TextItem在pyqtgraph中的缩放

Question

我在pyqtgraph中texttitems的字体缩放有问题，就像你可以从下面的代码中看到的，当我在主图中放大/缩小时，texttems的字体保持不变，而我试图使它以与qgraphicsrectem相同的方式(速率)缩放。我试着看看所有的论坛，我知道，但我还没有找到一个答案，所以我真的希望有人有一个解决方案。

import sys
import pyqtgraph as pg
from PyQt6.QtWidgets import QApplication, QGraphicsRectItem
from pyqtgraph.Qt import QtCore
app = QApplication(sys.argv)
view = pg.GraphicsView()
l = pg.GraphicsLayout()
view.setCentralItem(l)
view.show()
view.resize(800, 600)
p0 = l.addPlot(0, 0)
p0.showGrid(x=True, y=True, alpha=1.0)
# have no x-axis tickmark below the upper plot (coordinate 0,0)
# without these lines, there will be separate coordinate systems with a gap inbetween
ay0 = p0.getAxis('left')      # get handle to y-axis 0
ay0.setStyle(showValues=False)  # this will remove the tick labels and reduces gap b/w plots almost to zero
# there will be a double line separating the plot rows
# ay02 = p0.getAxis('right')
# ay02.setStyle(showValues=False)
p0.hideAxis('right')
ax02 = p0.getAxis('top')
ax02.setStyle(showValues=False)
p1 = l.addPlot(0, 1)

# p1.showGrid(x=True, y=True, alpha=1.0)
p1.setYLink(p0)
l.layout.setSpacing(0.5)
l.setContentsMargins(0., 0., 0., 0.)
p1.setFixedWidth(300)
# p1.setFixedHeight(h-451)
p1.setMouseEnabled(x=False)
# ay1 = p1.getAxis('left')
# ay1.setStyle(showValues=False)
ax12 = p1.getAxis('top')
ax12.setStyle(showValues=False)
# ax1 = p1.getAxis('bottom')
# ax1.setStyle(showValues=False)
p1.showAxis('right')
p1.hideAxis('left')
p1.setXRange(0, 6, padding=0)   # Then add others like 1 pip
# p1.getAxis('bottom').setTextPen('black')
board = ['123456',
'abcdef',
'ghilmn']

def draw_board(board2):
for j, row in enumerate(board2):
for i, cell in enumerate(row):
rect_w = 1
rect_h = 1
r = QGraphicsRectItem(i, -j+2, rect_w, rect_h)
r.setPen(pg.mkPen((0, 0, 0, 100)))
r.setBrush(pg.mkBrush((50, 50, 200)))
p1.addItem(r)
t_up = pg.TextItem(cell, (255, 255, 255), anchor=(0, 0))
t_up.setPos(i, -j+1+2)
p1.addItem(t_up)

draw_board(board)
if __name__ == '__main__':
if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
QApplication.instance().exec()

Answer 1

文本项的缩放是相当困难的，因为您需要考虑基本比例的恒定长宽比，以及与字体相对于原点的定位和绘制方式相关的问题。

假设显示的文本总是是单个字符，并且使用的字符是标准的ASCII字母和数字，唯一的可能性是循环遍历所有可能的字符，并为每个字符创建适当对齐的路径。

那么，对于每个字符:

• 构造一个QPainterPath;
• 将字母添加到路径中;
• 获取该路径宽度和其他路径的max();
• 获取边界矩形的最小Y和最大bottom;
• 基于所有上面计算的其他值转换路径(在单独的循环中);

然后，你必须为字母设置一个参考大小(使用上面的最大宽度和字体度量的高度)，并获得该大小的宽高比。

最后一部分是在qgraphicsrectem子类的paint()函数中实现的，该函数需要获得项目的正确几何形状(如果对父项目应用任何转换，该项目将不知道它)，并根据当前矩形大小获得参考尺寸的最大矩形。

class NumberRectItem(QGraphicsRectItem):
textSize = None
textPaths = {}
textPath = None
def __init__(self, x, y, width, height, letter=''):
super().__init__(x, y, width, height)
if letter:
if not self.textPaths:
self._buildTextPaths()
self.textPath = self.textPaths[letter]
def _buildTextPaths(self):
from string import ascii_letters, digits
font = QApplication.font()
fm = QFontMetricsF(font)
maxWidth = 0
minY = 1000
maxY = 0
for l in ascii_letters + digits:
path = QPainterPath()
path.addText(0, 0, font, l)
br = path.boundingRect()
maxWidth = max(maxWidth, br.width())
minY = min(minY, br.y())
maxY = max(maxY, br.bottom())
self.textPaths[l] = path
self.__class__.textSize = QSizeF(maxWidth, fm.height())
self.__class__.textRatio = self.textSize.height() / self.textSize.width()
middle = minY + (maxY - minY) / 2
for path in self.textPaths.values():
path.translate(
-path.boundingRect().center().x(), 
-middle)
def paint(self, qp, opt, widget=None):
super().paint(qp, opt, widget)
if not self.textPath:
return
qp.save()
qp.resetTransform()
view = widget.parent()
sceneRect = self.mapToScene(self.rect())
viewRect = view.mapFromScene(sceneRect).boundingRect()
rectSize = QSizeF(viewRect.size())
newSize = self.textSize.scaled(rectSize, Qt.KeepAspectRatio)
if newSize.width() == rectSize.width():
# width is the maximum
ratio = newSize.width() / self.textSize.width()
else:
ratio = newSize.height() / self.textSize.height()
transform = QTransform().scale(ratio, ratio)
path = transform.map(self.textPath)
qp.setRenderHint(qp.Antialiasing)
qp.setPen(Qt.NoPen)
qp.setBrush(Qt.white)
qp.drawPath(path.translated(viewRect.center()))
qp.restore()

def draw_board(board2):
for j, row in enumerate(board2):
for i, cell in enumerate(row):
rect_w = 1
rect_h = 1
r = NumberRectItem(i, -j+2, rect_w, rect_h, letter=cell)
r.setPen(pg.mkPen((150, 0, 0, 255)))
r.setBrush(pg.mkBrush((50, 50, 200, 128)))
p1.addItem(r)

^{注意:对于PyQt6，您需要使用完整的enum名称:Qt.GlobalColor.white等。}