Add transparency option to images.Overlay

[gytisrepecka]

Image watermarking was introduced with v0.80.0 and can be used calling Images.Overlay function. It is nice, however, to make watermark (logo that is overlayed on top of original image) less intrusive, it makes sense to set transparency (alpha channel) value like this (bottom-right logo has Alpha value 70 out of 100):

I have implemented image watermarking using standard Go image library, so it would not be difficult to add Alpha setting to Images.Overlay. Default parameter could be 100 (overlayed image is not transparent at all), but when correct number specified, it could get transparent at specified rate.

Would this be something community would find useful to be added to image processing?

Related issues: #4595, #8057.

[bep]

I would welcome such a change.

A note to others looking at this issue: The Overlay function does support Alpha channel today, so if you overlay an image with transparency, that is preserved (which I guess is good enough for most watermarking situations -- it's not hard to edit 1 image by hand).

[gytisrepecka]

I would welcome such a change.

A note to others looking at this issue: The Overlay function does support Alpha channel today, so if you overlay an image with transparency, that is preserved (which I guess is good enough for most watermarking situations -- it's not hard to edit 1 image by hand).

Would be cool to have an ability to set a level of transparency in shortcode parameter as bright images might look better with watermark having smaller visibility value while darker images might require 90-100% of watermark visibility.

I will make a Pull Request with this modificiation 🤓 Is it better to modify Overlay filter or create a separate one?

[bep]

Is it better to modify Overlay filter or create a separate one?

Add an option. Call it opacity (which is what PhotoShop uses), 0-100%.

[jmooring]

Superseded by #11471

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