ImageStream implementation

[weierophinney]

Q	A
Documentation	no
Bugfix	yes
BC Break	future
New Feature	yes
RFC	no
QA	no

Description

Per discussion in #57, this patch does the following:

• Introduces the ImageStream class as an extension of Stream that only works with GdImage resources.
• Updates Stream to emit an E_USER_DEPRECATED error when used with a GdImage resource, pointing users to the new ImageStream implementation.
• Updates StreamFactory::createStreamFromResource() to detect GdImage resources, and to create and return an ImageStream when it does.

The plan will be for 3.0.0 to remove support for GdImage from Stream.

[boesing]

Summing up Slack discussion:

Currently, neither PHP 7.4 nor 8.0 with both resource or GdImage are properly functioning as both GdImage and the resource which are passed do not contain the image type. So should the image created as an PNG or a JPEG? Lacking this information, using stream_get_contents on the gdimage resource will result in:

Warning: stream_get_contents(): supplied resource is not a valid stream resource

For PHP 8.0 and GdImage, that error will slightly change to Warning: Uncaught TypeError: stream_get_contents(): Argument #1 ($stream) must be of type resource, GdImage given.

So the whole image feature is non-existent and therefore never worked. Won't be even a BC break by removing this feature tho.

[weierophinney]

Based on the Slack conversation and the feedback here, I'm going to close this patch, and then open a new one against 3.0.x to drop support for GD images in Stream.