Copy only the matplotlib image and make background transparent

Author: pshriwise

openmc_plotter/plotgui.py

@@ -1,3 +1,4 @@
+import io
 from functools import partial
 
 from PySide6 import QtCore, QtGui
@@ -182,22 +183,60 @@ def saveImage(self, filename):
 
     def copyImageToClipboard(self):
         """Copy the current canvas image to the clipboard."""
-        self.draw()
-        width, height = self.get_width_height()
-        if width <= 0 or height <= 0:
+        image = self._export_plot_image()
+        if image is None:
             return False
 
-        image = QtGui.QImage(self.buffer_rgba(),
-                             width,
-                             height,
-                             QtGui.QImage.Format_RGBA8888).copy()
-        pixmap = QtGui.QPixmap.fromImage(image)
-        if pixmap.isNull():
+        clipboard = QtGui.QGuiApplication.clipboard()
+        if clipboard is None:
             return False
 
-        QtGui.QGuiApplication.clipboard().setPixmap(pixmap)
+        clipboard.setImage(image)
         return True
 
+    def _export_plot_image(self):
+        self.draw()
+        width, height = self.get_width_height()
+        if width <= 0 or height <= 0:
+            return None
+
+        buffer = io.BytesIO()
+        self.figure.savefig(buffer,
+                            format='png',
+                            transparent=True)
+        image = QtGui.QImage.fromData(buffer.getvalue(), 'PNG')
+        if image.isNull():
+            return None
+
+        crop_rect = self._visible_canvas_rect(image.width(), image.height())
+        if crop_rect.isEmpty():
+            return None
+
+        return image.copy(crop_rect)
+
+    def _visible_canvas_rect(self, image_width, image_height):
+        if self.width() <= 0 or self.height() <= 0:
+            return QtCore.QRect()
+
+        if self.parent is None or not hasattr(self.parent, 'viewport'):
+            return QtCore.QRect(0, 0, image_width, image_height)
+
+        viewport = self.parent.viewport()
+        visible_width = min(viewport.width(), self.width())
+        visible_height = min(viewport.height(), self.height())
+        x_offset = self.parent.horizontalScrollBar().value()
+        y_offset = self.parent.verticalScrollBar().value()
+
+        scale_x = image_width / self.width()
+        scale_y = image_height / self.height()
+
+        return QtCore.QRect(round(x_offset * scale_x),
+                            round(y_offset * scale_y),
+                            round(visible_width * scale_x),
+                            round(visible_height * scale_y)).intersected(
+                                QtCore.QRect(0, 0, image_width, image_height)
+                            )
+
     def getDataIndices(self, event):
         cv = self.model.currentView
 

tests/setup_test/test.py

@@ -58,19 +58,21 @@ def test_batch_image(tmpdir, qtbot):
 
     mw.close()
 
-def test_copy_image_to_clipboard(tmpdir, monkeypatch):
+def test_copy_image_to_clipboard(tmpdir, monkeypatch, qtbot):
     orig = tmpdir.chdir()
     QtWidgets.QApplication.instance() or QtWidgets.QApplication([])
     mw = MainWindow(model_path=orig)
     _openmcReload(model_path=orig)
     mw.loadGui()
+    qtbot.addWidget(mw)
+    mw.show()
 
     class FakeClipboard:
         def __init__(self):
-            self.pixmap = None
+            self.image = None
 
-        def setPixmap(self, pixmap):
-            self.pixmap = pixmap
+        def setImage(self, image):
+            self.image = image
 
     fake_clipboard = FakeClipboard()
     monkeypatch.setattr(QtGui.QGuiApplication,
@@ -79,11 +81,32 @@ def setPixmap(self, pixmap):
 
     try:
         assert mw.waitForPlotIdle(60000)
+        mw.model.currentView.domainVisible = False
+        mw.plotIm.updatePixmap()
         assert mw.copyImageToClipboard()
     finally:
         orig.chdir()
 
-    assert fake_clipboard.pixmap is not None
-    assert not fake_clipboard.pixmap.isNull()
+    assert fake_clipboard.image is not None
+    assert not fake_clipboard.image.isNull()
+    assert fake_clipboard.image.hasAlphaChannel()
+
+    canvas_width, canvas_height = mw.plotIm.get_width_height()
+    expected_width = round(
+        min(mw.frame.viewport().width(), mw.plotIm.width())
+        * canvas_width
+        / mw.plotIm.width()
+    )
+    expected_height = round(
+        min(mw.frame.viewport().height(), mw.plotIm.height())
+        * canvas_height
+        / mw.plotIm.height()
+    )
+    assert fake_clipboard.image.width() == pytest.approx(expected_width, abs=1)
+    assert fake_clipboard.image.height() == pytest.approx(expected_height, abs=1)
+
+    center = fake_clipboard.image.pixelColor(fake_clipboard.image.width() // 2,
+                                             fake_clipboard.image.height() // 2)
+    assert center.alpha() == 0
 
     mw.close()

tests/test_plotgui_clipboard.py

@@ -0,0 +1,80 @@
+from types import SimpleNamespace
+
+import numpy as np
+import pytest
+from PySide6 import QtGui, QtWidgets
+
+from openmc_plotter.plotgui import PlotImage
+
+
+class FakeClipboard:
+
+    def __init__(self):
+        self.image = None
+
+    def setImage(self, image):
+        self.image = image
+
+
+@pytest.fixture
+def qapp():
+    return QtWidgets.QApplication.instance() or QtWidgets.QApplication([])
+
+
+def test_copy_image_to_clipboard_crops_to_plot_and_preserves_alpha(
+    qapp, monkeypatch
+):
+    scroll = QtWidgets.QScrollArea()
+    scroll.resize(220, 160)
+    main_window = SimpleNamespace(
+        logicalDpiX=lambda: 100,
+        zoom=100,
+        coord_label=SimpleNamespace(show=lambda: None, hide=lambda: None),
+        statusBar=lambda: SimpleNamespace(showMessage=lambda *args, **kwargs: None),
+    )
+    plot = PlotImage(model=None, parent=scroll, main_window=main_window)
+    scroll.setWidget(plot)
+    plot.resize(400, 300)
+    plot.figure.clear()
+    plot.ax = plot.figure.subplots()
+    plot.ax.imshow(np.zeros((10, 10, 4)))
+    scroll.show()
+    qapp.processEvents()
+    scroll.horizontalScrollBar().setValue(40)
+    scroll.verticalScrollBar().setValue(30)
+    qapp.processEvents()
+
+    fake_clipboard = FakeClipboard()
+    monkeypatch.setattr(
+        QtGui.QGuiApplication,
+        "clipboard",
+        staticmethod(lambda: fake_clipboard),
+    )
+
+    try:
+        assert plot.copyImageToClipboard()
+    finally:
+        plot.close()
+        scroll.close()
+
+    assert fake_clipboard.image is not None
+    assert not fake_clipboard.image.isNull()
+    assert fake_clipboard.image.hasAlphaChannel()
+
+    canvas_width, canvas_height = plot.get_width_height()
+    expected_width = round(
+        min(scroll.viewport().width(), plot.width()) * canvas_width / plot.width()
+    )
+    expected_height = round(
+        min(scroll.viewport().height(), plot.height()) * canvas_height / plot.height()
+    )
+    assert fake_clipboard.image.width() == pytest.approx(expected_width, abs=1)
+    assert fake_clipboard.image.height() == pytest.approx(expected_height, abs=1)
+    assert fake_clipboard.image.width() < canvas_width
+    assert fake_clipboard.image.height() < canvas_height
+
+    center = fake_clipboard.image.pixelColor(
+        fake_clipboard.image.width() // 2,
+        fake_clipboard.image.height() // 2,
+    )
+    assert center.alpha() == 0