$ for f in *; do convert $fg png/$f.png; done
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.                                                                             
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.                                                                             
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.                                                                             
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.                                                                             
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.                                                                             
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.                                                                             
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.                                                                             
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.
convert: unable to open image `':  @ error/blob.c/OpenBlob/2484.                                                                             
convert: missing an image filename `png/aaa.tif.png' @ error/convert.c/ConvertImageCommand/2919.

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