PyQTGraph ImageExporter bug related to image size

Question

I am using pyqtgraph to produce plots in a PyQT window. I want to export PNG image of the graphs.

I have this error when I try to export my plots:

ImageExporter.py", line 70, in export bg = np.empty((self.params['width'], self.params['height'], 4), >dtype=np.ubyte) TypeError: 'float' object cannot be interpreted as an integer

I noticed that the self.params['width'] and self.params['height'] are floats. But np.empty can not create an erray using float sizes.

Even if i set the width and height manually using :

exporter.parameters()['width'] = self.raw_DataPlot.width()
exporter.parameters()['height'] = self.raw_DataPlot.height()

The results are floats.

I noticed that If I change the line 70 of ImageExporter.py to :

bg = np.empty((int(self.params['width']), int(self.params['height']), 4),dtype=np.ubyte)

The export works fine.

Is it possible to address this issue and update the library? Or is there a workaround that doesn't push me to change the pyqtgraph library itself.

Thanks

Answer 1

To solve this problem, I created a new ImageExporter that I integrated to my project. I called this exporter PQG_ImageExporter so that we don't get confused.

I signaled this problem on github. I hope they fix it soon. When the problem will be solved, I can get back to the classic ImageExporter :

from pyqtgraph.exporters import Exporter
from pyqtgraph.parametertree import Parameter
from pyqtgraph.Qt import QtGui, QtCore, QtSvg, USE_PYSIDE
from pyqtgraph import functions as fn
import numpy as np
import pyqtgraph as pg

__all__ = ['PQG_ImageExporter']


class PQG_ImageExporter(Exporter):
    Name = "Image File (PNG, TIF, JPG, ...)"
    allowCopy = True

    def __init__(self, item):
        Exporter.__init__(self, item)
        tr = self.getTargetRect()
        if isinstance(item, QtGui.QGraphicsItem):
            scene = item.scene()
        else:
            scene = item
        # scene.views()[0].backgroundBrush()
        bgbrush = pg.mkBrush('w')
        bg = bgbrush.color()
        if bgbrush.style() == QtCore.Qt.NoBrush:
            bg.setAlpha(0)

        self.params = Parameter(name='params', type='group', children=[
            {'name': 'width', 'type': 'int',
                'value': tr.width(), 'limits': (0, None)},
            {'name': 'height', 'type': 'int',
                'value': tr.height(), 'limits': (0, None)},
            {'name': 'antialias', 'type': 'bool', 'value': True},
            {'name': 'background', 'type': 'color', 'value': bg},
        ])
        self.params.param('width').sigValueChanged.connect(self.widthChanged)
        self.params.param('height').sigValueChanged.connect(self.heightChanged)

    def widthChanged(self):
        sr = self.getSourceRect()
        ar = float(sr.height()) / sr.width()
        self.params.param('height').setValue(
            self.params['width'] * ar, blockSignal=self.heightChanged)

    def heightChanged(self):
        sr = self.getSourceRect()
        ar = float(sr.width()) / sr.height()
        self.params.param('width').setValue(
            self.params['height'] * ar, blockSignal=self.widthChanged)

    def parameters(self):
        return self.params

    def export(self, fileName=None, toBytes=False, copy=False):
        if fileName is None and not toBytes and not copy:
            if USE_PYSIDE:
                filter = ["*."+str(f)
                          for f in QtGui.QImageWriter.supportedImageFormats()]
            else:
                filter = ["*."+bytes(f).decode('utf-8')
                          for f in QtGui.QImageWriter.supportedImageFormats()]
            preferred = ['*.png', '*.tif', '*.jpg']
            for p in preferred[::-1]:
                if p in filter:
                    filter.remove(p)
                    filter.insert(0, p)
            self.fileSaveDialog(filter=filter)
            return

        targetRect = QtCore.QRect(
            0, 0, self.params['width'], self.params['height'])
        sourceRect = self.getSourceRect()

        #self.png = QtGui.QImage(targetRect.size(), QtGui.QImage.Format_ARGB32)
        # self.png.fill(pyqtgraph.mkColor(self.params['background']))
        w, h = self.params['width'], self.params['height']
        if w == 0 or h == 0:
            raise Exception(
                "Cannot export image with size=0 (requested export size is %dx%d)" % (w, h))
        bg = np.empty((int(self.params['width']), int(
            self.params['height']), 4), dtype=np.ubyte)
        color = self.params['background']
        bg[:, :, 0] = color.blue()
        bg[:, :, 1] = color.green()
        bg[:, :, 2] = color.red()
        bg[:, :, 3] = color.alpha()
        self.png = fn.makeQImage(bg, alpha=True)

        # set resolution of image:
        origTargetRect = self.getTargetRect()
        resolutionScale = targetRect.width() / origTargetRect.width()
        #self.png.setDotsPerMeterX(self.png.dotsPerMeterX() * resolutionScale)
        #self.png.setDotsPerMeterY(self.png.dotsPerMeterY() * resolutionScale)

        painter = QtGui.QPainter(self.png)
        #dtr = painter.deviceTransform()
        try:
            self.setExportMode(True, {
                               'antialias': self.params['antialias'], 'background': self.params['background'], 'painter': painter, 'resolutionScale': resolutionScale})
            painter.setRenderHint(
                QtGui.QPainter.Antialiasing, self.params['antialias'])
            self.getScene().render(painter, QtCore.QRectF(
                targetRect), QtCore.QRectF(sourceRect))
        finally:
            self.setExportMode(False)
        painter.end()

        if copy:
            QtGui.QApplication.clipboard().setImage(self.png)
        elif toBytes:
            return self.png
        else:
            self.png.save(fileName)


PQG_ImageExporter.register()