silx.gui: Updated OpenGL text rendering to use Qt when possible

src/silx/gui/_glutils/font.py

@@ -1,6 +1,6 @@
 # /*##########################################################################
 #
-# Copyright (c) 2016-2023 European Synchrotron Radiation Facility
+# Copyright (c) 2016-2024 European Synchrotron Radiation Facility
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -21,19 +21,129 @@
 # THE SOFTWARE.
 #
 # ###########################################################################*/
+from __future__ import annotations
 """Text rasterisation feature leveraging Qt font and text layout support."""
 
 __authors__ = ["T. Vincent"]
 __license__ = "MIT"
 __date__ = "13/10/2016"
 
 
+import logging
+import numpy
+
 from .. import qt
+from ..utils.image import convertQImageToArray
+from ..utils.matplotlib import rasterMathText
+
 
-# Expose rasterMathText as part of this module
-from ..utils.matplotlib import rasterMathText as rasterText  # noqa
+_logger = logging.getLogger(__name__)
 
 
 def getDefaultFontFamily() -> str:
     """Returns the default font family of the application"""
     return qt.QApplication.instance().font().family()
+
+
+def rasterTextQt(
+    text: str,
+    font: qt.QFont,
+    dotsPerInch: float = 96.0,
+) -> tuple[numpy.ndarray, float]:
+    """Raster text using Qt.
+
+    It supports multiple lines.
+
+    :param text: The text to raster
+    :param font: Font to use
+    :param dotsPerInch: The DPI resolution of the created image
+    :return: Corresponding image in gray scale and baseline offset from top
+    """
+    if not text:
+        _logger.info("Trying to raster empty text, replaced by white space")
+        text = " "  # Replace empty text by white space to produce an image
+
+    dotsPerMeter = int(dotsPerInch * 100 / 2.54)
+
+    # get text size
+    image = qt.QImage(1, 1, qt.QImage.Format_Grayscale8)
+    image.setDotsPerMeterX(dotsPerMeter)
+    image.setDotsPerMeterY(dotsPerMeter)
+
+    painter = qt.QPainter()
+    painter.begin(image)
+    painter.setPen(qt.Qt.white)
+    painter.setFont(font)
+    bounds = painter.boundingRect(
+        qt.QRect(0, 0, 4096, 4096), qt.Qt.TextExpandTabs, text
+    )
+    painter.end()
+
+    metrics = qt.QFontMetrics(font)
+    offset = metrics.ascent() / 72.0 * dotsPerInch
+
+    # This does not provide the correct text bbox on macOS
+    # size = metrics.size(qt.Qt.TextExpandTabs, text)
+    # bounds = metrics.boundingRect(
+    #     qt.QRect(0, 0, size.width(), size.height()),
+    #     qt.Qt.TextExpandTabs,
+    #     text)
+
+    # Add extra border
+    width = bounds.width() + 2
+    # align line size to 32 bits to ease conversion to numpy array
+    width = 4 * ((width + 3) // 4)
+    image = qt.QImage(
+        int(width),
+        int(bounds.height() + 2),
+        qt.QImage.Format_Grayscale8,
+    )
+    image.setDotsPerMeterX(dotsPerMeter)
+    image.setDotsPerMeterY(dotsPerMeter)
+    image.fill(0)
+
+    # Raster text
+    painter = qt.QPainter()
+    painter.begin(image)
+    painter.setPen(qt.Qt.white)
+    painter.setFont(font)
+    painter.drawText(bounds, qt.Qt.TextExpandTabs, text)
+    painter.end()
+
+    array = convertQImageToArray(image)
+
+    # Remove leading and trailing empty columns/rows but one on each side
+    filled_rows = numpy.nonzero(numpy.sum(array, axis=1))[0]
+    filled_columns = numpy.nonzero(numpy.sum(array, axis=0))[0]
+
+    if len(filled_rows) == 0 or len(filled_columns) == 0:
+        return array, offset
+    return (
+        numpy.ascontiguousarray(
+            array[
+                0 : filled_rows[-1] + 2,
+                max(0, filled_columns[0] - 1) : filled_columns[-1] + 2,
+            ]
+        ),
+        offset,
+    )
+
+
+def rasterText(
+    text: str,
+    font: qt.QFont,
+    dotsPerInch: float = 96.0,
+) -> tuple[numpy.ndarray, float]:
+    """Raster text using Qt or matplotlib if there may be math syntax.
+
+    It supports multiple lines.
+
+    :param text: The text to raster
+    :param font: Font name or QFont to use
+    :param dotsPerInch: Created image resolution
+    :return: Corresponding image in gray scale and baseline offset from top
+    """
+
+    if text.count("$") >= 2:
+        return rasterMathText(text, font, dotsPerInch)
+    return rasterTextQt(text, font, dotsPerInch)