Steps to Reproduce

1. import keikai-636.xlsx

Current Result

java.lang.NullPointerException
io.keikai.model.SPicture$Format.valueOfFileExtension(SPicture.java:45)
io.keikai.importer.XlsxImporter.importPicture(XlsxImporter.java:1106)
io.keikai.importer.XlsxImporter.importDrawings(XlsxImporter.java:1028)
io.keikai.importer.XlsxImporter.imports(XlsxImporter.java:326)
io.keikai.range.impl.imexp.ExcelImportAdapter.imports(ExcelImportAdapter.java:48)
io.keikai.range.impl.imexp.AbstractImporter.imports(AbstractImporter.java:57)
io.keikai.ui.Spreadsheet.getSBook(Spreadsheet.java:725)
io.keikai.ui.Spreadsheet.getSelectedSSheet(Spreadsheet.java:905)
io.keikai.ui.Spreadsheet.doInvalidate(Spreadsheet.java:2779)
io.keikai.ui.Spreadsheet.invalidate(Spreadsheet.java:2632)
io.keikai.ui.Spreadsheet.setSrc(Spreadsheet.java:972)

Expected Result

• no exception
• print a warning message: ignore an external image at [SHEET!CELL_ADDRESS]
• still render the file content

Debug Information

• the file contains an external image. Sine keikai cannot render that image, it's better to ignore it and render the content without an exception.
• Check keikai-636.xlsx/xl/drawings/_rels/drawing1.xml.rels, you will find:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
    <Relationship Id="rId3"
        Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/image"
        Target="../media/image2.png" />
    <Relationship Id="rId2"
        Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/image"
        Target="cid:[email protected]" TargetMode="External" />
    <Relationship Id="rId1"
        Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/image"
        Target="../media/image1.jpeg" />
    <Relationship Id="rId4"
        Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/image"
        Target="../media/image3.png" />
</Relationships>

Workaround

• remove the external image or turn it into an internal image