iOS app存储图片到本地以及更改图片大小

1.存储图片到磁盘
NSData *imageData = UIImageJPEGRepresentation(image, 0.7);
NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *totalPath = [documentPath stringByAppendingString:@"/avatar.jpg"];
[imageData writeToFile:totalPath atomically:YES];

2.改变图片大小

• (UIImage *)imageByScalingAndCroppingForSize:(CGSize)targetSize withSourceImage:(UIImage *)sourceImage{
  UIImage *newImage = nil;
  CGSize imageSize = sourceImage.size;
  CGFloat width = imageSize.width;
  CGFloat height = imageSize.height;
  CGFloat targetWidth = targetSize.width;
  CGFloat targetHeight = targetSize.height;
  CGFloat scaleFactor = 0.0;
  CGFloat scaledWidth = targetWidth;
  CGFloat scaledHeight = targetHeight;
  CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
  if (CGSizeEqualToSize(imageSize, targetSize) == NO) {
  CGFloat widthFactor = targetWidth / width;
  CGFloat heightFactor = targetHeight / height;
  if (widthFactor > heightFactor)
  scaleFactor = widthFactor; // scale to fit height
  else
  scaleFactor = heightFactor; // scale to fit width
  scaledWidth= width * scaleFactor;
  scaledHeight = height * scaleFactor;
  // center the image
  if (widthFactor > heightFactor)
  {
  thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
  }
  else if (widthFactor < heightFactor)
  {
  thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
  }
  }
  UIGraphicsBeginImageContext(targetSize); // this will crop
  CGRect thumbnailRect = CGRectZero;
  thumbnailRect.origin = thumbnailPoint;
  thumbnailRect.size.width= scaledWidth;
  thumbnailRect.size.height = scaledHeight;

  [sourceImage drawInRect:thumbnailRect];
  newImage = UIGraphicsGetImageFromCurrentImageContext();
  if(newImage == nil)
  NSLog(@"could not scale image");

  //pop the context to get back to the default
  UIGraphicsEndImageContext();

  return newImage;
  }