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https://issues.apache.org/jira/browse/CLEREZZA-716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13445954#comment-13445954
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Daniel Spicar commented on CLEREZZA-716:
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Now there can be several ImageReader services present.
An ImageReader simply provides methods to get BufferedImages from different
input sources (Files, InputStreams, URLs).
Services can implement the ImageReader interface to provide Buffered Images
using various methods and libraries.
By default there is an ImageReader service which uses javax.imageio
(ImageIO.read) to implement the functionality. This service is called
ImageIOImageReader and has a service.ranking of 0.
There is another service: ImageReaderService. This service provides a method to
dynamically obtain the ImageReader with the highest service.ranking value.
Additionally this service implements the ImageReader interface as well and
delegates the calls to the highest ranking ImageReader service. However it is
not registered in the OSGI SCR as offering the ImageReader service so one has
to bind it as ImageReaderService.
I tried to replace all instances where ImageIO.read is used by usage of
ImageReaderService.
Thus now it is possible to implement and register additional ImageReaders that
provide BufferedImages in a different way (e.g. using JAI - Java Advanced
Imaging). By setting their service ranking property to a higher value than the
default 0, they will be used over the default ImageIO service. By declaring the
property explicitly not private one can even change the service ranking via the
config admin at runtime.
> Support alternate image processing libraries for reading image data
> -------------------------------------------------------------------
>
> Key: CLEREZZA-716
> URL: https://issues.apache.org/jira/browse/CLEREZZA-716
> Project: Clerezza
> Issue Type: Improvement
> Components: platform, rdf.utils
> Affects Versions: 0.2-incubating
> Reporter: Daniel Spicar
> Assignee: Daniel Spicar
> Priority: Minor
> Time Spent: 12.5h
> Remaining Estimate: 0h
>
> Currently clerezza uses Java Image IO to read images and create
> BufferedImages. This is done in various places such as the
> ImageMetaDataGenerator and the AlternativeRepresentationGenerator. However
> the Java ImageIO implementation can fail with some JPEGs that have certain
> meta data stored that does not conform exactly to JPEG specification. In
> order to handle such cases there should be a possibility register other
> libraries or implementations that generate BufferedImages and handle these
> cases.
> I suggest to create a BufferedImageProvider OSGi service and use it in the
> meta data generators mentioned above. There should also be a default
> implementation of this service that uses Java ImageIO. Clients should then be
> able to register services that override this service and may have different
> implementations that return BufferedImages. I think it might work with the
> service-ranking property but I am not sure.
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