ImageCropper, SaveAs with BitmapFileFormat.Png seems like not PNG file but bitmap

Describe the bug

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• Is this bug a regression in the toolkit? If so, what toolkit version did you last see it work:

I have several PNG files (Android snapshots, 600x1024 pixels, with size about 400 kB. After cropping to about 300x350 pixels, and using imageCropper.SaveAs(.., BitmapFileFormat.Png) file size is almost same, and should be much smaller. When I open such cropped file in Microsoft Imaging Suite Editor, and save as new PNG file, file size is four..five times smaller.

When I use ImageMagick to simply open/save (no edits): magick convert Screenshot_20200413-223246.png magScreenshot_20200413-223246.png file size is reduced from 452 KiB to 118 KiB.

Seems like imageCropper.SaveAs saves pixels in PNG but as bitmap, without any compression (should use deflate, as stated in PNG format description).

Steps to Reproduce

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2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior

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Screenshots

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Environment

NuGet Package(s): 
6.0.0
Package Version(s): 

Windows 10 Build Number:
- [ ] Fall Creators Update (16299)
- [ ] April 2018 Update (17134)
- [ ] October 2018 Update (17763)
- [ ] May 2019 Update (18362)
- [X] second 2019 Update (18363)
- [ ] Insider Build (build number: )

App min and target version:
- [ ] Fall Creators Update (16299)
- [X] April 2018 Update (17134)
- [ ] October 2018 Update (17763)
- [ ] May 2019 Update (18362)
- [ ] Insider Build (xxxxx)

Device form factor:
- [X] Desktop
- [ ] Xbox
- [ ] Surface Hub
- [ ] IoT

Visual Studio 
- [ ] 2017 (version: )
- [X] 2019 (version: 16.4.2 ) 
- [ ] 2019 Preview (version: )

Additional context

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