#886 Support capturing PNG as intermediate format

[He Xintong]

On the settings I saw the following notice:

Select the file format used for saving photos. This affects "standard" (not RAW) photos. Only JPEG supports saving Exif metadata. Note that PNG format is not truly lossless, instead it is converted from a JPEG at 100% quality.

But on the PNG specification I saw there is already have a section described the eXIf trunk to store the EXIF metadata, making it possible to store such data into PNG format, so I suggest add an feature to capture the PNG photo as intermediate format before saving JPG and WebP photo, and, what's more, it's possible to save a lossless WebP photo.

[He Xintong]

See also: https://en.wikipedia.org/wiki/Portable_Network_Graphics#Ancillary_chunks

[Anonymous]

This is awesome! heck, any newer formats can be added in a breeze! I request you mark sir, please implement this.

[He Xintong]

See this discussion here:
https://github.com/beatbrot/ScreenshotAssistant/issues/55
Also see the following comment:
https://github.com/beatbrot/ScreenshotAssistant/commit/3d8ce0dc0e2580a6ba55d3379654b67ad79d9112

[He Xintong]

The official PNG specification also added HDR support, making it possible to interchange HDR information with other image formats.

https://www.w3.org/TR/png-3/

[Mark]

The next version will support Exif interface for PNG and WebP. Note it's not possible to capture directly as PNG - the JPEG data comes direct from the camera driver (although possibly this could be done by requesting data in YUV_420_888 format). Thanks for the info on PNG and HDR. I think UltraHDR is only currently supported via JPEG and HEIC formats, so there's a gap here (if I use YUV_420_888 format to get a lossless result, there wouldn't be any HDR info to add to the PNG result).

[He Xintong]

Note it's not possible to capture directly as PNG - the JPEG data comes direct from the camera driver (although possibly this could be done by requesting data in YUV_420_888 format).

if I use YUV_420_888 format to get a lossless result, there wouldn't be any HDR info to add to the PNG result).

To my eyes, such circumstances should be documented in Open Camera Help.

I think UltraHDR is only currently supported via JPEG and HEIC formats, so there's a gap here

If this is right, and could be reproduced in several ways, I think this should be also informed in Open Camera Help.