How do I specify the PPM format?

[Nakilon]

I see that by default the ppm format is P6. How do I change it?
.write_to_file "temp.ppm[format=P5]"

ppmsave: no property named `format' (Vips::Error)

.write_to_file "temp.ppm", format: "P5"

unable to call VipsForeignSavePpmFile: unknown option format (Vips::Error)

[jcupitt]

Hi @Nakilon,

It's done from the file extension, so .pfm saves as float, for example. There's also pgm, pbm, .pgm. and .ppm.

8.14 has a new feature where saving as .pnm will automatically use the best format for your data.

https://github.com/libvips/libvips/blob/gh-pages-8.14/_posts/2022-12-22-What's-new-in-8.14.md#other

[jcupitt]

Oh, format should work too. I see:

$ vips copy k2.jpg x.ppm[format=pfm]
$ more x.ppm
PF
#vips2ppm - 2022-12-24T11:31:30.717226Z
1450 2048
-1
...

Maybe you have an old version of libvips? format was added in 8.13.

[Nakilon]

Oh, yes, it's vips-8.11.3-Wed Aug 11 09:29:27 UTC 2021