Integrate with forthcoming libvips v8.5.0 logging improvements

[puzrin]

When i process a lot of images, sometime something like this is printed to console:

vips warning: VipsJpeg: bad exif meta "exif-ifd3-GPSVersionID"
vips warning: icc_transform: embedded profile incompatible with image

Unexpected console texts are not acceptable - that can destroy terminal output (progress bars etc). Is it possible to suppress such things (i think that should be default behaviour)?

[lovell]

Hello, these are from libvips - set the VIPS_WARNING environment variable to suppress them, e.g. https://github.com/lovell/sharp/blob/master/package.json#L35

[puzrin]

I'm looking for long-term solution. It looks strange that additional actions should be applied to make module work right (and uncontrolled console writes is a bug for server side IMHO). May be we should report to libvips that warnings should be off by default (then anyone can enable those via env)?

[puzrin]

Reported to libvips. I hope, all will agree that writing to console from library is not a good practice.

[lovell]

Thanks Vitaly, I'll leave this open to track integration with any new libvips API when available.

[lovell]

I expect the sharp API to access libvips' log entries will probably look something like:

sharp.log.on('warning', (err) => {
  console.log(`libvips warning ${err.message}`);
});

Note that this event handler is registered against the sharp.log singleton rather than a sharp instance as there's no obvious way to tie a log entry back to a given input/pipeline.

[puzrin]

@lovell IMHO sharp.on('warning', ...) would be more simple, since sharp is already EventEmitter instance.

Anyway, those warnings looks useless. Probably it worth to disable those at all or dump to console via debug package. You can add interface later, if anyone request it, but i doubt this will ever happens.

I think, real problem is that now warnings poison console output, not "how to read those".