UIImage 相关操作

 

修改UIImage大小

修改UISlider的最大值和最小值图片的时候，发现需要修改图片的大小，否则会导致UISlider变形。目前苹果还不支持直接修改UIImage类的大小，只能修改UIImageView的大小。

所以只能通过写方法的方式来实现修改图片。如下：

 //UIImage.h



#import <Foundation/Foundation.h>



@interface UIImage (Scale)



-(UIImage *)TransformtoSize:(CGSize)Newsize;



@end



//UIImage.m



 



#import "UIImage.h"



@implementation UIImage (Scale)



-(UIImage *)TransformtoSize:(CGSize)Newsize



{



    // 创建一个bitmap的context



    UIGraphicsBeginImageContext(Newsize);



    // 绘制改变大小的图片



    [self drawInRect:CGRectMake(0, 0, Newsize.width, Newsize.height)];



    // 从当前context中创建一个改变大小后的图片



    UIImage *TransformedImg=UIGraphicsGetImageFromCurrentImageContext();



    // 使当前的context出堆栈



    UIGraphicsEndImageContext();



    // 返回新的改变大小后的图片



    return TransformedImg;



}



@end



最后在其他地方导入头文件，即可以使用此方法了。



 



UIImage *MaxImg=[UIImage imageNamed:@"sunny.png"];



UIImage *MaxImg_Fin=[MaxImg TransformtoSize:CGSizeMake(28, 28)];

 

调整UIImage尺寸适应UIImageView

+ (UIImage*)imageWithImage:(UIImage*)image 

               scaledToSize:(CGSize)newSize;

{

   UIGraphicsBeginImageContext( newSize );

   [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];

   UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();

   UIGraphicsEndImageContext();



   return newImage;

}

指定新尺寸(768,1024) 然后传递初始图片，但是要保证高宽比和原始的比例一样。

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http://my.oschina.net/rareliu/blog/24322

UIImage 图片处理：截图，缩放，设定大小，存储
发表于3年前(2011-06-21 15:35)

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);