How to input correct coordinates depending on various CRS with Python in QGIS

Question

I used a script from the PyQGISDeveloperCookbook and another StackExchange post to render an image from a specific coordinate. The problem I have is that I am unsure how to input the correct coordinates for a custom CRS. The CRS I am using in my project is ETRS89 / GK25FIN, And the coordinate I want to render is 25500381,6677153. When I attempt to render, I only output garbage similar to the result Leolo got in the previously mentioned post.

I have tried using a smaller number but the odds of me brute forcing the correct location is practically zero. Being a noob I am unsure what the given CRS actually means, and what coordinates it is supposed to use. I have tried using this site to translate the coordinates with no luck.

Here is the my slightly modified script from the previous post:

from PyQt4.QtGui import QImage, QPainter
from PyQt4.QtCore import QSize
import os

# radius for image in meters
radius = 512
# center point 
p = [25499771,6677153] # <- I don't know what to write here in this CRS
# bounding box
bbox = QgsRectangle(p[0]-radius, p[1]-radius, p[0]+radius, p[1]+radius)
# image
img = QImage(QSize(200,200), QImage.Format_ARGB32_Premultiplied)
## create painter
painter = QPainter()
painter.begin(img)
render = QgsMapRenderer()
## set layer set
layers = QgsMapLayerRegistry.instance().mapLayers()
lst = layers.keys()
render.setLayerSet(lst)

# Set destination CRS to match the CRS of the first layer
render.setDestinationCrs(layers.values()[0].crs())
# Enable OTF reprojection
render.setProjectionsEnabled(True)

## set extent
render.setExtent(bbox)
## set output size
render.setOutputSize(img.size(), img.logicalDpiX())
## do the rendering
render.render(painter)
painter.end()
## save image
img.save("K:\\QgisOutput\\TestHeight.png", "png")

Answer 1

Your code works for me in the Python console, with the first layer in GK25FIN, and the second an Openstreetmap background:

Note that the image takes the CRS of the first layer in the table of content, and there should be something to be seen in the map within 512 meters around the point.

Answer 2

The solution is to re-import the needed layers and make sure no layers are missing.

In my specific case the problem arose with the use of layers that weren't linked to their sources anymore. I created the project and used the script on two different computers, where in the latter case I had missing sources which probably messed up the data in some way. The coordinates visible in the tab from the mouse cursor location "should" always match to the ones written in the console or a script, unless something went wrong like in my case.

I hope someone finds this useful if they encounter the same issue.