On Mon, Mar 28, 2011 at 9:22 AM, Ben Caradoc-Davies <[email protected]> wrote: > +1. Nice work. I am impressed. Image comparison is notoriously difficult, > and it is a good idea to recycle other tools. > > My one suggestion is to consider other tolerance options. In particular, the > integer tolerance does not look like it scales with image size. I expect you > are honouring pdiff's native options. If you double the image in each > dimension, do you have to have to quadruple your tolerance? Would a double > representing a fraction of total pixels be a bit more user-friendly? For > example, we might want to fail a test if 0.01% of pixels change, regardless > of image size. Is this good practice? Who knows. (Thinking of noise scaling > laws.)
Yeah, I wrestled with the idea in the weekend and eventually decided it would have been a dangerous one. Consider a small image, 300x100. Now think of a small percentage... 1%? 1% is 300 pixels difference, a solid black line crossing the image. Can it be ignored? Not really. The thing is, no matter how big the image is a solid blob of 100 pixes is visible to anyone. So the choice of perceptualdiff of using pixel count is a good on imho, percentages can really be deceptive. > > Would it be useful to add an ImageAssert.Options class to allow other > options to be set? This might allow either style (integer or fraction) to be > used transparently. Yeah, I could go for that. PerceptualDiff offers other three options, field of view, gamma and luminance to drive the comparison, we could expose them all: http://pdiff.sourceforge.net/ > > Well done: two static methods and already you have users asking for more > features. :-) And I did not even commit that so far! Cheers Andrea -- ------------------------------------------------------- Ing. Andrea Aime GeoSolutions S.A.S. Tech lead Via Poggio alle Viti 1187 55054 Massarosa (LU) Italy phone: +39 0584 962313 fax: +39 0584 962313 mob: +39 333 8128928 http://www.geo-solutions.it http://geo-solutions.blogspot.com/ http://www.youtube.com/user/GeoSolutionsIT http://www.linkedin.com/in/andreaaime http://twitter.com/geowolf ------------------------------------------------------- ------------------------------------------------------------------------------ Enable your software for Intel(R) Active Management Technology to meet the growing manageability and security demands of your customers. Businesses are taking advantage of Intel(R) vPro (TM) technology - will your software be a part of the solution? Download the Intel(R) Manageability Checker today! http://p.sf.net/sfu/intel-dev2devmar _______________________________________________ Geotools-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-devel
