1.等比率縮放

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

2.自定長(zhǎng)寬

- (UIImage *)reSizeImage:(UIImage *)image toSize:(CGSize)reSize{
  UIGraphicsBeginImageContext(CGSizeMake(reSize.width, reSize.height));
  [image drawInRect:CGRectMake(0, 0, reSize.width, reSize.height)];
  UIImage *reSizeImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return reSizeImage;
}

3.處理某個(gè)特定View
只要是繼承UIView的object 都可以處理
必須先import QuzrtzCore.framework

-(UIImage*)captureView:(UIView *)theView{
  CGRect rect = theView.frame;
  UIGraphicsBeginImageContext(rect.size);
  CGContextRef context = UIGraphicsGetCurrentContext();
  [theView.layer renderInContext:context];
  UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return img;
}

4.儲(chǔ)存圖片
儲(chǔ)存圖片這里分成儲(chǔ)存到app的文件里和儲(chǔ)存到手機(jī)的圖片庫(kù)里

1. 儲(chǔ)存到app的文件里

NSString *path = [[NSHomeDirectory()stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:@"image.png"];
[UIImagePNGRepresentation(image) writeToFile:pathatomically:YES];

把要處理的圖片, 以image.png名稱存到app home下的Documents目錄里
2)儲(chǔ)存到手機(jī)的圖片庫(kù)里(必須在真機(jī)使用，模擬器無(wú)法使用)

CGImageRef screen = UIGetScreenImage();
UIImage* image = [UIImage imageWithCGImage:screen];
CGImageRelease(screen);
UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);
UIGetScreenImage(); // 原來(lái)是private(私有)api, 用來(lái)截取整個(gè)畫(huà)面,不過(guò)SDK 4.0后apple就開(kāi)放了

轉(zhuǎn)載：http://blog.csdn.net/xuhuan_wh/article/details/6434055
SDWebImage:異步緩存加載網(wǎng)絡(luò)圖片 http://hao.jobbole.com/sdwebimage-ios/?utm_source=hao.jobbole.com&utm_medium=relatedResources