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);