The idea of Regard is to have a tool that would automatically detect many kinds of regressions during the development of Batik project. It uses Java 2D API's to produce the image difference to visually faciliate the developer to distinguish regressions with improvement during the code changes.

Before doing any regression check, there'll be an initilization, during which three directories will be established: regard-dir/svg : The SVG test files will be put under this directory regard-dir/ref : The reference image files will be generated from the SVG files under regard-dir/svg, before the code changes are made regard-dir/new : The new image files will be generated from the SVG files under regard-dir/svg, after the code changes are made, but before the code changes will be checked in

After initilization, the users can generate the reference images from the SVG test files before they make any changes to the Batik code; then after they made changes as they want, and before they want the changes to be checked in to the Batik code base, the user should generate new images from the same SVG test files and compare the new generated images with the reference images. The result will be reported in an HTML file under the regard-dir. If there's any regression, there'll be links in the report file directing to the difference image, in which the original image, the new image and the difference between them is recorded.

General command: java -classpath ... org.apache.batik.apps.regard.Main [-help|-init|-reset|-ref|-new|-diff]

-help Display the usage message

-init Initialize the workspace, generate a working directory of Regard and three sub-dir under it: svg, ref and new

-ref Generate the reference image files from the SVG test files

-new Generate the new image files from the same SVG test files

-diff Generate the differnce report in an HTML file with links to the difference image files, if any, that are stored under a sub-dir named diff