Y-Convert - Technical Details

I know there are many programs around who can do this job already even for free. But, if you read the above description carefully, you may have noticed I said Y-Convert is intelligent, so I must think the others are stupid in some way. OK, here's the story:

Not only while preparing my many pictures of the famous Loveparade and other events in Berlin I found that an image robot that could batch-convert and esp. downsize large DigiCam-pictures would be a useful tool to own. So I tried all I could find on the net (and there are lots of!), but with each and every I run into the same, stupid problem:
If there's an option to sharpen the output images at all, sharpening is applied using the fixed value set in the program's options - no matter what the source and the target size of the image are.

Why does this matter?
Well, say you have two images, one of 1024x768 and one of 800x600 pixels; the output for your web page should be 640x480. When you now rescale the images (no matter how good your sampling algorithm is!), pictures should be sharpened to regain best possible quality.
But: Even if the output size is the same, the downscaled 1024x768 pic can be sharpened much better (say: more!) than that of 800x600!
I can see this effect when using PicturePublisher 8, Corel's Photo-Paint 8, the demo of Paintshop Pro and even IrfanView, so this seems not to be a specific problem of the software I'm using. And, trying the demo's of the available robots that do allow sharpening (no names here, you know which ones I'm talking about!), I found that the 1024x768 picture did not have best quality while that of 800x600 did already show slight artifacts of "over-sharpening" (visual bright lines along dark edges, graininess).

My conclusion: Sharpening scaled images using a fixed value seems not to be the best idea.

Now you can guess why I call Y-Convert intelligent:
It applies an increasing amount of sharpening to pictures which are about to be downscaled, depending on the amount of scaling done to them! And I had to find out the hard way that this can not be done using a simple linear function; I literally made some hundred conversions with different scaling- and sharpening-factors to gain repeatable results with different input images.
However, sharpness is a subjective, visual impression; therefore, the strength of "Auto Enhance"ing done to your pictures can be adjusted to suit your needs or personal taste.