Try this for calculating a new and fitting image;
Adjust newRect
to the rect of your cell.
// scale and center the image
CGSize sourceImageSize = [artworkImage size];
// The rectangle of the new image
CGRect newRect;
newRect = CGRectMake(0, 0, 40, 33);
// Figure out a scaling ratio to make sure we maintain the same aspect ratio
float ratio = MAX(newRect.size.width / sourceImageSize.width, newRect.size.height / sourceImageSize.height);
UIGraphicsBeginImageContextWithOptions(newRect.size, NO, 1.0);
// Center the image in the thumbnail rectangle
CGRect projectRect;
projectRect.size.width = ratio * sourceImageSize.width;
projectRect.size.height = ratio * sourceImageSize.height;
projectRect.origin.x = (newRect.size.width - projectRect.size.width) / 2.0;
projectRect.origin.y = (newRect.size.height - projectRect.size.height) / 2.0;
[sourceImage drawInRect:projectRect];
UIImage *sizedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
cell.imageView.image = sizedImage;