vips_foreign_find_load missing

[kleisauke]

In order to pass the correct options before the Image::newFromFile operation, the vips_foreign_find_load will come in handy to determine the image format.

Example:
The page property works only for PDFs, TIFFs, and multi-size ICOs (or any other image that has more than one page). But doesn't work for a JPEG (it will fail with the error: Message: jpegload: no property named 'page'). In order to pass the page property to the correct loader we can check first with vips_foreign_find_load if the operation permits a page property.

[jcupitt]

I agree, I think it'd be a useful improvement. We should add the one for buffers as well, I guess.

In the meantime, you could just open the file and look at the vips-loader property. It records the name of the load operation that was used:

$ vipsheader -f vips-loader k2.jpg 
jpegload

So open once, get loader name, open a second time with whatever arguments you want.

[jcupitt]

OK, in git master. Thanks!

[jcupitt]

git master php-vips has a wrapper as well, with a fallback to the property method:

https://github.com/jcupitt/php-vips/blob/master/src/Image.php#L716

and a version for buffers.

[kleisauke]

Nice! Travis is currently failing because the newest version of php-vips-ext isn't on PECL yet, I think we can ignore it for now.

[jcupitt]

OK, fixed travis. It turns out you can't catch undefined functions :(