将图片缩放（质量和比例变化）

- (UIImage *)resizeImage:(UIImage *)image

withQuality:(CGInterpolationQuality)quality

rate:(CGFloat)rate

{

UIImage *resized =
nil;

CGFloat width = image.size.width *
rate;

CGFloat height = image.size.height
* rate;

UIGraphicsBeginImageContext(CGSizeMake(width, height));

CGContextRef context =
UIGraphicsGetCurrentContext();

CGContextSetInterpolationQuality(context, quality);

[image
drawInRect:CGRectMake(0,
0, width, height)];

resized =
UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return resized;

}