DeepZoom: Does DeepZoom Composer compress your images?

I read a complaint from a reader about the lost of image quality in DeepZoom last night, which puzzled me as I never encountered this problem before. So, I decided to fire up DeepZoom Composer to test it.

So here is the original picture submitted by my reader....


And this is the result achieved by the reader...


And it is very obvious that both images are different. Judging from the file size, I guess the second image is cropped from the screenshoot.

From my understanding, DeepZoom composer converts images into JPG format then resizes and slices the images. There should be no compression going on.

So, I took the original image, DeepZoom it then copy the output to my Silverlight project. And the result is shown in the screenshot below....



The original image is on the left hand side. In the middle, you can see my testing DeepZoom application running in Firefox. On the right had side is the DeepZoom-ed image from the reader.

In my testing project, the output image from DeepZoom Composer looks exactly the same as displayed in MultiScaleImage control of Silverlight, so I leave it out from the screenshot capture. Also, I tested it on IE7, and the result is still the same as in Firefox.

If we compare carefully, the image shown in Firefox has darker colours. Beyond this, I can't spot any obvious difference in quality. I guess the darker colour is caused by conversion from PNG format to JPG format (I have tested it with other JPG images as the source images, and the output looks exactly the same as the source images).

In conclusion, DeepZoom Composer does not change your images although some differences may be caused by conversion into JPG format.

So, now the interesting question is - how the reader got that kind of output?? I am puzzled....is it caused by IE6 or other browsers? Or some properties are changed for the MultiScaleImage control??

By the way, you can download my test project from here. The DeepZoom project is a VB project. The mouse and keyboard support codings are not written by me but taken from MSDN Code Gallery.