMeterX(dpmm * 1000)

image.setDotsPerMeterY(dpmm * 1000)

image.fill(BackgroundColor)



header = QgsComposerLabel(c)

header.setItemPosition(40,1)

header.setBackgroundEnabled(0)

newFont = QFont("Comic Sans MS", 18)

header.setFont(newFont)

header.setText("Missing Countries Map")

header.adjustSizeToText()

c.addItem(header)



header2 = QgsComposerLabel(c)

header2.setItemPosition(50,11)

header2.setBackgroundEnabled(0)

newFont2 = QFont("Comic Sans MS", 10)

header2.setFont(newFont2)

header2.setText("TS="+ts)

header2.adjustSizeToText()

c.addItem(header2)



footer = QgsComposerLabel(c)

footer.setItemPosition(124,87.5)

footer.setBackgroundEnabled(0)

newFont3 = QFont("Times Roman", 4)

footer.setFont(newFont3)

footer.setText(time.ctime())

footer.adjustSizeToText()

c.addItem(footer)



legend = QgsComposerLegend(c)

legend.model().setLayerSet(mapRenderer.layerSet())

legend.setItemPosition(5,65)

legend.setFrameEnabled(1)

newFont = QFont("Comic Sans MS", 6)

legend.setStyleFont(QgsComposerLegendStyle.Title, newFont)

legend.setStyleFont(QgsComposerLegendStyle.Subgroup, newFont)

legend.setStyleFont(QgsComposerLegendStyle.SymbolLabel, newFont)

legend.setStyleMargin(QgsComposerLegendStyle.Title,2)

legend.setTitle("Legend")

legend.setSymbolHeight(2)

legend.adjustBoxSize()

c.addItem(legend)



# render the composition

imagePainter = QPainter(image)

imagePainter.setRenderHint(QPainter.Antialiasing)

sourceArea = QRectF(0, 0, c.paperWidth(), c.paperHeight())

targetArea = QRectF(0, 0, width, height)

c.render(imagePainter, targetArea, sourceArea)

imagePainter.end()

imageFile = "missing_boundaries"+ts+".png"

print "saving to "+imageFile

image.save(imageFile)

yes, i do know the QqsComposer has gone but i can't find any documentation or example for QGIS3 plotting. Exept the API description of course.
:(

any hints how to start will help. don't need the whole script converted by you, only the first few lines should be enought.