UIImage 图片处理：截图，缩放，设定大小，存储

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。

转自：/article/4221963.html