feat: add retainExif option to retain Exif

[zcf0508]

Summary

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of the default theme, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)

You have tested in the following browsers: (Providing a detailed version will be better.)

• Chrome
• Firefox
• Safari
• Edge
• IE

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated
• Related tests have been updated

To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

By default, the Exif information will be lost in the compressed image. If you want to keep the Exif information of the original image you can set the retainExif option to true

[zcf0508]

Reference 使用CANVAS压缩JPG图片丢失EXIF信息问题 .

[fengyuanchen]

Is it necessary to add this feature? This is a question that requires careful consideration.

In fact, you can read Exif metadata on the browser side and upload it to the server side as a parameter along with the compressed image.

[zcf0508]

@fengyuanchen
Thanks for the reply. In my case, I use this lib to build a browser-side image compress website, I hope that the users can choose whether or not to retain the Exif when they save the compressed image.

[patilanz]

Hey this feature will be very helpful. It can save a lot of time.

[lorenzomorandini]

@fengyuanchen I would like to ask for this feature to be merged too.
Having the image and the metadata divided adds a few challenges, first of all keeping them linked and consistent.

[RokuDagy]

Indeed, it would be useful to at least have the option to chose since it doesn't impact the code to much

[Robert-Lebedeu]

I was looking for this feature and I would love to see this merged.
If the purpose of this library is to compress images client-side, I don't see why you shouldn't have an option to keep the metadata.

[lorenzomorandini]

News on this?

[rgbskills]

Any updates?

[mjau-mjau]

Just a related comment. It would be amazing if this option (or similar option) could also retain IPTC data (caption, copyright, keywords etc). I believe the goal is to be able to compress images, while keeping ALL image meta data, as this is largely beneficial for image galleries etc when uploading and compressing images.