Add a failing test for vips::VError exception

[salzhrani]

There is a discrepancy between the raw buffer size that is emitted and expected. it is my understanding that a raw image buffer size should be the product of width * height * channels but it seems that there is a difference in rounding of the image dimensions. in the specific case in this test the buffer length should be 840 * 473 * 3 = 1191960 but instead 1189440 is emitted which seems to be the product of 840 * 472 * 3

[lovell]

Hi Samy, there was a recent problem highlighted by #387 (comment) where it was possible to get incorrect values for info.width and info.height passed to the callback. I think this might be related, in that info.size is correct but info.height is off-by-one due to a rounding that takes place after the height is calculated.

If so, the fix here is probably to ensure the width and height are based on the actual dimensions of the final output image rather than an intermediate calculation.

[salzhrani]

It might be best if vips is the single source of image metadata if possible

[lovell]

I agree, thanks Samy. Setting width and height on the baton approximately here should fix this. Happy to accept a PR for this if you're willing and able :)

[salzhrani]

Thanks for the opportunity ... I also took the opportunity to add a try/catch.

[coveralls]

Coverage remained the same at 98.832% when pulling cff1602 on salzhrani:failed-test into f214269 on lovell:master.

[coveralls]

Coverage remained the same at 98.832% when pulling 053ba09 on salzhrani:failed-test into f214269 on lovell:master.

[lovell]

This looks great, thanks for the work on this.

What's the origin of the flower.jpeg test image? Are you able to add a source URL (you'll see these against most of the other test fixtures), assuming it's been made available for us to use under a suitable licence?

[salzhrani]

The image can be found here. Not sure about the licence. I can replace it with a another with the same dimensions and more explicit license if you want.

[salzhrani]

Added a blank image with the correct dimensions.

[coveralls]

Coverage remained the same at 98.832% when pulling d9b6993 on salzhrani:failed-test into f214269 on lovell:master.

[lovell]

Fantastic work, than you very much for this Samy!

[salzhrani]

@lovell If appropriate please cut us a 0.14.1 release. It seems all issues on the milestone are covered.

[lovell]

@salzhrani v0.14.1 now available via npm, thanks for your additions!