Breaking change in 1.19.0

[garrows]

Hi,
Love the module but your latest change seems to have broken things for me.

I'm getting the error for several files.
improper image header-' @ error/png.c/ReadPNGImage/3921`

Downgrading to 1.18.1 fixed the problem for me.

[rwky]

When reporting bugs please include the version of graphicsmagick/imagemagick you're using (gm -version/convert -version) as well as the version of this module and copies of any images you're having problems with.

[garrows]

Apologies. I'm usually more useful but I was in a rush (and sadly still am)

ImageMagick 6.9.1-10 Q16 x86_64
GraphicsMagick 1.3.21 2015-02-28 Q8

Tried on node v4.0.0 and v0.10.40

I'll try to get you some sample code later on.

[rwky]

Can you see if this is fixed in 1.20.0?

[garrows]

That has fixed it for both 0.10 and 4.0. Thank you!

[adurrive]

Hello @garrows,

I've looked at most of the problems caused by 1.19.0 and I've made a new pull request. Your issue however would likely fail again.

Currently, the module does not provide the image format of buffers and streams to gm, as you may expect when providing a filename. If you used something like gm(buffer, 'image.png'), the second argument is essentially ignored and gm has no idea the buffer is a PNG. In most cases, this is fine since gm is able to find the correct format automatically. But in some others, it simply makes buffers and streams unusable.

1.19.0 attempted to fix this and restore the expected behaviour. This means that an incorrect filename, which until now had no impact at all, would fail. The correct way to use the automatic format inference, however, remains: if you do not provide a filename, using something like gm(buffer), gm will analyse the file signature as it does today.

It would be great to look further at the problematic files you used and how you used them to rule out other unforeseen issues. Would you still have them?

[garrows]

That's unfortunate. If you do have to make the breaking change make sure its on a major version change though.

The module I was having trouble with is https://github.com/garrows/IMMP which has a few tests which I think were failing with 1.19.0. I hope this helps.

[adurrive]

Thanks I think I've spotted the issue and it's a miss on my part. I'll fix it and let @rwky decide what to do with the pull request.