How to gather coordinates from a .tif image and insert them to PyQt code

[john_hobbyist]

Hello, I use this code here: https://github.com/kklmn/OrthoView/blob/master/OrthoView.py As I see this part here (line 109):

class MyToolBar(mpl_qt.NavigationToolbar2QT):
    def set_message(self, s):
        try:
            parent = self.parent()
        except TypeError:  # self.parent is not callable
            parent = self.parent

        try:
            sstr = s.split()
#            print(sstr, len(sstr))
            while len(sstr) > 5:  # when 'zoom rect' is present
                del sstr[0]
#            print(sstr)
            x, y = float(sstr[0][2:]), float(sstr[1][2:])
            if parent.canTransform():
                xC, yC = parent.beamPosRectified
                if not parent.buttonStraightRect.isChecked():
                    xP, yP = parent.transformPoint((x, y))
                    x0, y0 = (xP-xC)/parent.zoom, (yP-yC)/parent.zoom
                    s = u'image: x={0:.1f} px, y={1:.1f} px\nplate: '\
                        'x={2:.2f} mm, y={3:.2f} mm'.format(x, y, x0, y0)
                else:
                    x0, y0 = (x-xC)/parent.zoom, (y-yC)/parent.zoom
                    s = 'plate: x={0:.2f} mm, y={1:.2f} mm'.format(x0, y0)
            else:
                s = u'image: x={0:.1f}, y={1:.1f}'.format(x, y)
        except Exception as e:
            pass
#            print(e)

        if self.coordinates:
            self.locLabel.setText(s)

is involved with the x,y coordinates. I need to do the following: to get the coordinates from the .tif image I load and put them inside the code, so that instead x,y coordinates to show the real coordinates of the .tif. I am thinking of using the gdal package but I do not know which lines I should change on the above code and how to achieve this transformation, can you help me? Thank you...

[john_hobbyist]

I am trying to reproduce this interesting code from here: https://stackoverflow.com/questions/50191648/gis-geotiff-gdal-python-how-to-get-coordinates-from-pixel by giving random test values on x, y:

# open the dataset and get the geo transform matrix
ds = gdal.Open('final.tif') 
xoffset, px_w, rot1, yoffset, px_h, rot2 = ds.GetGeoTransform()

x = 100000
y = 100000

# supposing x and y are your pixel coordinate this 
# is how to get the coordinate in space.
posX = px_w * x + rot1 * y + xoffset
posY = rot2 * x + px_h * y + yoffset

# shift to the center of the pixel
posX += px_w / 2.0
posY += px_h / 2.0

but I get this error:

free(): invalid pointer
Aborted (core dumped)

Any idea, how to proceed?

[mrjj]

@john_hobbyist
Hi
Do you have a TIF called final.tif and in a location where it actually finds it?

else i guess
ds = gdal.Open('final.tif')
will result in a invalid ds and
doing
rot2 = ds.GetGeoTransform()
might crash it.

Purely guessing. sadly i dont know gdal.

[john_hobbyist]

@mrjj: instead of

ds = gdal.Open('final.tif')

I have the full path of the .tif file

ds = gdal.Open('/home/john/Desktop/UAV_image.tif')

The path is correct, in other code it works just fine

[mrjj]

@john_hobbyist
Hi
Ok, so its not that.

so it doesn't say at which line, the error comes?

[john_hobbyist]

@mrjj It only prints this, nothing else:

free(): invalid pointer
Aborted (core dumped)

I won't stuck on this searching if there is a better solution to my question on the initial post...

[john_hobbyist]

Can I run gdalinfo inside the python code (not on terminal) and get the data I need of the coordinates of the .tif's corners in order to use them on x,y (I don't know how!!) ?

[Christian Ehrlicher]

Please ask in a forum specialized to gdal and image processing. I don't see how this is related to Qt in any way.