PyQt4 - python-djvulibre Segmentation Fault

Question

While I was trying to write a small program to preview DjVu files I encountered a peculiar problem. This is a small function that renders a page of a DjVu document into QImage class of PyQt4.

import djvu.decode as DjVu
from PyQt4.QtCore import QImage
from PyQt4.QtGui import QPixmap, QApplication, QLabel

def djvu2pixmap( filename, width, height ) :
    doc = DjVu.Context().new_document( DjVu.FileURI( filename ) )
    doc.decoding_job.wait()
    pg = doc.pages[ 0 ]
    pg.decode( wait = True )
    data = pg.thumbnail.render( ( width, height ), DjVu.PixelFormatRgbMask( 0xff0000, 0xff00, 0xff, bpp = 32 ) )
    image = QIamge( data[ 1 ], data[ 0 ][ 0 ], data[ 0 ][ 1 ], QImage.Format_RGB32 )
    image.save( "/tmp/image.png" )
    return QPixmap.fromImage( image )

if __name__ == '__main__' :

    import sys

    app = QApplication( sys.argv )

    lbl = QLabel()
    lbl.setPixmap( djvu2pixmap( "trial.djvu" ), 200, 300 )
    lbl.show()
    lbl.resize( lbl.pixmap().size() )

    exit( app.exec_() )

Say now I set the image width and height to ( 300, 500 ) the program crashes out with SegmentationFault. I also realized that there is no problem with the image. It does get saved properly. I just cannot display it. Not only that, but I can open the saved image and display it without any problem. Im curious as to why this happens.

Answer 1

It turns out that the problem was with the the python-djvu package. A later version of the python-djvu package resolved the issue.

Answer 2

It's possible your QPixmap is being deleted immediately after you call lbl.setPixmap. Try this instead:

pixmap = djvu2pixmap( "trial.djvu" )
lbl.setPixmap( pixmap, 200, 300 )