UIImage 圖片處理：截圖，縮放，設定大小，儲存

圖片的處理大概就分截圖(capture), 縮放(scale),設定大小(resize), 儲存(save)

這幾樣比較好處理, 另外還有濾鏡,擦試等, 以後再說

在這個Demo code裡, 我寫了幾個方法

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.儲存圖片

儲存圖片這裡分成儲存到app的檔案裡, 儲存到手機的圖片庫裡

1) 儲存到app的檔案裡

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)儲存到手機的圖片庫裡

CGImageRef screen = UIGetScreenImage();

UIImage* image = [UIImage imageWithCGImage:screen];

CGImageRelease(screen);

UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);

UIGetScreenImage()原本是private(私有)api, 用來擷取整個畫麵

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

以下程式碼用到了Quartz Framework和Core Graphics Framework. 在workspace的framework目錄裡新增這兩個framework.在UIKit裡，影象類UIImage和CGImageRef的畫圖操作都是通過Graphics Context來完成。Graphics Context封裝了變換的引數，使得在不同的坐標係裡操作影象非常方便。缺點就是，獲取影象的資料不是那麼方便。下麵會給出獲取資料區的程式碼。

從UIView中獲取影象相當於視窗截圖。ios提供全域性的全屏截圖函式UIGetScreenView(). 如果需要特定區域的影象，可以crop一下。

CGImageRef screen = UIGetScreenImage();

UIImage* image = [UIImage imageWithCGImage:screen];

對於特定UIView的截圖，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的影象上下文，再擷取出左上角

UIGraphicsBeginImageContext(CGMakeSize(200,200));

CGContextRefcontext=UIGraphicsGetCurrentContext();

UIGraphicsPushContext(context);

// ...把圖寫到context中，省略[indent]CGContextBeginPath();

CGContextAddRect(CGMakeRect(0,0,100,100));

CGContextClosePath();[/indent]CGContextDrawPath();

CGContextFlush(); // 強制執行上面定義的操作

UIImage* image = UIGraphicGetImageFromCurrentImageContext();

UIGraphicsPopContext();

儲存影象分為儲存到home目錄檔案和圖片庫檔案。儲存到目錄檔案是這樣

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

[UIImagePNGRepresentation(image) writeToFile:path atomically:YES];

若要儲存到圖片庫裡面

UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);

UImage封裝了CGImage, 互相轉換很容易

UIImage* imUI=nil;

CGImageRef imCG=nil;

imUI = [UIImage initWithCGImage:imCG];

imCG = imUI.CGImage;

從CGImage上獲取影象資料區，在apple dev上有QA, 不過好像還不支援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;

}

得到影象資料區後就可以很方便的實現影象處理的演算法。下麵給顯示影象資料區的方法，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);

關於影象獲取方麵，在這裡應該都覆蓋到了，不正之處，歡迎指正。

UIImage 圖片處理：截圖，縮放，設定大小，儲存

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