How to extract the image in JPXDecode

[thaihaquang]

Dear authors,
I am trying your tool to extract images from PDF using the below code

for i in range(len(doc)):
    for img in doc.getPageImageList(i):
        print("Processing ", i)
        xref = img[0]
        print (img)
        pix = fitz.Pixmap(doc, xref)
        if pix.n < 5:       # this is GRAY or RGB
            pix.writePNG("./out/p%s-%s.png" % (i, xref))
        else:               # CMYK: convert to RGB first
            pix1 = fitz.Pixmap(fitz.csRGB, pix)
            pix1.writePNG("./out/p%s-%s.png" % (i, xref))
            pix1 = None
        pix = None

All files are extracted OK, except a PDF file.

Each image in that PDF are saved to 2 strange images
I found that the decode filter of the image is "JPXDecode"
Below is the information I got from doc.getPageImageList(i)
[(85, 0, 1262, 1769, 8, 'DeviceRGB', '', 'Bg', 'JPXDecode'), (87, 86, 631, 885, 8, 'DeviceRGB', '', 'CL', 'JPXDecode')]

Could you help me to explain the reason and guide me on how to fix this issue?
Thank you very much.