How to get image compression quality from IIOMetadata?

When saving a new image wit开发者_StackOverflow中文版h ImageIO generic ImageWriteParam supports explicit setting of compressionQuality parameter from range 0.0f (high compression) to 1.0f (high quality) regardless of image compression algorithm used (eg. png, jpeg, gif).

• Is there any way to read compressionQuality from an existing image?
• Is that compressionQuality write parameter just a hint to ImageWriter and is not stored anywhere in image's metadata? If that's true how image processing software (e.g. GIMP) manages to provide the following option in 'Save As' dialog?

I managed to read IIOMetadata from ImageInputStream and iterate through its metadataFormatNames to print out image metadata in different XML formats (native and standard javax_imageio_1.0, usually). Although I couldn't find any indication of image's compressionQuality in there.

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I don't think that compressionQuality is stored with image meta data, this is processing parameter only.