gm convert: Unrecognized units type

Question

I try to compress PNG by GraphicsMagick(1.3.23 Q8), here is the command:

gm convert -units Undefined -type palette -define png:format=png8 src.png dest.png

and it comes with error:

gm convert: Unrecognized units type (Undefined).

"gm convert -help" shows that units type supports PixelsPerInch, PixelsPerCentimeter, or Undefined.

Acctually, I also try ImageMagick(7.0.1-6 Q8 x86_64),and the command following works fine:

convert -units Undefined -type palette -define png:format=png8 src.png dest.png

I am confused about the error.

score 1 · Accepted Answer · answered May 25 '16 at 12:27

1

Use "+units" instead of "-units Undefined" (this works with both ImageMagick and GraphicsMagick). In general, you can use "+option" to turn off most options. The documentation should be clarified.

answered May 25 '16 at 12:27

Glenn Randers-Pehrson

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Sock it to them, Glenn! :-) – Mark Setchell May 25 '16 at 13:00
Thanks, it works:) The image that compressed use with GraphicsMagick sometimes is larger than use ImageMagick, and larger than the original image. It is my command line question? – dodolzg May 26 '16 at 02:44
@dodolzg As you observed, sometimes ImageMagick and GraphicsMagick achieve different PNG compression ratios, depending upon the image content. – Glenn Randers-Pehrson May 26 '16 at 03:05

gm convert: Unrecognized units type

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