RFR: 8277572: ImageStorage should correctly handle MIME types for images encoded in data URIs [v5]

[Michael Strauß]

> `com.sun.javafx.iio.ImageStorage` currently ignores the MIME image subtype specified for images encoded in data URIs. This should be improved as follows:
> 
> 1. If the specified image subtype is not supported, an exception will be thrown.
> 2. If the specified image subtype is supported, but the data contained in the URI is of a different (but also supported) image format, the image will be loaded and a warning will be logged. For example, if the MIME type is "image/jpeg", but the image data is PNG, the following warning will be generated:
> 
> 
> Image format 'PNG' does not match MIME type 'image/jpeg' in URI 'data:image/jpeg;base64,iVBORw0KGgoAAA...AAAElFTkSuQmCC'
> 
> 
> Also, the javadoc of `javafx.scene.image.Image` incorrectly states:
> 
>     94    * If a URL uses the "data" scheme, the data must be base64-encoded
>     95    * and the MIME type must either be empty or a subtype of the
>     96    * {@code image} type.
> 
> However, omitting the MIME type of a data URI is specified to imply "text/plain" (RFC 2397, section 2). Since the `com.sun.javafx.util.DataURI` class is implemented according to this specification, trying to load an image without MIME type correctly fails with an `ImageStorageException`: "Unexpected MIME type: text".
> 
> The solution is to fix the documentation:
> 
>       94    * If a URL uses the "data" scheme, the data must be base64-encoded
>     - 95    * and the MIME type must either be empty or a subtype of the
>     - 96    * {@code image} type.
>     + 95    * and the MIME type must be a subtype of the {@code image} type.
>     + 96    * The MIME type must match the image format of the data contained in
>     + 97    * the URL. In case of a mismatch between MIME type and image format,
>     + 98    * the image will be loaded if the image format can be determined by
>     + 99    * JavaFX, and a warning will be logged.

Michael Strauß has updated the pull request incrementally with one additional commit since the last revision:

  revert code change

-------------

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/676/files
  - new: https://git.openjdk.java.net/jfx/pull/676/files/4cb5678a..35a41e06

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=676&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=676&range=03-04

  Stats: 3 lines in 1 file changed: 0 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/jfx/pull/676.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/676/head:pull/676

PR: https://git.openjdk.java.net/jfx/pull/676