IOS中UIImage的数据量压缩有两种方式，一种是图片尺寸不变，降低图片分辨率，代码方法为：

//1.0为压缩系数，介于0~1之间。压缩系数越小，会大大降低图片清晰度

NSData *data = UIImageJPEGRepresentation(originalImage, 1.0);

另一种是按比例减小图片的尺寸，从而减小图片内存

按比例缩小图片尺寸的代码

-(UIImage )scaleImage:(UIImage )image toScale:(float)scaleSize
{
UIGraphicsBeginImageContext(CGSizeMake(image.size.widthscaleSize,image.size.heightscaleSize));
[image drawInRect:CGRectMake(0, 0, image.size.width * scaleSize, image.size.height *scaleSize)];
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage;
}