Get pixel coordinates on-click in QGIS

qgis_pixel_coordinates.py

"""
Get pixel coordinates (not geographic coordinates) of a location in a raster. 

Run the script to activate the tool. 
Click a location to see row, column printed to Python console.
Click any other tool to deactivate.

Original source: https://gis.stackexchange.com/a/261538/67365

Modified slightly from the original for compatibility with Python 3 + QGIS 3 - Hannover
"""

from qgis.gui import QgsMapTool
from PyQt5.QtCore import Qt, QPoint
from math import floor

# references to QGIS objects 
canvas = iface.mapCanvas() 
layer = iface.activeLayer() 
data_provider = layer.dataProvider()

# properties to map mouse position to row/col index of the raster in memory 
extent = data_provider.extent() 
width = data_provider.xSize() if data_provider.capabilities() & data_provider.Size else 1000 
height = data_provider.ySize() if data_provider.capabilities() & data_provider.Size else 1000 
xres = extent.width() / width 
yres = extent.height() / height

class ClickTool(QgsMapTool): 
    def __init__(self, canvas):
        QgsMapTool.__init__(self, canvas)
        self.canvas = canvas 

    def canvasPressEvent(self, event):
        if event.button() == Qt.LeftButton: 
            x = event.pos().x()
            y = event.pos().y()

            # clicked position on screen to map coordinates
            point = self.canvas.getCoordinateTransform().toMapCoordinates(x, y)

            if extent.xMinimum() <= point.x() <= extent.xMaximum() and \
                extent.yMinimum() <= point.y() <= extent.yMaximum():
                col = int(floor((point.x() - extent.xMinimum()) / xres))
                row = int(floor((extent.yMaximum() - point.y()) / yres))

                print(f"{row}, {col}")

tool = ClickTool(iface.mapCanvas())
iface.mapCanvas().setMapTool(tool)