ImageMagick convert: "unable to extend cache"

[^rooker]

[PROBLEM]
I wanted to deinterlace a video image frame, using ImageMagick's "convert" tool. In order to get every 2nd line out of the image, I've called it as follows:

Code: Select all

convert 1-B.tga -sample 100%50% 1-B.png

...and was returned with a strange error message:

convert: unable to extend cache `xxx.tga': Invalid argument.
convert: No IDATs written into file `xxx.png'.

[SOLUTION]
Actually, the error message was right: "Invalid argument" - but I was confused by the "unable to extend cache blabla no IDATs written to file xxx" stuff.
I've had a typo in my "-sample" argument. It was:

Code: Select all

100%50%

but was missing an "x" in between:

Code: Select all

100%x50%