Convert this png file to a pdf file or djvu file?

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http://unix.stackexchange.com – I would like to convert a png file to a pdf file or a djvu file. Following are what I have tried and all failed: I tried ImageMagick's convert convert supporting_hyperplane.png supporting_hyperplane.pdf but a large part of the image was cropped off in the pdf file. I also try to firstly include the image in a tex file and then compile it into a pdf file, but it says Cannot determine size of graphic in ./supporting_hyperplane.png So I wonder what I shall do now? Thanks and regards! (HowTos)