Problem with WEBP images conversion with Travis CI

[peter279k]

As title, I've found these image formats have some concerned problems.

• According to the official reference, the imagebmp provided by GD extension only supports on php-7.2+.

This package requires php-7.2 version at least and can solve this problem.

That's why I do this on this PR #3.

• According to the previous failed Travis CI build log, it looks like the php environment in Travis CI doesn't support the webp image.

I think we have to use the customized Docker image inside Travis CI if we need to test the webp image conversion.

[jenstornell]

As we talked about somewhere else, PHP 7.1+ should be required.

I don't have a solution for the webp problem, but I think it's important to keep that format, as it may be the standard image format in the future.

[peter279k]

@jenstornell, I've created the discussion about webp image support on Travis-CI community.

[peter279k]

@jenstornell, after researching a lot about building PHP with imagewebp support in Travis CI environment, I just find the "hard-core" way to resolve this.

Here are the Travis CI build log and repository:

• Travis CI log
• php-travis-gd

The Travis CI will use the phpenv to switch pre-installed PHP version for doing CI works.

To avoid this work, I use the sudo permission to install a PHP version in Travis CI environment.

[jenstornell]

I need to learn Travis CI to understand how it all works.

I can see that the last run did not get any errors, so that's a good thing. If this works without too much trouble, maybe we could use that until a better solution shows up?