outstanding issues with image module

[duncdrum]

What is the problem

• Currently the xquery functions exposed by the image module are not tested.
• Support for imageIO varies between different Java engines, in particular openJDK has some nasty bugs, which are unlikely to get fixed any time soon. s.b.
• Transformation functions inadvertently strip alpha channels in both jpg and png and convert them to black (or whatever default background color is defined elsewhere).
• Crop and scale use heightxwidth in their function signature for dimensions, this is against the widely adopted standard which is widthxheight

What did you expect

• unit tests for the various functions
• working with JPEG images either results in (for non RGB color profiles)

02 Nov 2018 17:38:42,773 [qtp443401609-49] ERROR (CropFunction.java [eval]:154) - Unable to read image data! 

or when running in openJDK (with supported jpeg)

<error type="java:java.lang.NoClassDefFoundError" message="Could not initialize class com.sun.imageio.plugins.jpeg.JPEGImageReader"/>

this means we can't process JPEG within our docker images

• The colors in the following two images to look identical

original	transformed

• image dimensions to follow common practice of walking down the hall to get to the elevator (Width x Height)

Describe how to reproduce or add a test

• xqsuite test PR is wip
• see Image module can’t initialize class javax.imageio.ImageIO #2242
• run:

xquery version "3.1";

import module namespace image="http://exist-db.org/xquery/image";

declare variable $testCol := '/db/GH/2242';
declare variable $png := 'https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png';
let $store := xmldb:store(
        $testCol, 
        'image.png',
        hc:send-request(<hc:request href="{$png}" method="get"/>)[2]
let $somePNG := util:binary-doc($testCol || '/image.png')

return
  xmldb:store('/db/GH/2242', 'scaled.png', image:scale($somePNG, (),'image/png'))

• see L118-9

Context information

Please always add the following information

• eXist-db 4.4.0
• Java version (e.g. Java8u181 Java8u191) openJDK / oracleJDK
• Operating system ( Linux, MacOs)
• 64 bit
• How is eXist-db installed? ( DMG, clone from GitHub, docker)
• Any custom changes in e.g. conf.xml. n.a.

[dizzzz]

@duncdrum regarding the "Could not initialize class com.sun.imageio.plugins.jpeg.JPEGImageReader" ... this makes sense ; do you have a full trace? is this without the JAI module installed?

[duncdrum]

see #805