converting bmp to grayscale png

[manit]

hi,
Here is my problem :-
$ convert -set colorspace Gray ./66/SIRE-66_6_2_HT4.bmp 66_SIRE-66_6_2_HT4.png
convert: length and filesize do not match `./66/SIRE-66_6_2_HT4.bmp' @ warning/bmp.c/ReadBMPImage/831.
$ file ./66/SIRE-66_6_2_HT4.bmp
./66/SIRE-66_6_2_HT4.bmp: PC bitmap, Windows 3.x format, 712 x 540 x 8
Input BMP File is at https://ufile.io/d1p9y

Thanks.

[snibgo]

The metadata in your BMP says the image takes zero bytes in the file. This is clearly wrong, and IM warns you about this. But it is just a warning, and the result should be okay.

[magick]

We inspected the image. It claims a file size of 1078 bytes whereas its actually 385558 and results in a warning exception.

[manit]

snibgo ,
you are right .
I saw error but command still works .

magick,
Can you tell how you found 1078 claim ?

Thanks.