UIImage 图片处理:截图,缩放,设定大小,存储

2011/06/21 15:35
阅读数 2W

图片的处理大概就分 截图(capture), 缩放(scale),设定大小(resize), 存储(save)
这几样比较好处理, 另外还有滤镜,擦试等, 以后再说
在这个Demo code裡, 我写了几个方法


1.等比率缩放
- (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.自定长宽
- (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.处理某个特定View
只要是继承UIView的object 都可以处理
必须先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.储存图片
储存图片这里分成储存到app的文件里, 储存到手机的图片库里

1) 储存到app的文件里
NSString *path = [[NSHomeDirectory()stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:@"image.png"];
[UIImagePNGRepresentation(image) writeToFile:pathatomically:YES];
這樣就把你要處理的圖片, 以image.png這個檔名存到app home底下的Documents目錄裡

2)储存到手机的图片库里
CGImageRef screen = UIGetScreenImage();
UIImage* image = [UIImage imageWithCGImage:screen];
CGImageRelease(screen);
UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);
UIGetScreenImage()原本是private(私有)api, 用來截取整個畫麵
不過SDK 4.0後apple就開放了

另外儲存到手機的圖片庫裡, 必須在實機使用, 模擬器無法使用


以下代碼用到了Quartz Framework和Core Graphics Framework. 在workspace的framework目錄裏添加這兩個framework.在UIKit裏,圖像類UIImage和CGImageRef的畫圖操作都是通過Graphics Context來完成。Graphics Context封裝了變換的參數,使得在不同的坐標係裏操作圖像非常方便。缺點就是,獲取圖像的數據不是那麼方便。下麵會給出獲取數據區的代碼。



從UIView中獲取圖像相當於窗口截屏。ios提供全局的全屏截屏函數UIGetScreenView(). 如果需要特定區域的圖像,可以crop一下。

  1. CGImageRef screen = UIGetScreenImage();
  2. UIImage* image = [UIImage imageWithCGImage:screen];

對於特定UIView的截屏,可以把當前View的layer,輸出到一個ImageContext中,然後利用這個ImageContext得到UIImage

  1. -(UIImage*)captureView: (UIView *)theView
  2. {
  3. CGRect rect = theView.frame;
  4. UIGraphicsBeginImageContext(rect.size);
  5. CGContextRef context =UIGraphicsGetCurrentContext();
  6. [theView.layer renderInContext:context];
  7. UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
  8. UIGraphicsEndImageContext();

  9. return img;
  10. }

如果需要裁剪製定區域,可以path & clip,以下例子是建一個200x200的圖像上下文,再截取出左上角

  1. UIGraphicsBeginImageContext(CGMakeSize(200,200));
  2. CGContextRefcontext=UIGraphicsGetCurrentContext();
  3. UIGraphicsPushContext(context);
  4. // ...把图写到context中,省略[indent]CGContextBeginPath();
  5. CGContextAddRect(CGMakeRect(0,0,100,100));
  6. CGContextClosePath();[/indent]CGContextDrawPath();
  7. CGContextFlush();  // 强制执行上面定义的操作
  8. UIImage* image = UIGraphicGetImageFromCurrentImageContext();
  9. UIGraphicsPopContext();

存储图像分为存储到home目录文件和图片库文件。存储到目录文件是这样

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

若要存储到图片库里面

  1. UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);


UImage封装了CGImage, 互相转换很容易

  1. UIImage* imUI=nil;
  2. CGImageRef imCG=nil;
  3. imUI = [UIImage initWithCGImage:imCG];
  4. imCG = imUI.CGImage;

從CGImage上獲取圖像數據區,在apple dev上有QA, 不過好像還不支持ios
下麵給出一個在ios上反色的例子

  1. -(id)invertContrast:(UIImage*)img
  2. {
  3. CGImageRef inImage = img.CGImage; 
  4. CGContextRef ctx;
  5. CFDataRef m_DataRef;
  6. m_DataRef = CGDataProviderCopyData(CGImageGetDataProvider(inImage)); 

  7. int width = CGImageGetWidth( inImage );
  8. int height = CGImageGetHeight( inImage );

  9. int bpc = CGImageGetBitsPerComponent(inImage);
  10. int bpp = CGImageGetBitsPerPixel(inImage);
  11. int bpl = CGImageGetBytesPerRow(inImage);

  12. UInt8 * m_PixelBuf = (UInt8 *) CFDataGetBytePtr(m_DataRef);
  13. int length = CFDataGetLength(m_DataRef);

  14. NSLog(@"len %d", length);
  15. NSLog(@"width=%d, height=%d", width, height);
  16. NSLog(@"1=%d, 2=%d, 3=%d", bpc, bpp,bpl);

  17. for (int index = 0; index < length; index += 4)
  18. m_PixelBuf[index + 0] = 255 - m_PixelBuf[index + 0];// b
  19. m_PixelBuf[index + 1] = 255 - m_PixelBuf[index + 1];// g
  20. m_PixelBuf[index + 2] = 255 - m_PixelBuf[index + 2];// r
  21. }

  22. ctx = CGBitmapContextCreate(m_PixelBuf, width, height, bpb, bpl, CGImageGetColorSpace( inImage ), kCGImageAlphaPremultipliedFirst );
  23. CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
  24. UIImage* rawImage = [UIImage imageWithCGImage:imageRef];
  25. CGContextRelease(ctx);
  26. return rawImage;
  27. }

得到圖像數據區後就可以很方便的實現圖像處理的算法。下麵給顯示圖像數據區的方法,也就是unsigned char*轉為graphics context或者UIImage或和CGImageRef

  1. CGContextRef ctx = CGBitmapContextCreate(pixelBuf,width,height, bitsPerComponent,bypesPerLine, colorSpace,kCGImageAlphaPremultipliedLast );
  2. CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
  3. UIImage* image = [UIImage imageWithCGImage:imageRef];
  4. NSString* path = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"ss.png"];
  5. [UIImagePNGRepresentation(self.image) writeToFile:path atomically:YES];
  6. CGContextRelease(ctx);
展开阅读全文
加载中
点击引领话题📣 发布并加入讨论🔥
打赏
0 评论
10 收藏
0
分享
返回顶部
顶部