UIImage 图片处理:截图,缩放,设定大小,存储
图片的处理大概分 截图(capture), 缩放(scale), 设定大小(resize), 存储(save)
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的文件里和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];
把要处理的图片, 以image.png名称存到app home下的Documents目录里
2)储存到手机的图片库里(必须在真机使用,模拟器无法使用)
CGImageRef screen = UIGetScreenImage(); UIImage* image = [UIImage imageWithCGImage:screen]; CGImageRelease(screen); UIImageWriteToSavedPhotosAlbum(image, self, nil, nil); UIGetScreenImage(); // 原来是private(私有)api, 用来截取整个画面,不过SDK 4.0后apple就开放了
//====================================================================================
以下代码用到了Quartz Framework 和 Core Graphics Framework. 在workspace的framework目录里添加这两个framework.在UIKit里,图像类UIImage和CGImageRef的画图操作都是通过Graphics Context来完成。Graphics Context封装了变换的参数,使得在不同的坐标系里操作图像非常方便。缺点就是,获取图像的数据不是那么方便。下面会给出获取数据区的代码。
1. 从UIView中获取图像相当于窗口截屏。
(iOS提供全局的全屏截屏函数UIGetScreenView(). 如果需要特定区域的图像,可以crop一下)
CGImageRef screen = UIGetScreenImage();
UIImage* image = [UIImage imageWithCGImage:screen];
2. 对于特定UIView的截屏。
(可以把当前View的layer,输出到一个ImageContext中,然后利用这个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; }
3. 如果需要裁剪指定区域。
(可以path & clip,以下例子是建一个200x200的图像上下文,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();
4. 存储图像。
(分别存储到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);
5. 互相转换UImage和CGImage。
(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;
6. 从CGImage上获取图像数据区。
(在apple dev上有QA, 不过好像还不支持ios)
下面给出一个在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; }
7. 显示图像数据区。
(显示图像数据区,也就是unsigned char*转为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);