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• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
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• Tests for the changes are included.

What is the current behavior?

Right now, cli cannot generate assets the alpha of which is disabled.
Output:

ns resources generate icons ./icon.png

Generating icons ...
image.colorType is not a function

This behaviour broke during 8.9 update and update of Jimp dependency.

What is the new behavior?

Cli will be able to generate assets the alpha of which is disabled (rgba: true).