Thumbnail rules

Be aware of these thumbnail rules.

1. If catalog::ThumbType=Crop, then the (cropped) image is scaled to the smallest size possible while still covering the entire target rect. If catalog::ThumbType=Fit, then the (cropped) image is scaled to the largest size possible while still fitting the entire image into the target rect. If catalog::ThumbType=Texture, the (cropped) image is scaled to the ratio of catalog::ThumbRes to catalog::Resolution.
2. Align the scaled image with the target rect based on attribute::ThumbHorizAlign and attribute::ThumbVertAlign.
3. Crop the result to the target rect.