Fixes black background for png images in wysiwyg editors

[eduard13]

Description

This PR fixes the black background for png images, which are uploaded in wysiwyg editors. This issue appears only for GD2 image processing library.

Fixed Issues (if relevant)

1. Transparent background becomes black for thumbnails of PNG into Wysiwyg editor... #14248: Transparent background becomes black for thumbnails of PNG into Wysiwyg editor

Manual testing scenarios

1. Upload a png image from any wysiwyg editor
2. The background while previewing of this image should be transparent.
   

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @eduard13. Thank you for your contribution
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[rogyar]

It looks like we should perform a check that $this->_imageHandler is not bool|null before passing it to $this->_fillBackgroundColor. That's the exact reason why we have unit tests failing here (it's a sort of unit-integration test :) )

[eduard13]

Thank you a lot @rogyar for the suggestion.

[osrecio]

@eduard13 Can you check the errors in Travis?

[eduard13]

@osrecio looks like this issue is caused by declaring strict types.

Do you think is it ok, if we set 1 in order to pass an int value?
Or is better to remove strict_types declaration? Looks like because of the strict type, instead of int value, receives a bool one.
Or maybe you have some other suggestions here?

https://github.com/eduard13/magento2/blob/48607aa5dcb308a27994f35aaf330e631d9a0c8b/lib/internal/Magento/Framework/Image/Adapter/Gd2.php#L184-L185

Thank you.

[sidolov]

I think we don't need constant fir true value in this class, just assign true to property when it needed

[eduard13]

Updated it, thanks.

[magento-engcom-team]

Hi @osrecio, thank you for the review.
ENGCOM-2855 has been created to process this Pull Request

[magento-engcom-team]

Hi @eduard13. Thank you for your contribution.
We will aim to release these changes as part of 2.2.7.
Please check the release notes for final confirmation.

Please, consider to port this solution to 2.3 release line.
You may use Porting tool to port commits automatically.