1.截取当前屏幕

  CGSize windowSize = behandView.bounds.size;
    UIGraphicsBeginImageContextWithOptions(windowSize, YES, 2.0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [behandView.window.layer renderInContext:context];
    UIImage *snapshot = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

2.截屏-scrollview

- (UIImage *)captureScrollView:(UIScrollView *)scrollView{
        UIImage* image = nil;
        UIGraphicsBeginImageContextWithOptions(scrollView.contentSize, NO, 2.0f);
        {
            CGPoint savedContentOffset = scrollView.contentOffset;
            CGRect savedFrame = scrollView.frame;
            scrollView.contentOffset = CGPointZero;
            scrollView.frame = CGRectMake(0, 0, scrollView.contentSize.width, scrollView.contentSize.height);
            
            [scrollView.layer renderInContext: UIGraphicsGetCurrentContext()];
            image = UIGraphicsGetImageFromCurrentImageContext();
            
            scrollView.contentOffset = savedContentOffset;
            scrollView.frame = savedFrame;
        }
        UIGraphicsEndImageContext();
        
        if (image != nil)
        {
            return image;
        }

3.扩展知识，UIImage的绘制和渲染

UIGraphicsBeginImageContext系列知识

UIGraphicsBeginImageContext
创建一个基于位图的上下文（context）,并将其设置为当前上下文(context)。方法声明如下：

 
 void UIGraphicsBeginImageContext(CGSize size);

参数size为新创建的位图上下文的大小。它同时是由UIGraphicsGetImageFromCurrentImageContext函数返回的图形大小。
该函数的功能同UIGraphicsBeginImageContextWithOptions的功能相同，相当与UIGraphicsBeginImageContextWithOptions的opaque参数为NO,scale因子为1.0。

UIGraphicsBeginImageContextWithOptions
函数原型为：

 void UIGraphicsBeginImageContextWithOptions(CGSize size, BOOL opaque, CGFloat scale); 

size——同UIGraphicsBeginImageContext
opaque—透明开关，如果图形完全不用透明，设置为YES以优化位图的存储。
scale—–缩放因子

默认创建一个透明的位图上下文

UIImageC处理

1、等比缩放

C代码

1. - (UIImage *) scaleImage:(UIImage *)image toScale:(float)scaleSize {
2. UIGraphicsBeginImageContext(CGSizeMake(image.size.width * scaleSize, image.size.height * scaleSize);
3. [image drawInRect:CGRectMake(0, 0, image.size.width * scaleSize, image.size.height * scaleSize)];
4. UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
5. UIGraphicsEndImageContext();
6. return scaledImage;
7. }

2、自定义大小

C代码

1. - (UIImage *) reSizeImage:(UIImage *)image toSize:(CGSize)reSize {
2. UIGraphicsBeginImageContext(CGSizeMake(reSize.width, reSize.height));
3. [image drawInRect:CGRectMake(0, 0, reSize.width, reSize.height)];
4. UIImage *reSizeImage = UIGraphicsGetImageFromCurrentImageContext();
5. UIGraphicsEndImageContext();
6. return reSizeImage;
7. }

3、处理某个特定的view

只要是继承UIView的object都可以处理
必须先import QuzrtzCore.framework

C代码

1. -(UIImage*) captureView:(UIView *)theView {
2. CGRect rect = theView.frame;
3. UIGraphicsBeginImageContext(rect.size);
4. CGContextRef context = UIGraphicsGetCurrentContext();
5. [theView.layer renderInContext:context];
6. UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
7. UIGraphicsEndImageContext();
8. return img;
9. }

4、存储图片

4.1、存储到app的文件里

把要处理的图片以image.png的名字存储到apphome地下的Document目录中

C代码

1. NSString *path = [[NSHomeDirectory()stringByAppendingPathComponent:@"Documents"]stringByAppendingPathComponent:@"image.png"];
2. [UIImagePNGRepresentation(image) writeToFile:pathatomically:YES];

4.2、存储到手机的图片库中

1. CGImageRef screen = UIGetScreenImage();
2. UIImage* image = [UIImage imageWithCGImage:screen];
3. CGImageRelease(screen);
4. UIImageWriteToSavedPhotosAlbum(image, self, nil, nil);

获取当前app的名称和版本号

1. NSDictionary *infoDictionary = [[NSBundle mainBundle] infoDictionary];
2. // app名称
3. NSString *name = [infoDictionary objectForKey:@"CFBundleDisplayName"];
4. // app版本
5. NSString *version = [infoDictionary objectForKey:@"CFBundleShortVersionString"];
6. // app build版本
7. NSString *build = [infoDictionary objectForKey:@"CFBundleVersion"];

UILabel根据text自动调整大小

1. label.text = @"**********";
2. CGRect frame = label.frame;
3. frame.size.height = 10000; // 设置一个很大的高度
4. label.frame = frame;
5. [label sizeToFit];
6. frame.size.height = label.frame.size.height;
7. label.frame = frame;

1. [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"tel://01011112222,3333"]];

- (UIImage *)rescaleImage:(UIImage *)imgToSize:(CGSize)size; //图片缩放裁剪

- (UIImage*)transformWidth:(CGFloat)width height:(CGFloat)height;//改变大小

+ (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage*)image2; //合并图片

+ (UIImage *)imageFromImage:(UIImage *)imageinRect:(CGRect)rect; //裁剪部分图片

+ (void)imageSavedToPhotosAlbum:(UIImage *)image

didFinishSavingWithError:(NSError *)errorcontextInfo:(void *)contextInfo; //保存图片到媒体库

零重新设置图片的尺寸

- (UIImage *)rescaleImage:(UIImage *)imgToSize:(CGSize)size {

CGRect rect = CGRectMake(0.0, 0.0, size.width,size.height);

UIGraphicsBeginImageContext(rect.size);

[img drawInRect:rect]; // scales image to rect

UIImage *resImage =UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return resImage;

}

－）根据给定得图片，从其指定区域截取一张新得图片

-(UIImage *)getImageFromImage{

//大图bigImage

//定义myImageRect，截图的区域

CGRect myImageRect = CGRectMake(10.0, 10.0, 57.0, 57.0);

UIImage* bigImage= [UIImageimageNamed:@"k00030.jpg"];

CGImageRef imageRef = bigImage.CGImage;

CGImageRef subImageRef =CGImageCreateWithImageInRect(imageRef, myImageRect);

CGSize size;

size.width = 57.0;

size.height = 57.0;

UIGraphicsBeginImageContext(size);

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextDrawImage(context, myImageRect, subImageRef);

UIImage* smallImage = [UIImageimageWithCGImage:subImageRef];

UIGraphicsEndImageContext();

return smallImage;

}

二） 合并两张图片

- (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage*)image2 {

UIGraphicsBeginImageContext(image1.size);

// Draw image1

[image1 drawInRect:CGRectMake(0, 0, image1.size.width,image1.size.height)];

// Draw image2

[image2 drawInRect:CGRectMake(0, 0, image2.size.width,image2.size.height)];

UIImage *resultingImage =UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

returnresultingImage;

}

三） 捕捉屏幕截图

CALayer实例使用CoreGraphics的renderInContext方法可以将视图绘制到图像上下文中以便转化为其他UIImage实例。前提先#import

+ (UIImage *) imageFromView: (UIView *)theView{     // draw a view‘s contents into animage context   UIGraphicsBeginImageContext(theView.frame.size);    CGContextRef  context = UIGraphicsGetCurrentContext();     [theView.layer  renderInContext:context];    UIImage *theImage =UIGraphicsGetImageFromCurrentImageContext();   UIGraphicsEndImageContext();    return theImage; }

注：UIGraphicsBeginImageContext(CGSize size)创建一个基于位图的上下文(context)，并将其设置为当前上下文。函数功能与UIGraphicsBeginImageContextWithOptions相同，相当于该方法的opaque参数为NO，scale因子为1.0。而UIGraphicsEndImageContext()方法是移除栈顶的基于当前位图的图形上下文。

视图添加倒影效果

const CGFloat kReflectPercent = -0.25f; constCGFloat kReflectOpacity = 0.3f; const CGFloat kReflectDistance = 10.0f;  + (void)addSimpleReflectionToView:(UIView*)theView {      CALayer *reflectionLayer= [CALayer layer];      reflectionLayer.contents= [theView layer].contents;     reflectionLayer.opacity = kReflectOpacity;      reflectionLayer.frame =CGRectMake(0.0f,0.0f,theView.frame.size.width,theView.frame.size.height*kReflectPercent);  //倒影层框架设置，其中高度是原视图的百分比   CATransform3D stransform = CATransform3DMakeScale(1.0f,-1.0f,1.0f);      CATransform3D transform =CATransform3DTranslate(stransform,0.0f,-(kReflectDistance +theView.frame.size.height),0.0f);     reflectionLayer.transform = transform;      reflectionLayer.sublayerTransform =reflectionLayer.transform;      [[theViewlayer] addSublayer:reflectionLayer]; }

另一：使用Core Graphics创建倒影

+ (CGImageRef) createGradientImage:(CGSize)size{       CGFloat colors[] ={0.0,1.0,1.0,1.0};       //在灰色设备色彩上建立一渐变    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();       CGContextRef context =CGBitmapContextCreate(nil,size.width,size.height,8,0,colorSpace,kCGImageAlphaNone);       CGGradientRef gradient =CGGradientCreateWithColorComponents(colorSpace,colors,NULL,2);       CGColorSpaceRelease(colorSpace);        //绘制线性渐变    CGPoint p1 = CGPointZero;      CGPoint p2 = CGPointMake(0,size.height);      CGContextDrawLinearGradient(context,gradient,p1,p2,kCGGradientDrawsAfterEndLocation);        //Return the CGImage      CGImageRef theCGImage =CGBitmapContextCreateImage(context);      CFRelease(gradient);      CGContextRelease(context);      return theCGImage; }

//Create a shrunken frame for the reflection

+ (UIImage *) reflectionOfView:(UIView *)theViewWithPercent:(CGFloat) percent {     //Retain the width but shrink the height     CGSize size =CGSizeMake(theView.frame.size.width, theView.frame.size.height * percent);       //Shrink the View     UIGraphicsBeginImageContext(size);      CGContextRef context =UIGraphicsGetCurrentContext();     [theView.layer renderInContext:context];      UIImage *partialimg =UIGraphicsGetImageFromCurrentImageContext();      UIGraphicsEndImageContext();       //build the mask     CGImageRef mask = [ImageHelpercreateGradientImage:size];     CGImageRef ref = CGImageCreateWithMask(partialimg.CGImage,mask);      UIImage *theImage = [UIImageimageWithCGImage:ref];     CGImageRelease(ref);     CGImageRelease(mask);      returntheImage; }  const CGFloatkReflectDistance = 10.0f; + (void) addReflectionToView: (UIView *)theView{      theView.clipsToBounds = NO;      UIImageView *reflection = [[UIImageViewalloc] initWithImage:[ImageHelper reflectionOfView:theView withPercent:0.45f]];      CGRect frame = reflection.frame;      frame.origin = CGPointMake(0.0f,theView.frame.size.height + kReflectDistance);      reflection.frame = frame;       // add the reflection as a simplesubview     [theViewaddSubView:reflection];      [reflectionrelease]; }

关于图片缩放的线程安全和非线程安全操作.

非线程安全的操作只能在主线程中进行操作,对于大图片的处理肯定会消耗大量的时间,如下面的方法

方法 1： 使用 UIKit

+ (UIImage*)imageWithImage INCLUDEPICTURE"http://www.61ic.com/Mobile/UploadFiles_9667/201103/20110309123315372.gif"\* MERGEFORMATINET UIImage*)image scaledToSize INCLUDEPICTURE"http://www.61ic.com/Mobile/UploadFiles_9667/201103/20110309123315372.gif"\* MERGEFORMATINET CGSize)newSize;

{

// Create a graphics image context

UIGraphicsBeginImageContext(newSize);

// Tell the old image to draw in this new context, withthe desired

// new size

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

// Get the new image from the context

UIImage* newImage =UIGraphicsGetImageFromCurrentImageContext();

// End the context

UIGraphicsEndImageContext();

// Return the new image.

return newImage;

}

此方法很简单， 但是，这种方法不是线程安全的情况下.

方法 2： 使用 CoreGraphics

iOS 截屏以及相关扩展（UIImage的绘制和渲染）