digiKam from trunk : Light Table preview : fix tile side effect with high zoom level. This is a first approach how to solv ethis problem. It's not optimum but work fine.

What the problem exactly ? Well it's simple : we scaling a part of full image to render a preview unsing a tile matrix. The part of full image is scaled with take a care of image data outside the region. With a high zoom level the scale algorithm cannot compute properlly the border of the tile and a side effect appear.