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
儲存圖片這里分成儲存到app的文件里和儲存到手機的圖片庫里
- 儲存到app的文件里
NSString *path = [[NSHomeDirectory()stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:@"image.png"];
[UIImagePNGRepresentation(image) writeToFile:pathatomically:YES];
把要處理的圖片, 以image.png名稱存到app home下的Documents目錄里
2)儲存到手機的圖片庫里(必須在真機使用，模擬器無法使用)
CGImageRef screen = UIGetScreenImage();
UIImage* image = [UIImage imageWithCGImage:screen];
CGImageRelease(screen);
UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);
UIGetScreenImage(); // 原來是private(私有)api, 用來截取整個畫面,不過SDK 4.0后apple就開放了
//====================================================================================
以下代碼用到了Quartz Framework 和 Core Graphics Framework. 在workspace的framework目錄里添加這兩個framework.在UIKit里，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，使得在不同的坐標系里操作圖像非常方便。缺點就是，獲取圖像的數據不是那么方便。下面會給出獲取數據區的代碼。
- 從UIView中獲取圖像相當于窗口截屏。
(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];
- 對于特定UIView的截屏。
（可以把當前View的layer，輸出到一個ImageContext中，然后利用這個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;
}
- 如果需要裁剪指定區域。
（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。
（分別存儲到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];
若要存儲到圖片庫里面
UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
- 互相轉換UImage和CGImage。
（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）
下面給出一個在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;
}
- 顯示圖像數據區。
（顯示圖像數據區，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);
