圖片的處理大概就分 截圖(capture), 縮放(scale),設定大小(resize), 存儲(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
儲存圖片這裏分成儲存到app的文件裏, 儲存到手機的圖片庫裏
1) 儲存到app的文件裏
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裏
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();
存儲圖像分爲存儲到home目錄文件和圖片庫文件。存儲到目錄文件是這樣
NSString *path = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"image.png"];
[UIImagePNGRepresentation(image) writeToFile:path atomically:YES];
若要存儲到圖片庫裏面
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。