v5

doc/constrain/constrain.xq

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+(:~ 
+ :examples of constrain use
+:)
+import module namespace t="expkg-zone58:image.thumbnailator";
+declare variable $file-base:=file:parent(static-base-uri());
+
+declare variable $src:=file:resolve-path("A17057.jpg",$file-base);
+declare function local:wi($data as xs:base64Binary,$filename as xs:string)
+{
+  file:write-binary(file:resolve-path($filename,$file-base),$data)
+};
+declare function local:constrain($aspect as xs:boolean,$fit as xs:boolean,$exif as xs:boolean)
+{
+<thumbnail>
+  <size width="60" height="200"/>  
+  <constrain aspect="{$aspect}" fit="{$fit}" exif="{$exif}"/>
+</thumbnail>
+};
+let $s:=function($b){if($b) then ".+" else ".-"}
+let $img:= fetch:binary($src)
+let $ft:=(false(),true())
+for $fit in $ft,$aspect in $ft,$exif in $ft
+let $file:=("out.",
+           $s($aspect) , "aspect",
+           $s($fit), "fit",        
+           $s($exif), "exif",
+            ".jpg")=>string-join("")
+let $task:=local:constrain($aspect,$fit,$exif)
+return t:task($img,$task) => local:wi($file)

doc/readme.md

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+# expkg-zone58:image.thumbnailator
+
+The schema is [task.xsd](../src/main/content/task.xsd)
+
+## thumbnail node
+
+![root](thumbnail-schema.png "thumbnail node")
+
+Either `size` or `scale` must be specified. Everything else is optional
+
+`output` can be used to change the output image format.
+
+```
+<output format="gif"/>
+```
+
+## Filters
+
+![filter definition](filters-schema.png "Available filters")
+
+## Exif
+Image handling is effected by the presence of the 
+[exif-orientation](http://www.daveperrett.com/articles/2012/07/28/exif-orientation-handling-is-a-ghetto/) tag.
+In particular:
+* `size` and `fit` are changed
+* the `flip` filter is ignored
+
+To prevent this set constrain @exif=false
+
+```
+<constrain exif="false"/>
+```