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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。
- CGImageRef screen = UIGetScreenImage();
- 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
- -(UIImage*)captureView: (UIView *)theView
- {
- CGRect rect = theView.frame;
- UIGraphicsBeginImageContext(rect.size);
- CGContextRef context =UIGraphicsGetCurrentContext();
- [theView.layer renderInContext:context];
- UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
- UIGraphicsEndImageContext();
-
- return img;
- }
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
- UIGraphicsBeginImageContext(CGMakeSize(200,200));
- CGContextRefcontext=UIGraphicsGetCurrentContext();
- UIGraphicsPushContext(context);
- // ...把图写到context中,省略[indent]CGContextBeginPath();
- CGContextAddRect(CGMakeRect(0,0,100,100));
- CGContextClosePath();[/indent]CGContextDrawPath();
- CGContextFlush(); // 强制执行上面定义的操作
- UIImage* image = UIGraphicGetImageFromCurrentImageContext();
- 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
- NSString *path = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"image.png"];
- [UIImagePNGRepresentation(image) writeToFile:path atomically:YES];
若要存储到图片库里面
- UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
UImage封装了CGImage, 互相转换很容易
- UIImage* imUI=nil;
- CGImageRef imCG=nil;
- imUI = [UIImage initWithCGImage:imCG];
- 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
- -(id)invertContrast:(UIImage*)img
- {
- CGImageRef inImage = img.CGImage;
- CGContextRef ctx;
- CFDataRef m_DataRef;
- m_DataRef = CGDataProviderCopyData(CGImageGetDataProvider(inImage));
-
- int width = CGImageGetWidth( inImage );
- int height = CGImageGetHeight( inImage );
-
- int bpc = CGImageGetBitsPerComponent(inImage);
- int bpp = CGImageGetBitsPerPixel(inImage);
- int bpl = CGImageGetBytesPerRow(inImage);
-
- UInt8 * m_PixelBuf = (UInt8 *) CFDataGetBytePtr(m_DataRef);
- int length = CFDataGetLength(m_DataRef);
-
- NSLog(@"len %d", length);
- NSLog(@"width=%d, height=%d", width, height);
- NSLog(@"1=%d, 2=%d, 3=%d", bpc, bpp,bpl);
-
- for (int index = 0; index < length; index += 4)
- {
- m_PixelBuf[index + 0] = 255 - m_PixelBuf[index + 0];// b
- m_PixelBuf[index + 1] = 255 - m_PixelBuf[index + 1];// g
- m_PixelBuf[index + 2] = 255 - m_PixelBuf[index + 2];// r
- }
-
- ctx = CGBitmapContextCreate(m_PixelBuf, width, height, bpb, bpl, CGImageGetColorSpace( inImage ), kCGImageAlphaPremultipliedFirst );
- CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
- UIImage* rawImage = [UIImage imageWithCGImage:imageRef];
- CGContextRelease(ctx);
- return rawImage;
- }
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
- CGContextRef ctx = CGBitmapContextCreate(pixelBuf,width,height, bitsPerComponent,bypesPerLine, colorSpace,kCGImageAlphaPremultipliedLast );
- CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
- UIImage* image = [UIImage imageWithCGImage:imageRef];
- NSString* path = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"ss.png"];
- [UIImagePNGRepresentation(self.image) writeToFile:path atomically:YES];
- CGContextRelease(ctx);
關於圖像獲取方麵,在這裏應該都覆蓋到了,不正之處,歡迎指正。
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