Le 18/11/2012 19:03, peyrol nous fit lire :
> I generated thousands of still frames to turn into a video. Most were generated
> with POVray under Debian Linux, but a few hundred were done with POVray for
> Windows. The format is png. I notice the Windows png files are uniformly 2.6 MB
> whereas the Linux png frames are in the range of 1.2 to 1.6MB. I can open the
> Windows frames with Gimp under Linux, and then save them under Gimp, which will
> reduce their size to the same as the Linux frames, and ffmpeg will then accept
> them. But when I try to run ffmpeg, I get an error when it reaches the Windows
> frames that have not been converted.
> 
> Is there some command or some app such as a Ruby script which will convert all
> my Windows frames at once, so that I don't have to convert each one manually and
> I don't have to generate them over again? Thanks.
> 
> 
I would call shenanigan on the png-fixed-size of Windows.
(which version of povray was it ? was -FN used ?)

(that does not smell like a png; Gimp is very leniant and probably
ignore the suffix, loading the BMP file)
With Imagemagick (install the package), run "identify" on one such file.
I would bet for some BMP.
(other check : BMP & PNG have a header with printable text (well, they
use magic values, which are printable). Use "od -c -N6 ..."

BMP starts with BM
PNG starts with PNG after the first byte

In the same package, use the "convert" utility.
(in a "for" loop, or with "find|xargs")

convert input.bmp output.png

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