image rotation

I've got a question about canvas rotation. Everytime I I try to totate the canvas arbitrarily the qualtiy goes way down, but if I rotate it 90 or 180 degrees it doesn't change. Most of my images need to be rotated 45 degrees. Is there any way to keep the image quality from going down or a way to fix it?

Thanks,
John

If you have a typical image, with square pixels, then naturally rotating the canvas 90 or 180 or 270 degrees will not affect it's quality. Imagine you have a grid of square pixels. You can freely rotate those pixels but after you choose a rotation angle then Photoshop must take the pixels of your image and fit them back into that square grid. At 90, 180, and 270 the pixels you rotated will still be in alignment with that grid and fit back in perfectly. And any other amount of rotation then your pixels won't fit neatly back into the grid. They will be at an angle and PS will have to quantize the pixels, which usually produces a blurring effect.